Abstract
Background:
The Children’s Oncology Group defines intermediate-risk rhabdomyosarcoma (IR-RMS) as patients who have unresected FOXO1 fusion negative disease arising at an unfavorable site or those with non-metastatic FOXO1 fusion positive disease. Temsirolimus (TEM) in combination with chemotherapy has shown promising activity in patients with relapsed and refractory RMS. The primary objective of this phase 3 trial was to compare the event-free survival (EFS) of patients with IR-RMS treated with vincristine, actinomycin, cyclophosphamide alternating with vincristine and irinotecan (VAC-VI) combined with TEM followed by maintenance therapy with vinorelbine plus low dose cyclophosphamide versus VAC-VI alone with maintenance.
Methods:
ARST1431 was a prospective, randomized, multi-center, open label study. Randomization occurred electronically. Eligible patients were those ≤ age 40 years with non-metastatic FOXO1 positive RMS or unresected FOXO1 negative RMS disease from unfavorable sites. In addition, 2 other groups of patients were also eligible: a) those who had disease at a favorable site which was unresected and b) those who were <10 years of age with stage IV FOXO1 negative disease. Lansky performance status score was ≥ 50 for patients ≤ 16 years of age and Karnofsky performance status score ≥ 50 for patients >16 years of age; all were previously untreated. Patients received VAC/VI chemotherapy with a cyclophosphamide dose of 1.2 g/m2/dose per cycle with (Arm B) or without TEM (Arm A) at a starting dose of 15 mg/m2 weekly. Total duration of therapy was 42 weeks (intravenous) followed by 6 months of maintenance therapy for all patients with oral cyclophosphamide plus IV vinorelbine. TEM was held during radiation therapy (RT). The primary endpoint was 3-year EFS with analysis. The data was analyzed with revised intention-to-treat approach. The study is registered with ClinicalTrials.gov, number NCT02567435, and is complete.
Findings:
Between May 2016 and Jan 2022, 325 patients were enrolled. Of 297 evaluable patients (148 in Arm A and 149 in Arm B), median age was 6.33 years (range 0.04 to 35.8); 38 subjects were ≥16 years of age; 179 (60%; 179 of 297) were male. In Arm A and B, 113 of 148 (76.9%) and 108 of 149 (73.0%) were FOXO1 negative, respectively. With a median follow-up time of 3.57 years (IQR 2.80 to 4.51 years), 3-year EFS of the VAC/VI arm was 64.8% (95% CI: (55.5%, 74.1%)) compared to 66.8% (95% CI: (57.5%, 76.2%)) for VAC/VI plus TEM (log-rank p=0.44; HR 0.86 (95% CI: (0.58, 1.26)). The most common grade 3–4 adverse events were anemia (62 (41.9%) of 148 in Arm A and 89 (59.7%) of 149 in ArmB), lymphopenia (83 (56.1%) in Arm A and 99 (66.4%) in Arm B, neutropenia (100% in both arms), leukopenia (121(81.8%) in Arm A and 132(88.6%) in Arm B), There was one treatment related death in Arm B.
Interpretation:
Addition of TEM to VAC/VI failed to improve outcome in patients with intermediate-risk RMS defined by their FOXO1 translocation status and clinical factors.
Introduction
Rhabdomyosarcoma (RMS) is the most common soft tissue sarcoma in young people wherein outcome is defined by primary site, presence or absence of distant metastases, the extent of primary upfront resection and translocation status of the FOXO1 gene. The 2020 World Health Organization classification distinguishes four histological subtypes of RMS - embryonal, alveolar, spindle cell/sclerosing, and pleomorphic - wherein alveolar subtypes are associated with the FOXO1 translocation in over 80% of cases. (1, 2) Risk categorization of RMS is based on expected outcomes, and those with intermediate-risk (IR) have an expected event-free survival (EFS) approaching 65% at 3 years. (3–5)
In a seminal study, patients with first relapse RMS were randomized to receive IV cyclophosphamide plus vinorelbine with either temsirolimus (TEM), an mTOR inhibitor, or bevacizumab (BEV). (6) Patients in the TEM arm had superior 6-month event-free survival (p=0.0031) as compared to the BEV arm suggesting a role for targeting the mTOR pathway inhibition in this disease. Preclinical data in mouse RMS (7) and xenograft (8, 9) models of RMS similarly demonstrated activity of mTOR inhibition.
To improve outcomes in patients with IR RMS, we sought to examine the benefit of adding TEM to a chemotherapy backbone comprising cassettes of vincristine, actinomycin and cyclophosphamide (VAC) alternating with vincristine plus irinotecan (VI). (10) The feasibility of combining TEM with VAC/VI chemotherapy was evaluated in a preliminary safety study confirming that 15 mg/m2 weekly in combination with VAC/VI is safe. (3) Based on this data, we conducted a randomized phase 3 study in IR-RMS with VAC/VI followed by maintenance versus VAC/VI plus TEM followed by maintenance as first-line therapy. The primary objective was to compare EFS between the two treatment arms.
Methods
Study Design and Participants
We conducted this phase 3 study through the Children’s Oncology Group (COG) and enrolled patient from 210 institutions in USA, Canada, New Zealand, and Australia. To be eligible, patients had to be ≤40 years of age with FOXO1 positive non-metastatic disease (Stage 1–3, Group I-III),(11) any FOXO1 negative disease arising from an unfavorable site (Stage 2/3, Group III), unresected FOXO1 negative disease arising from a favorable site (excluding orbit) (Stage 1, Group III) or FOXO1 negative disease with distant metastases (Group IV, ≤10 years of age). Patients were required to have a Lansky performance status score ≥ 50 for patients ≤ 16 years of age and Karnofsky performance status score ≥ 50 for patients >16 years of age. Sex and ethnicity were defined via self-report. Nodal sampling was mandatory for patients with paratesticular disease (if age ≥ 10 years) and for patients of any age with extremity tumors, regardless of histology. Confirmation of FOXO1 status within 3 weeks of enrollment was required to maintain enrollment. All patients were required to submit adequate specimens to complete central pathology review. Tumor histology was confirmed as non-pleomorphic RMS by central review. FOXO1 status was assessed at local institutions and confirmed centrally for the first 100 patients with 99% concordance rate between central testing and local institution. Patients were excluded if they had previously received TEM, or another mTOR inhibitor, or any other investigational agent or chemotherapy (excluding steroids). Patients were also excluded if they had received radiation therapy (RT) prior to enrollment or had evidence of uncontrolled hyperglycemia or hyperlipidemia. Patients who were sexually active and of reproductive potential and chose not to use an effective contraceptive method for the duration of their study participation, as well as those who were pregnant or lactating, were also excluded. All patients (or guardians) provided written informed consent and assent when applicable. The study protocol was approved by independent ethics committees and all relevant institutional review boards for each study site.
Randomization and Masking
Patients were randomly assigned (1:1) to receive VAC/VI alone (Arm A) or VAC/VI with TEM (Arm B). Randomisation was done in blocks of four and stratified by histology, stage and group. The four stratums are (EMRS Stage 3, Group I/II OR Stage 1, Group III (non-orbit); EMRS Stage 2/3, Group III; EMRS Stage 4, Group IV, <10 years old; ARMS Stages 1–3, Groups I-III). Neither patients nor investigators were masked to treatment assignment. Because of the open-label trial design, the patients, investigators, and the study sponsor were not masked to the study treatment.
Procedures
The safety of combining TEM with chemotherapy was tested initially in the first 10 non-randomized patients with a dose of 15 mg/m2 IV weekly deemed to be feasible. Patients in Arm A (VAC/VI) and B (VAC/VI with TEM) received the following IV chemotherapy: vincristine sulfate, actinomycin, cyclophosphamide alternating with vincristine and irinotecan every 3 weeks for a total of 14 cycles (42 weeks) followed by 6 cycles of maintenance therapy including oral cyclophosphamide (continuous dosing 28 days) plus IV vinorelbine tartrate (weekly day 1, 8, 15 every 28 days). (see Appendix 1 for dosing details) Patients in Arm B also received concurrent TEM at 15 mg/m2/dose or 0.5 mg/kg/dose for pt < 10 kg IV once weekly except during RT. TEM was held from week 13–20 with RT delivered between weeks 13–18 of protocol treatment. TEM was also held for 2 weeks prior to any major surgical procedure. Delayed primary excision (DPE) of the primary tumor was permitted on both arms after 9 weeks of chemotherapy as per physician discretion when gross total resection was feasible with negative margins and without significant functional compromise. The dose of RT was then determined by the size of the original tumor and the resulting disease status of the primary tumour following 12 weeks of chemotherapy with or without an operation. (see Appendix 2 for RT dosing table)
The following were recorded as dose limiting toxicities (DLT) for TEM: grade ≥ 3 mucositis, grade ≥ 3 pulmonary events, grade 3 hyperglycemia (requiring hospitalization for control), grade ≥ 4 hyperglycemia, grade ≥ 4 cholesterol high (hypercholesterolemia) or hypertriglyceridemia that does not return to ≤ grade 2 levels with appropriate medical management within 35 days, or grade ≥ 3 proteinuria. Patients who experienced pulmonary events, hyperglycemia, or proteinuria as described above had dose modification of TEM as follows: if toxicity resolved to baseline or grade 1 before the next cycle of therapy, then TEM resumed at 100% (full) dose in subsequent cycles unless otherwise specified; if patients experienced the same non-hematological DLT for a second time, the TEM was reduced by one dose level (see Appendix 3). In patients who experienced the same DLT again (3rd time), TEM was modified to Days 1 and 8 only with Day 15 held and then were maintained on this new schedule for all subsequent therapy; patients who experienced the same DLT again (4th time) remained on study but discontinued TEM and received VAC/VI only; if for any reason toxicity did not resolve by the scheduled start date of the next cycle, then the TEM dose was reduced to the next dose level. In all cases, TEM was held until toxicity resolved to baseline or Grade 1, but the remainder of chemotherapy (VAC or VI or V) continued as planned. An aggressive regimen was strongly recommended to help manage mucositis especially in patients receiving TEM but was offered to all patients and included xyloxylin (1:1:1 ratio) (diphenhydramine, aluminum hydroxide and magnesium hydroxide suspension,, lidocaine) 10 mL swish/swallow 4 times daily as needed, calcium phosphate solution (saliva substitute) 15 mL swish/spit every 4 hours as needed, Biotene mouth wash every 4 hours as needed and sucralfate 1 g/10 mL 10 mL swish/swallow or spit 4 times daily as needed. Myeloid growth factor support was offered after VAC cycle. All toxicities >=grade 2 were recorded. Physical exam/weight /height, CBC with differential, total bilirubin, ALT, creatinine were performed on day 1 of every cycle. CBC was performed weekly. Tumor assessments were performed by CT or MRI after 3 cycles of chemotherapy and selected patients were offered DPE of their tumour if gross total resection with negative margins was thought to be possible. Patients who underwent surgery then required post-operative CT or MRI. RT was then offered concurrently with cycle 5 and 6 of chemotherapy – actinomycin D and TEM were held during RT. Further tumor evaluations with CT and/or MRI occurred following cycles 10 and 14, and twice during maintenance therapy (after month 3 and month 6). Follow-up was continued in a graduated manner up to 10 years.
Safety was assessed by recording all adverse events >=grade 3 (including hematological toxicity) using the Common Terminology Criteria for Adverse Events version 5.0, clinical investigations, and physical examination. Patients were removed from protocol therapy if they experienced progressive disease or relapse, unacceptable toxicity due to protocol therapy, refusal of further protocol therapy by patient/parent/guardian, physician determines it is in patient’s best interest, development of a second malignancy, FOXO1 fusion positive with Group IV/Stage 4 disease, FOXO1 fusion status not determined by the institution by Day 21, patient’s start date of protocol therapy is greater than 42 days from the date of the collection of the material that established the diagnosis of RMS. Patients who are off protocol therapy were followed until death, lost to follow-up, patient enrollment onto another COG study with tumor therapeutic intent (eg, at recurrence), withdrawal of consent for any further data submission.
Outcomes
The primary outcome was EFS, defined as time from study enrollment to the first occurrence of progression, relapse, second malignant neoplasm, death from any cause, or time to last contact for those without a prior event. Progression or relapse documentation was performed only by institutional review. Secondary endpoints included comparison of overall survival (OS) between the 2 arms. Overall survival (OS) was defined as the time from enrollment to last contact or death. Exploratory aims included a) to compare the outcome of patients based on their FOXO1 fusion gene partner, by evaluating PAX3 vs. PAX7 in all patients found to be FOXO1 fusion positive, b) to compare the outcome of patients based on their [F18]-fluorodeoxy-D-glucose-positron emission tomography (FDG-PET) response at Week 9 (positive or negative), as assessed by Deauville Criteria (5-point), c) to estimate the frequency of patients with circulating tumor DNA (ctDNA) at diagnosis and subsequent time-points, and explore whether tumor-specific somatic variants are detectable in the ctDNA, d) to compare the outcome of patients (VAC/VI with or without temsirolimus) who have received maintenance therapy on ARST1431 to those who received VAC/VI on ARST0531. The data for the exploratory outcomes will be reported in future manuscripts.
Early during the course of the study, an amendment was approved to add 6 months of maintenance therapy. Patients who did not receive maintenance therapy (ie. those randomized prior to amendment) were excluded from final analyses.
Statistical Analysis
Demographic and clinical characteristics were summarized by treatment arms. Categorical variables Age (0–9, 10–17, 18+ years), sex (Male, Female), histology (Alveolar, Embryonal, Spindle Cell, Other), Primary site (Orbit, Head&Neck nonPM, PM, GU Non-Bladder, GU Bladder, Extremity, Intrathoracic, Perineum-Anus, Retroperitoneum, Trunk, Other), Group(I, II, III, IV), Fusion (FOX01-,PAX3,PAX7,PAX Other) and DPE were summarized using frequency and percentage. Age was also summarized as a continuous variables using median and IQR. The sample size for this study was driven by the primary comparison of EFS with an expected outcome for patients randomized to VAC/VI of 60% EFS at 3 years. (10) The study was designed to have power of 0.84 (testing at a 1-sided 0.05 Type I level; only improvement with the addition of TEM is of interest) to detect an overall increase in the 3-year EFS from 60% to 74%, an absolute difference in the 3-year EFS of 14%, or a relative risk of failure of 0.59 for comparing VAC/VI with TEM to VAC/VI only. A total of 282 patients and 101 observed events were required to attain the power of 0.84 to detect a relative risk of 0.59:1.00 assuming the property of proportional hazards holds. The EFS and OS distributions were estimated using the Kaplan-Meier method and were compared between the randomized treatment groups using the log-rank test. The data was analyzed for EFS, OS and toxicity with revised intention-to-treat approach where 13 patients were excluded post randomization who were not eligible/evaluable due to missing FOXO1 results or who did not receive maintenance therapy (due to an amendment added during the study). There is no evidence to support a significant effect of informative censoring. Among the censored observations only 3 were lost to follow up as of 09/30/2023(2 Arm A, 1 Arm B). The lost to follow up reasons are ‘Patient is lost to follow up; never returned after reaching age of majority.’, ‘Patient lost KP insurance’. One patient did not give the reason. Post-hoc subgroup analyses were conducted to assess treatment effect in age and FOXO1 status subgroups. Cox proportional model was used to test the interaction term. Proportional hazard assumption was assessed and found to be valid. Non-Hematological toxicity, hematological toxicity, cycle length and dose modifications were summarized. The study was monitored by the COG Data and Safety Monitoring Committee. Interim efficacy monitoring of outcome were conducted when 57 and 74 events were observed in fall 2021 and spring 2022. Efficacy was monitored using the O’Brien-Fleming-type cumulative error spending function. The two tests did not reach the significance level (pre- set p-values at 0.0093 and 0.0219) and thus failed to reject the null hypothesis (no improvement in EFS with addition of temsirolimus). The hazard ratio 0.95 and 0.84 were below 1 and didn’t trigger the futility monitoring rule. Patient follow-up was current through September 30, 2023. Statistical analyses were done using SAS version 9.4. This study is registered with ClinicalTrials.gov, number NCT02567435. The CONSORT reporting guidelines were used to prepare this manuscript. (12)
Role of the funding source
The funder of the study had no role in study design, data collection, data analysis, data interpretation, or writing of the report.
Results
Recruitment started on 05/23/2016 until 01/01/2022 during which time, 325 patients were enrolled from 4 countries. Data analysis cut off is 9/30/2023. The outcome analyses presented are based on 297 evaluable patients who were randomised; 147 to VAC/VI followed by maintenance (Arm A) and 147 to VAC/VI plus TEM followed by maintenance (Arm B). (see Figure 1, CONSORT diagram) Three patients were randomized but did not receive treatment. Baseline characteristics in the 2 treatment groups are shown in Table 1.
Figure 1.
CONSORT diagram
Table 1.
Demographic Data
| Treatment | |||
|---|---|---|---|
| Arm A (N=148) | Arm B (N=149) | Total (N=297) | |
| Age (years), Median (IQR) | 6.7 (2.9, 11.1) | 6.1 (3.0, 11.6) | 6.3 (3.0, 11.3) |
| Age (years), n (%) | |||
| 0–9 | 98 (66%) | 99 (66%) | 197 (66%) |
| 10–17 | 38 (26%) | 29 (20%) | 67 (23%) |
| 18+ | 12 (8%) | 21 (14%) | 33 (11%) |
| Gender, n (%) | |||
| Male | 82 (55%) | 97 (65%) | 179 (60%) |
| Female | 66 (45%) | 52 (35%) | 118 (40%) |
| Race | |||
| White | 95 (64%) | 103 (69%) | 198 (67%) |
| Black or African American | 20 (14%) | 16 (11%) | 36 (12%) |
| Native Hawaiian/other Pacific Islander | 0 | 1 (1%) | 1 (0.3%) |
| Asian | 5 (3%) | 3 (2%) | 8 (3%) |
| American Indian or Alaska Native | 1 (1%) | 0 | 1 (0.3%) |
| Multiple races | 3 (2%) | 3 (2%) | 6 (2%) |
| Unknown | 24 (16%) | 23 (15%) | 47 16%) |
| Histology, n(%) | |||
| Alveolar | 38 (26%) | 42 (28%) | 80 (27%) |
| Embryonal | 98 (66%) | 92 (62%) | 190 (64%) |
| Spindle Cell | 9 (6%) | 7 (5%) | 16 (5%) |
| Other | 3 (2%) | 8 (5%) | 11 (4%) |
| Primary site, n (%) | |||
| Orbit | 4 (3%) | 0 (0%) | 4 (1%) |
| Head & Neck, nonPM | 19 (13%) | 26 (17%) | 45 (15%) |
| PM | 36 (24%) | 41 (28%) | 77 (26%) |
| GU Non-Bladder | 6 (4%) | 6 (4%) | 12 (4%) |
| GU Bladder | 19 (13%) | 15 (10%) | 34 (11%) |
| Extremity | 20 (14%) | 22 (15%) | 42 (14%) |
| Intrathoracic | 3 (2%) | 3 (2%) | 6 (2%) |
| Perineum-Anus | 0 (0%) | 2 (1%) | 2 (1%) |
| Retroperineum | 22 (15%) | 15 (10%) | 37 (13%) |
| Trunk | 5 (3%) | 8 (5%) | 13 (4%) |
| Other | 14 (10%) | 11 (7%) | 25 (8%) |
| Group, n (%) | |||
| I | 5 (3%) | 6 (4%) | 11 (4%) |
| II | 11 (7%) | 7 (5%) | 18 (6%) |
| III | 117 (79%) | 118 (79%) | 235 (79%) |
| IV | 15 (10%) | 18 (12%) | 33 (11%) |
| Fusion, n (%) | |||
| FOX01- | 113 (77%) | 108 (73%) | 221 (75%) |
| PAX3 | 27 (18%) | 28 (19%) | 55 (19%) |
| PAX7 | 4 (3%) | 7 (5%) | 11 (4%) |
| PAX Other * | 3 (2%) | 5 (3%) | 8 (3%) |
| Missing | 1 | 1 | 2 |
| DPE, n (%) | 32 (100%) | 41 (100%) | 73 (100%) |
PAX Other includes FOX01+ and PAX Other or PAX Unknown
At a median follow-up of 3.57 years (IQR 2.80 to 4.51 years), there was no statistically significant difference in EFS between Arm A and Arm B (3-year EFS was 64.8% (95% CI: (55.5%, 74.1%)) vs. 66.8% (95% CI: (57.5%, 76.2%)), log-rank p=0.44). (Figure 2A) The hazard ratio of Arm B vs Arm A is 0.86 (95% CI: (0.58, 1.26)). The 3-year overall survival was 78.7% (95% CI: (70.9%, 86.4%)) vs. 77.8% (95% CI:(69.7%, 85.9%)) in Arms A and B, respectively (log-rank p=0.56). (Figure 2B) The hazard ratio of Arm B vs Arm A is 1.15 (95% CI: (0.72, 1.84)). One-sided p value<0.05 was considered significant. Sensitivity analysis was conducted. All randomized patients (N=310) were analyzed and compared by their assigned treatment group. Similar results were found. There was no statistically significant difference in EFS between arm A and Arm B (3-year EFS was 64.6% (95% CI: (55.7%, 73.6%)) vs. 66.3% (95% CI: (57.1%, 75.5%)), log-rank p=0.45). For EFS, there were 54 events (4 deaths and 50 Relapse/Progression) in Arm A and 50 events (4 deaths and 46 Relapse/progression) for Arm B. Of the total of 96 patients who experienced progressive disease/relapse, 62 (64.6%), 6 (6.2%), and 59 (61.4%) had local, regional or distant failures, respectively. For OS, there were 33 deaths in Arm A and 38 deaths in Arm B for a total of 71 deaths. Protocol therapy was the exclusive cause of 1 death (Arm B) and 63 deaths were deemed not related to the treatment: 3 (4.2%) due to ‘other cause’ (2 in Arm A, 1 Arm B), 60 (84.5%) due to the disease. (28 in ARM A, 32 in ARM B), 7 (9.9%) patients died for unknown reason (incomplete death form (2 on Arm A, 5 on Arm B)).
Figure 2A.
Event-Free Survival of Patients on Arm A and Arm B
Figure 2B.
Overall Survival of Patients on Arm A and Arm B
Post-hoc subgroup analyses did not demonstrate any impact of age, or FOXO1 translocation status (in non-metastatic patients,) favoring one arm over the other, although the study was not powered to confirm these observations.
EFS by specific sub-group is listed in Table 3.
Table 3.
Event-Free Survival by Translocation Status and Age
| 3 Year EFS Arm A | 3 Year EFS Arm B | EFS Difference (Arm B – Arm A) 90% Confidence Interval | |
|---|---|---|---|
|
FOXO1+/PAX7
Arm A=4 Arm B=7 |
66.8% | 65.8% | −1.0% (−14.2%,12.2%)* |
|
| |||
|
FOXO1+/PAX3
Arm A=20 Arm B=26 |
59.0% | 60.1% | 1.1% (−22.9%,25.0%) |
|
| |||
|
FOX01+ Other
Arm A=3 Arm B=5 |
37.5% | 100% | 62.5% (13.9%, 100%)* |
|
| |||
|
FOX01- Arm A=94 Arm B=84 |
50% | 80% | 30.0% (−37.2%, 97.2%) |
|
| |||
|
| |||
|
Age 0–9 years
Arm A=98 Arm B=99 |
67.1% | 71.1% | 4.0% (−9.0%, 17.0%) |
|
| |||
|
Age 10–17 years
Arm A=38 Arm B=29 |
63.8% | 61.3% | −2.5% (−28.1%, 23.2%) |
| Age 18+ years Arm A=12 Arm B=21 | 46.9% | 55. 6% | 8.7% (−25.9%, 43.2%) |
CI may not be accurate due to small sample size
Data on subsequent anti-cancer therapy following relapse/progression is not available.
All patients experienced at least one adverse event, most commonly neutropenia (100% of patients in both arms). All Grade 3 or higher events occurred more frequently in Arm B except anorexia and nausea (Table 2A). The total number of dose modifications and TEM doses given are shown in Table 2B. A total of 73 patients underwent DPE (32 Arm A, 41 Arm B). Very few patients experienced wound dehiscence (1 Arm A, 2 Arm B). The interval between courses among patients in Arm A vs. Arm B is listed. (Table 2B)
Table 2A.
Summary of Adverse Events*
| Arm A (N=148) | Arm B (N=149) | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Grade 1–2 | Grade 3 | Grade 4 | Grade 1–2 | Grade 3 | Grade 4 | |||||||
| N | N | N | N | N | N | |||||||
| ALT increased | 16 | 10.8% | 7 | 4.7% | 0 | 0.0% | 26 | 17.4% | 21 | 14.1% | 2 | 1.3% |
| Anemia | 96 | 64.9% | 60 | 40.5% | 2 | 1.4% | 103 | 69.1% | 86 | 57.7% | 3 | 2.0% |
| Anorexia | 25 | 16.9% | 26 | 17.6% | 0 | 0.0% | 26 | 17.4% | 20 | 13.4% | 0 | 0.0% |
| Diarrhea | 30 | 20.3% | 14 | 9.5% | 1 | 0.7% | 40 | 26.8% | 27 | 18.1% | 0 | 0.0% |
| Lymphopenia | 59 | 39.9% | 58 | 39.2% | 25 | 16.9% | 48 | 32.2% | 62 | 41.6% | 37 | 24.8% |
| Mucositis oral | 17 | 11.5% | 17 | 11.5% | 1 | 0.7% | 47 | 31.5% | 41 | 27.5% | 1 | 0.7% |
| Nausea | 44 | 29.7% | 19 | 12.8% | 0 | 0.0% | 46 | 30.9% | 14 | 9.4% | 0 | 0.0% |
| Neutropenia | 47 | 31.8% | 77 | 52.0% | 83 | 56.1% | 52 | 34.9% | 73 | 49.0% | 91 | 61.1% |
| Thrombocytopenia | 20 | 13.5% | 26 | 17.6% | 16 | 10.8% | 34 | 22.8% | 32 | 21.5% | 20 | 13.4% |
| Leukopenia | 73 | 49.3% | 79 | 53.4% | 42 | 28.4% | 73 | 49.0% | 84 | 56.4% | 48 | 32.2% |
Shows grade 1–2 events that occurred in at least 10% of patients, and all grade 3 and 4 events. There was one death in Arm A as ‘NOS’.
Table 2B.
Cycle Length and Dose Modifications
| Cycle 1 | Cycle 2 | Cycle 3 | Cycle 4 | Cycle 5–10 | Cycle 11–14 | |||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Arm A | Arm B | Arm A | Arm B | Arm A | Arm B | Arm A | Arm B | Arm A | Arm B | Arm A | Arm B | |
| 147 | 147 | 140 | 142 | 138 | 137 | 133 | 132 | 128 | 126 | 112 | 114 | |
| Total number of doses of TEM Median (Range) * | - | 2 (1–3) | - | 3 (2–3) | - | 3 (1–3) | - | 3 (0–3) | - | 8 (0–15) | - | 12 (0–16) |
| Cycle Length mean (median) days | 21.6 (21) | 28.1 (21) | 22.1 (21) | 22.4 (21) | 23.1 (21) | 24 (21) | 24 (21) | 25.7 (21) | 124.6 (128) |
129.8 (132) |
89.6 (87) | 90.1 (86.5) |
| Total number of events ** | ||||||||||||
| Reduction in Vincristine | 5 | 3 | 11 | 4 | 10 | 10 | 6 | 21 | 10 | 28 | 8 | 22 |
| Reduction in Dactinomycin | 0 | 1 | 1 | 1 | 2 | 3 | 1 | 0 | 3 | 8 | 1 | 4 |
| Reduction in Cyclophosphamide | 0 | 0 | 1 | 1 | 2 | 3 | 0 | 0 | 2 | 1 | 2 | 5 |
| Reduction in Irinotecan | 0 | 0 | 0 | 1 | 1 | 3 | 6 | 1 | 5 | 7 | 4 | 2 |
Represents the total number of doses of TEM given per cycle or cycle range
Represents the total number of patients had a dose reduction in a drug per cycle or cycle range
One hundred and one patients withdrew from treatment prior to completion of protocol therapy (including maintenance). (Figure 1)
Discussion
To date, to our knowledge, this is the largest international phase 3 randomized study conducted in RMS using FOXO1 fusion status for upfront patient stratification. This trial failed to show benefit of TEM added to standard VAC/VI chemotherapy compared with VAC/VI chemotherapy alone in patients with IR RMS. The FOXO1 gene belongs to the forkhead box family of transcription factors which plays a role in myogenic growth and differentiation. Translocation of the FOXO1 gene with PAX3, or less commonly PAX7, has usually been reflective of alveolar-type RMS. FOXO1 status predicted survival in patients with RMS beyond that of histological determination, especially between alveolar and embryonal histologies. (13, 14)
One explanation for the negative result seen in this study could be the increasingly apparent heterogeneity in the biological determinants of IR RMS. The proportion of patients in ARST0921 with alveolar RMS was 61% (6) compared with 27% (80 of 297) in our study and 46% in the prior intermediate risk study (ARST0531). (10) It is possible that the lack of benefit of TEM seen in our study was marred by the low proportion of patients with alveolar disease. Mammalian target of rapamycin (mTOR) participates in multiple signaling pathways and is composed of 2 protein complexes, mTOR complex 1 (mTORC1) and mTOR complex 2 (mTORC2) aptly co-named Raptor (regulatory-associated protein of mTOR) and Rictor (rapamycin-insensitive companion of mTOR), respectively. (15) The relative contribution of derangements in the mTOR pathway have been explored in RMS in many ways. For example, in a cohort of pediatric RMS samples (alveolar and embryonal), upregulation of mTOR either with high levels of Akt, 4EBP1, eIF4G, and/or p70S6 was associated with inferior event-free survival (16) and rapamycin treatment inhibited human RMS growth in xenograft mouse models.(17) However, RAS signalling abnormalities present especially in FOXO1 negative embryonal RMS may enable resistance to single inhibitors of the mTOR pathway (18) yielding more favorable inhibition with dual inhibitors to mTOR and RAS.(19) Although mTORC1 inhibitors initially exhibited some inhibitory effects, the tumors became resistant due to feedback activation of AKT signaling by the mTORC2-regulated phosphorylation (17) necessitating the use of inhibitors that could simultaneously target both mTORC1 and mTORC2 signaling pathways (18, 19). These inhibitors have been shown to be more effective than rapalogs such as TEM in suppressing protein synthesis and tumor growth.(20) Our choice of using TEM in this study was couched with pragmatism required in the design of phase 3 studies using novel drugs in ultra-rare pediatric cancers. These requirements include completed phase 1 pediatric data, combination safety data with chemotherapy, FDA approval (for other indications confirming its ongoing development) and the absence of overlapping toxicities with chemotherapy.
The practical issues surrounding the conduct of randomized controlled trials in rare pediatric cancers are the source of the major limitations of the study. We lack the power to examine specific effects of TEM on the subpopulations mentioned above. We did not have the capacity to perform central radiology review, and despite multiple attempts to clarify, there remained a substantial number of patients who did complete protocol therapy due to physician discretion or patient preference. It is unclear whether these patients stopped therapy specifically due to toxicity or other reasons.
We chose to use a backbone of VAC/VI in this study similar to that which was used in ARST0531. (10) However, due to the favorable results published in improvement of overall survival with the addition of maintenance chemotherapy by EpSSG, (21) we proceeded to also add maintenance therapy to our study. At this time, the overall impact of the addition of maintenance therapy to VAC/VI remains unclear. There is also emerging contemporary data confirming heterogeneity among the patients who are FOXO1 negative including those that carry mutations in MYOD1 (L122R) and p53 conferring exceptionally poor prognoses. (22, 23) PIK3CA mutations or PTEN deletions are commonly found in tumour samples harbouring the MYOD1 mutation and may suggest the relative importance of mTOR inhibitors in this particular sub-population (24, 25) in comparison whole populations of FOXO1 negative and positive cohorts wherein PIK3CA mutations are only detected in 8% and 3%, respectively. (22) Moreover, the presence of mTOR pathway involvement in RMS has been explored; in one study pAKT and pERK positivity was noted in 36% and 46% of alveolar and embryonal tissue microarray samples, respectively. (19) We have collected diagnostic tissue from all patients in the study and will be analyzing both via hybrid capture sequencing and low coverage whole-genome sequencing. These analyses will help us determine prevalence of mutations in PIK3CA and other genes involved in mTOR pathway regulation. International cooperative groups are motivated to incorporate these newly defined mutational subgroups in the design of future RMS trials and might need to consider asking treatment questions based on these ultra-rare sub-groups of patients. (26)
In addition to molecular or histological characterization, the clinical features defining RMS classified as ‘intermediate risk’ have continued to evolve over sequential COG studies. One group included in this study is those who are under the age of 10 years with embryonal histology, who are FOXO1 negative, but with distant metastases. This group of patients has toggled between inclusion in high versus intermediate-risk studies within the COG and has been recently considered in high-risk studies through the European paediatric Soft tissue sarcoma Study Group, EpSSG. These metastatic patients were included in the current study but not in the prior IR RMS study, ARST0531.(10) The second group are those with unresected tumours at a ‘favorable site’ dominated by females with RMS of the genital tract. Biologically, they are most often favorable biology - embryonal RMS - however, due to inadequate local control have had high rates of local failure. (27) These patients were thus promoted from low to IR risk due to their poor outcomes when receiving less intensive, low-risk chemotherapy. With these caveats, the overall EFS in this trial was comparable to that published for ARST0531 (4-year EFS of 59% (95% CI, 51% to 66%)) using the same VAC/VI backbone regimen and total number of patients who discontinued therapy is also similar (data not shown). (10)
In this trial, combining TEM with VAC/VI chemotherapy was safe. (3) The expected class toxicity of mucositis was high in those who received TEM, however, gastrointestinal toxicities was also noted in those who received abdominal RT. Further analysis on the scope of gastrointestinal toxicities associated with TEM plus RT is underway. There were dose reductions of the VAC/VI therapy in Arm B, an important consideration in a curative patient population.
In summary, to our knowledge, this is the largest prospective international study conducted in RMS to date using FOXO1 fusion determination for eligibility and molecular stratification. We will continue to interrogate specific molecular and histological subtypes within our study in order to further refine our understanding of this complex disease.
Research in Context
Evidence Before this study
The Children’s Oncology Group (COG) is largest pediatric oncology cooperative group running international trials in rhabdomyosarcoma alongside the European paediatric Soft tissue sarcoma Study Group, EpSSG. We searched PubMed using the search terms “rhabdomyosarcoma”, “clinical trials”, “temsirolimus” and “mTOR inhibitor” for studies published between Jan 1, 2010, and Dec 31, 2023, without language restrictions. We know that no prior phase 3 studies examining the role of an mTOR inhibitor in event-free survival of patients with intermediate risk rhabdomyosarcoma have been conducted. The COG completed a randomized phase 2 study examining the role of temsirolimus in first relapse RMS. In this study, those receiving chemotherapy with temsirolimus had superior event-free survival compared to those receiving chemotherapy plus bevacizumab. Moreover, FOXO1 fusion status is superior to histology (ie. alveolar vs. embryonal) in predicting biological behaviour and outcome of patients with rhabdomyosarcoma.
Added Value of this Study
Although the current study did not meet its statistical endpoint, this is the first ever study to report safety of combining temsirolimus with VAC/VI chemotherapy. Moreover, this is the first and largest study in pediatric rhabdomyosarcoma to stratify patients by the presence or absence of FOXO1 fusion, rather than histology alone.
Implications of all the available evidence
Temsirolimus did show significant benefit in improving EFS in newly diagnosed patients with intermediate risk rhabdomyosarcoma. Novel strategies are required to improve outcome in these patients.
Supplementary Material
Acknowledgements:
Research reported in this manuscript was supported by the Children’s Oncology Group, the National Cancer Institute of the National Institutes of Health under award number NCTN Operations Center Grant U10CA180886, NCTN Statistics & Data Center Grant U10CA180899 and St. Baldrick’s Foundation.
Footnotes
Declaration of interests
The authors declare no conflicts of interest.
Disclaimer:
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Contributor Information
Abha A. Gupta, Hospital for Sick Children, University of Toronto, Canada; Princess Margaret Cancer Center, University of Toronto, Canada.
Wei Xue, COG Data Center, Gainesville, FL.
Douglas J. Harrison, The University of Texas MD Anderson Cancer Center.
Douglas S. Hawkins, Seattle Children’s Hospital and University of Washington Medical Center, Seattle, WA.
Roshni Dasgupta, Cincinnati Childrens Hospital Medical Center, Cincinnati OH.
Suzanne Wolden, Memorial Sloan Kettering, New York City, NY.
Barry Shulkin, St. Jude Children’s Research Hospital, Memphis, TN.
Amira Qumseya, COG Data Center, Gainesville, FL.
Jonathan C. Routh, Duke University School of Medicine, Durham, NC.
Tamara MacDonald, IWK Health Center, Halifax, NS, Canada.
Shari Feinberg, Maimonides Cancer Center at Maimonides Medical Center and Children’s Hospital, Brooklyn, NY.
Brian Crompton, Dana-Farber/Boston Children’s Cancer and Blood Disorders Center, Boston, MA; Broad Institute.
Erin R. Rudzinski, Seattle Children’s Hospital and University of Washington Medical Center, Seattle, WA.
Michael Arnold, Children’s Hospital of Colorado, Aurora, CO.
Raj Venkatramani, Texas Children’s Cancer Center, Baylor College of Medicine, Houston, TX.
Data Sharing
An individual level de-identified dataset containing the variables analysed in the primary results paper can be expected to be available upon request. Requests for access to Children’s Oncology Group (COG) protocol research data should be sent to datarequest@childrensoncologygroup.org. Data are available to researchers whose proposed analysis is found by COG to be feasible and of scientific merit and who agree to the terms and conditions of use. In addition, release of data collected in a clinical trial conducted under a binding collaborative agreement between COG or the National Cancer Institute Cancer Therapy Evaluation Program and a pharmaceutical or biotechnology company must comply with the data sharing terms of the binding collaborative and contractual agreement and must receive the proper approvals.
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Associated Data
This section collects any data citations, data availability statements, or supplementary materials included in this article.
Supplementary Materials
Data Availability Statement
An individual level de-identified dataset containing the variables analysed in the primary results paper can be expected to be available upon request. Requests for access to Children’s Oncology Group (COG) protocol research data should be sent to datarequest@childrensoncologygroup.org. Data are available to researchers whose proposed analysis is found by COG to be feasible and of scientific merit and who agree to the terms and conditions of use. In addition, release of data collected in a clinical trial conducted under a binding collaborative agreement between COG or the National Cancer Institute Cancer Therapy Evaluation Program and a pharmaceutical or biotechnology company must comply with the data sharing terms of the binding collaborative and contractual agreement and must receive the proper approvals.