Abstract
Objective
The purpose was to compare local control (LC), overall survival (OS) and dose to the organs at risk (OAR) in women with locally advanced cervical cancer treated with MR-guided versus CT-guided interstitial brachytherapy (BT).
Methods
56 patients (29 MR, 27 CT) were treated with high-dose-rate (HDR) interstitial BT between 2005–2015. The MR patients had been prospectively enrolled on a Phase II clinical trial. Data were analyzed using Kaplan-Meier (K-M) and Cox proportional hazards statistical modeling in JMP® & R®.
Results
Median follow-up time was 19.7 months (MR group) and 18.4 months (CT group). There were no statistically significant differences in patient age at diagnosis, histology, percent with tumor size >4 cm, grade, FIGO stage or lymph node involvement between the groups. Patients in the MR group had more lymphovascular involvement compared to patients in the CT group (p<0.01). When evaluating plans generated, there were no statistically significant differences in median cumulative dose to the high-risk clinical target volume or the OAR.
2-year K-M LC rates for MR-based and CT-based treatments were 96% and 87%, respectively (log-rank p=0.65). At 2 years, OS was significantly better in the MR-guided cohort (84% vs. 56%, p=0.036). On multivariate analysis, squamous histology was associated with longer OS (HR 0.23, 95% CI 0.07–0.72) in a model with MR BT (HR 0.35, 95% CI 0.08–1.18).
Conclusion
In this population of locally advanced cervical-cancer patients, MR-guided HDR BT resulted in estimated 96% 2-year local control and excellent early survival rates. Squamous cell histology was the most significant predictor for survival.
Keywords: Cervical carcinoma, Interstitial brachytherapy, MR-guidance, Radiation Oncology
INTRODUCTION
Treatment for locally advanced cervical cancer typically involves a combination of concurrent chemoradiation followed by brachytherapy (BT)[1]. BT is a major component of this treatment regimen; the modality has evolved from 2D-based dosimetry using point-based dosing to 3D-based volumetric planning. Volumetric planning can increase the precision of radiation dose delivery by improving the tumor definition and adjacent normal structures, resulting in coverage of the target and sparing of normal tissues. A prospective trial evaluating the efficacy of 3D-based volumetric planning found that 3D BT was associated with improved local relapse-free survival at 24 months compared to 2D imaging (78.5% vs. 73.9%) and with 20% lower global grade 3–4 toxicity (2.6% vs. 22.7%) in patients who received external beam radiation therapy (EBRT) and chemotherapy followed by BT [2].
Technological advances in BT planning include the introduction of magnetic resonance (MR)-guided treatment. MRI allows for assessment of tissue heterogeneity, as well as measurement of the extent of local tumor invasion of the parametria, vagina, uterus, bladder, and rectum. MR imaging arguably permits better visualization of the tumor at the time of BT, thereby allowing better dose distribution that should lead to improved outcomes. MR-based brachytherapy includes MR imaging obtained after the implant is complete, whereas MR guidance allows real-time imaging with adjustment of the catheters during the insertion process. The promise of 3D imaging to aid in tumor delineation led to the publication of MR based post-implant imaging and contouring guidelines by the GEC-ESTRO (Groupe Europeen de Curietherapie and the European Society for Radiotherapy and Oncology) [3]. Recently, the results from a retroprospective analysis from multiple institutions using 3D imaging after brachytherapy applicator insertion showed that among 731 patients with 43 months of follow-up, 3-year OS, pelvic control, local control (LC), and cancer-specific survival was 74%, 87%, 91%, and 79% respectively [4]. In a prospective trial of MR-guided brachytherapy (EMBRACE, international study on MRI-guided Brachytherapy in Locally Advanced Cervical Cancer) 23% of patients received a combined intracavitary/interstitial approach for at least one BT fraction. A follow-up analysis of rectal toxicities showed that the 3-year fistula risk was 12.5% with D2cc ≥ 75 Gy, and patients had a two-fold lower risk of proctitis with D2cc <65 Gy [5].
Patients with large tumors that may benefit the most from MR guidance [6]. We enrolled patients with locally advanced cervical cancer on a prospective clinical trial of MR based brachytherapy (clinicaltrial.gov identified NCT01399658) and compared these to CT based brachytherapy, with the goal of analyzing clinical outcomes as well as evaluating the toxicity profile of each method to determine if there is an advantage using one imaging modality versus the other.
MATERIALS AND METHODS
Patients
Records of 56 patients with biopsy-proven locally advanced cervical cancer who were treated with HDR interstitial BT between 2005 and 2015 were reviewed under an Institutional Review Board-approved protocol. Twenty-nine patients (52%) received 3D MR-guided interstitial catheter placement in a dedicated multimodality operating suite; all 29 were enrolled in a Phase II clinical trial and the treatment and outcome records from that trial were used for this study. The other 27 patients received 3D CT-based treatment planning. The medical records of those CT-based patients were identified and reviewed for patient, tumor, and treatment characteristics and clinical outcomes. Characteristics recorded included date of diagnosis, age at diagnosis, tumor size, grade, histology, International Federation of Gynecology and Obstetrics (FIGO) primary disease stage, and presence of lymphovascular invasion (LVI). Locally advanced disease was defined as stage IB2-IVA.
Treatment Procedures and Data Collection
All patients were treated with EBRT followed by HDR interstitial BT. HDR was administered twice daily, and the cumulative radiation dose was converted to biological equivalent dose (BED) in 2-Gy fractions using the quadratic BED equation with an α/β ratio of 10 for the contoured high-risk clinical tumor volume (HR-CTV), and an α/β ratio of 3 for normal tissues and organs at risk (OAR).
Details of insertion technique and treatment planning have been described previously [7–9]. Most patients treated with template-based interstitial implants received both epidural anesthesia and general anesthesia, which was initiated on entering the MR or CT unit. Epidural anesthesia continued over the duration of the inpatient hospitalization (approximately 3 days). For patients with an intact uterus, a CT-/MR-compatible tandem was placed using ultrasound-guidance. The central obturator (Best Medical International, Springfield, VA) was placed over the distal end of the tandem and advanced the full length of the vaginal canal. A Syed disposable template (Best Medical International, Springfield, VA) was placed over the obturator and sutured to the perineum. Catheters (Pro Guide, Elekta, Stockholm, Sweden) were iteratively inserted with image guidance under physician direction to maximize tumor coverage. Other patients had a ring or ovoids placed with interstitial catheters inserted through preset holes in the applicator. CT imaging (GE CT, 2-mm slices, 120 kVp, 300 mA, 60-cm field of view) or 3T MR (Siemens Verio) T2-weighted fast spin echo (Siemens turbo spin echo or TSE and fat-suppressed 3D gradient echo, Siemens VIBE) as well as RF-spoiled gradient echo (GRE) sequences were performed. Treatment planning (Oncentra workstation, Elekta) calculated the D90 to the clinical target (CTV) and the D2cc doses to the organs at risk. Other treatment data collected included EBRT technique, number of fractions and dosing; number of HDR fractions; BT dosing; history of previous radiation treatment; and concurrent chemotherapy use, including chemotherapy agents used.
Clinical Endpoints
Patients were followed for outcomes including LC, disease-free interval (DFI) and OS, as well as post-treatment toxicities. In the MR-cohort, patients were seen in follow-up 90 days post-treatment and underwent a pelvic MRI +/− a PET/CT as well as 180 days post-treatment. Follow-up time was capped at 6 months for the MR-ISBT patients treated after November 11, 2014. In the CT-cohort, patients underwent a PET/CT at 90 days, with no further imaging if a complete response was achieved. Patients were examined every 3 months for 2 years. Local recurrence (LR) was defined as biopsy-proven disease or clinical progression in the true or central pelvis (cervix and adjacent tissues). Regional recurrence was defined as relapse in the pelvic nodes or pelvic sidewalls, and distant metastases as recurrent disease outside the pelvis. Treatment-related complications were evaluated according to the Common Toxicity Criteria for Adverse Events (v. 4) [10].
Statistical Analysis
For numeric variables, we reported median with interquartile range or mean with standard deviation, and percentages for categorical and ordinal variables. To compare the two treatment groups, Chi-square analyses were used; Fisher’s exact test was used for binary variables when sample sizes were small. The likelihood ratio test was used for categorical variables with multiple groups. The Kaplan-Meier method was used to generate actuarial survival estimates and plots; these were compared using the log rank test. Univariate and multivariate Cox proportional hazards models created by backward selection methods were used to identify predictors of LC, DFI, and OS. All statistical analyses were performed using JMP version 13.0 (SAS Institute Cary, NC) and R version 3.3.2 [11]. Statistical tests were two-sided and considered significant for p-values less than 0.05.
RESULTS
Patients
Fifty-six patients fit the inclusion criteria for this study and were included in the analysis. Twenty-nine patients (52%) received MR-guided interstitial catheter placement, and 27 (48%) received CT-based planning and treatment. The two study groups were well balanced with respect to baseline characteristics (Table 1). All patients in the MR-guided group had received concomitant chemotherapy with the EBRT (87% cisplatin) compared to 26/27 in the CT-guided group (76% cisplatin; p=NS). Median follow-up time was 18.6 months (rg, 1.2–92.8) overall and was 18.4 (rg, 5.5–92.8) months for the CT cohort and 19.7 (rg, 1.2–59.5) months for the MR cohort (p=0.44).
Table 1.
Patient, Tumor and Treatment Characteristics
| Category | All Patients (N = 56) | CT-guided ISBT (n = 27) | MR-guided ISBT (n = 29) | P-value |
|---|---|---|---|---|
| Median follow-up (months) | 18.6 (1.2–92.8) | 18.4 (5.5–92.8) | 19.7 (1.2–59.5) | 0.28 |
| Median age at diagnosis (years) | 55.0 (26.9–77.5) | 57.6 (26.9–77.5) | 49.9 (29.0–77.0) | 0.11 |
| ECOG status | ||||
| >2 | 2 (3%) | 0 (0%) | 2 (7%) | 0.11 |
| ≤2 | 52 (94%) | 25 (93%) | 27 (93%) | |
| Not defined | 2 (3%) | 2 (7%) | 0 (0%) | |
| Year of diagnosis | ||||
| 2005 – 2010 | 11 (20%) | 11 (41%) | 0 (0%) | <0.01 |
| 2011 – 2015 | 45 (80%) | 16 (59%) | 29 (100%) | |
| Diagnostic Method | ||||
| MRI | 47 (84%) | 20 (74%) | 27 (93%) | 0.04 |
| PET/CT | 55 (98%) | 27 (100%) | 28 (97%) | 0.25 |
| Tumor size (continuous) cm | 5.6 (0.5–10) | 5.3 (2.0–9.1) | 5.8 (0.5–10) | 0.62 |
| ≤4 cm | 16 (28%) | 8 (30%) | 8 (28%) | 0.93 |
| > 4 cm | 39 (70%) | 19 (70%) | 20 (70%) | |
| Not identified | 1 (2%) | 0 (0%) | 1 (2%) | |
| Primary disease stage (FIGO) | ||||
| I | 3 (5%) | 2 (7%) | 1 (3%) | 0.37 |
| II | 11 (20%) | 7 (27%) | 4 (14%) | |
| III | 25 (45%) | 9 (33%) | 16 (55%) | |
| IVA | 17 (30%) | 9 (33%) | 8 (28%) | |
| Histology | ||||
| Squamous cell | 48 (86%) | 21 (77%) | 27 (93%) | 0.25 |
| Adenocarcinoma | 6 (11%) | 4 (15%) | 2 (7%) | |
| Others* | 2 (3%) | 2 (8%) | 0 (0%) | |
| Grade | ||||
| 1 | 4 (7%) | 2 (7%) | 2 (7%) | 0.54 |
| 2 | 21 (38%) | 8 (30%) | 13 (45%) | |
| 3 | 29 (52%) | 16 (60%) | 13 (45%) | |
| Not defined | 2 (3%) | 1 (3%) | 1 (3%) | |
| LVI present | 29 (52%) | 9 (33%) | 20 (69%) | <0.01 |
| Lymph node involved | 37 (66%) | 18 (67%) | 19 (66%) | 0.93 |
| Chemotherapy use (yes) | 55 (98%) | 26 (96%) | 29 (100%) | 0.25 |
| Cisplatin | 45 (80%) | 20 (76%) | 25 (87%) | |
| Carboplatin | 4 (8%) | 2 (8%) | 2 (7%) | |
| Cisplatin / Taxol | 1 (2%) | 1 (4%) | 0 (0%) | |
| Carboplatin / Taxol | 1 (2%) | 0 (0%) | 1 (3%) | |
| Cisplatin / Gemcitabine | 1 (2%) | 1 (4%) | 0 (0%) | |
| Not identified / None | 3 (6%) | 2 (8%) | 1 (3%) | |
| Radiation therapy | ||||
| EBRT (Yes) | ||||
| Techniques | ||||
| IMRT | 16 (29%) | 7 (26%) | 9 (31%) | |
| 4-field | 25 (45%) | 12 (44%) | 13 (45%) | |
| AP/PA | 1 (2%) | 0 (0%) | 1 (3%) | |
| Others** | 4 (6%) | 2 (7%) | 2 (7%) | |
| Not defined | 10 (18%) | 6 (23%) | 4 (14%) | |
| Median dose (EQD2) - Gy | 45.0 (45.0–57.6) | 45.0 (45.0–57.6) | 45.0 (45.0–54.8) | 0.15 |
| Brachytherapy | ||||
| Brachytherapy Type | 0.01 | |||
| Interstitial # | 5 (10%) | 1 (4%) | 4 (14%) | |
| Tandem & Interstitial | 45 (80%) | 26 (96%) | 19 (66%) | |
| Tandem & Ring & Interstitial | 4 (7%) | 0 (0%) | 4 (14%) | |
| Tandem & Ovoid & Interstitial | 2 (3%) | 0 (0%) | 2 (6%) | |
| Median number of fractions | 5 (2–9) | 5 (2–9) | 5 (4–9) | 0.92 |
| Median dose per fraction Gy | 5.3 (3.0–9.0) | 5.5 (3.0–9.0) | 5.0 (3.0–6.0) | 0.17 |
| Median dose (EQD2) - Gy | ||||
| Prescription | 35.5 (21.1–45.1) | 35.4 (27.2–43.2) | 35.5 (21.1–45.1) | 0.45 |
| D90 | 32.9 (11.7–58.9) | 32.1 (11.7–58.9) | 33.5 (18.6–55.8) | 0.96 |
| D2CC rectum | 22.2 (5.0–44.5) | 23.5 (5.0–44.5) | 22.0 (10.4–38.3) | 0.33 |
| D2CC bladder | 32.6 (14.1–153.1) | 31.4 (14.1–89.3) | 35.6 (15.5–153.1) | 0.18 |
| D2CC sigmoid | 18.5 (0.0–41.3) | 15.3 (0.0–36.4) | 21.5 (3.1–41.3) | 0.33 |
| Cumulative Dose (EQD2) - Gy | ||||
| EBRT+BT | 80.6 (70.7–94.7) | 80.1 (77.1–94.7) | 80.3 (70.7–89.4) | 0.79 |
| D90 | 80.7 (57.9–100.2) | 81.2 (57.9–100.2) | 79.8 (62.8–100.0) | 0.51 |
| D2CC rectum | 70.1 (56.4–92.5) | 70.2 (56.4–92.5) | 69.3 (57.3–81.5) | 0.43 |
| D2CC bladder | 82.1 (58.7–196.3) | 81.8 (62.1–185.5) | 82.4 (58.7–196.3) | 0.80 |
| D2CC sigmoid | 66.0 (46.4–87.5) | 66.2 (46.4–87.5) | 65.6 (48.9–86.2) | 0.96 |
Histology: Adenosquamous, clear cell;
3-field, Modified Segmental Boost Technique (MSBT);
Prior supracervical hysterectomy (no tandem feasible)
Key: IMRT: Intensity Modulated Radiation Therapy; EBRT: External Beam Radiation Therapy; Brachy: Brachytherapy
Most patients presented with squamous cell histology (85%) and tumors >4 cm (70%; median, 5.6 cm; range, 0.5–10); these characteristics were not statistically different between the two cohorts. Most patients (94%) had an ECOG performance score ≤ 2. Sixty-six percent of patients had lymph node involvement at presentation; 5% had FIGO stage I disease, 20% stage II, 45% stage III, and 30% stage IV. In the MR-guided group, the majority of patients had moderately-differentiated tumors (45%) whereas 60% of patients in the CT-guided group had poorly-differentiated tumors; this difference was not statistically significant. There were no statistically significant differences in FIGO stage or lymph node involvement between the two groups (p=0.37 and p=0.93, respectively). In addition, there were no statistically significant differences in tumor grade (p=0.54) at time of diagnosis. Patients in the MR-guided group were more likely to have LVI (p<0.01). Compared to the CT cohort, patients treated with MR-based BT were younger (median age: MR=49.9 years, CT=57.6 years); this was not statistically significant (p=0.11). Patients in the MR-based BT group were more likely to have been diagnosed later in the time period reviewed (i.e., between 2011 and 2015 versus 2005–2010, p<0.01) and 20 patients in the CT group versus 27 patients in the MR group had MR imaging at diagnosis (p=0.04). In the CT cohort, all patients but one had tandem and interstitial BT (without ring or ovoids), while 66% of patients in the MR-based group had tandem and interstitial BT (p=0.01).
Dosimetric parameters
With regard to graphic plans generated at the time of BT, there were no statistically significant differences in median cumulative dose to the contoured HR-CTV for any of the following: 2-Gy (EQD2) fractions (MR=80.3 Gy, CT=80.1 Gy, p=0.79); D90 tumor (MR=79.8 Gy, CT=81.2 Gy, p=0.51); D2cc rectum (MR=69.3 Gy, CT=70.2 Gy, p=0.43); D2cc bladder (MR=82.4 Gy, CT=81.8 Gy, p=0.80); and D2cc sigmoid (MR=65.6 Gy, CT=66.2 Gy, p=0.96 (Table 1).
Local Recurrence and Overall Survival
At the time of analysis, there were 2 LRs in the MR-guided group and 3 in the CT-guided group, corresponding to 2-year LC rates of 96% and 87%, respectively (p=0.65) (Figure 1). Characteristics of patients with local and distant recurrences are listed in Table 2. Two-year DFI rates were 73% and 65% in the MR-guided versus CT-guided group, respectively (p=0.87) (Supplemental Figure S1). There were 3 deaths (10%) in the MR-guided group and 11 (41%) in the CT-guided group. All 3 deaths in the MR-guided cohort were due to disease progression. In the CT-guided cohort, 4 deaths (36%) were due to disease progression, 1 (9%) to infection/sepsis, and 6 (55%) were of unknown cause. Of the 6 with unknown cause, 1 had documented LR and 3 had documented distant metastases. Two-year Kaplan-Meier OS rates were 84% and 56% for the MR and CT groups, respectively (p=0.036) (Figure 2).
Figure 1.
Kaplan-Meier Plot of Local Control.
Local control by imaging modality utilized during brachytherapy. There were 2 local recurrences in the MR-guided BT group and 3 local recurrences in the CT-guided BT group, resulting in 2-year local control rates of 96% and 87%, respectively.
Table 2.
Patient, Tumor and Treatment Characteristics of All Recurrences
| Age at diag.(yrs) | Histo | Primary stage | Tumor grade | Tumor size (cm) | LVI | Site of recur. | Time to recur. (mos.) | BT dose (Gy) | Cum. EQD2 (Gy) | |
|---|---|---|---|---|---|---|---|---|---|---|
| MR-guided ISBT | 38 | SCC | IIB | 2 | 5.3 | Yes | Distant (peritoneum) | 7 | 34 | 84.92 |
| 59 | SCC | IIIB | 2 | 6 | No | Rectum/anus | 57 | 33.75 | 82.92 | |
| 49 | Adenoca | IVA | 3 | 8 | Yes | Distant (lung) | 26 | 30 | 81.75 | |
| 25 | SCC | IIB | 2 | 4.7 | No | Left SCV LN, RP LNs | 17 | 27.5 | 83.18 | |
| 58 | SCC | IIIB | 1 | 10 | Yes | Aortocaval LN | 4 | 27.5 | 79.77 | |
| 41 | SCC | IVA | 3 | 4 | Yes | Liver, spleen | 18 | 17.6 | 74.22 | |
| 33 | SCC | IIIB | 1 | 6 | Yes | Bone metastases | 6 | 29.75 | 82.98 | |
| 29 | SCC | IIIB | 2 | 7.3 | Yes | Parametrium | 5.5 | 27 | 82.19 | |
| 29 | SCC | IIIB | 3 | 7.8 | Yes | Pelvic LN | 1.5 | 31.5 | 82.19 | |
| CT-guided ISBT | 52 | SCC | IVA | 3 | 6.7 | No | Distant (lung) | 3 | 30 | 84.3 |
| 67 | SCC | IIIA | 3 | 3 | Yes | Cervix, PAN | 5 | 33.5 | 83.9 | |
| 60 | SCC | IVB | 2 | 7.6 | NI | Distant (lung) | 2 | 28 | 83.9 | |
| 60 | SCC | IIA | 2 | 2.9 | NI | Pelvic nodule, bladder | 14.5 | 27.5 | 79.8 | |
| 43 | SCC | IVA | 3 | 3.6 | Yes | Uterus, aortocaval LN | 5 | 27.5 | 79.8 | |
| 43 | SCC | IVB | NI | 7.8 | NI | Distant prog NOS | 4 | 31.5 | 79.4 | |
| 43 | Adenoca | IIB | 3 | 7.3 | NI | PAN, RP LNs | 5 | 27 | 77.9 | |
| 63 | SCC | IIIB | 2 | 7.4 | NI | Axillary LN | 27 | 31.5 | 79.7 | |
| 34 | Adenoca | IB2 | 3 | 7.3 | NI | PAN | 4 | 33.75 | 82.9 |
Key: ISBT, Interstitial brachytherapy; Histo, Histology; SCC, Squamous cell carcinoma; Adenoca, Adenocarcinoma; Adenosq, Adenosquamous; Recur, Recurrent; BT, Brachytherapy; abd, abdominal; LN, lymph node; PAN, Para-aortic node; NI, Not identified; prog, progression; SCV, Supraclavicular; NOS, not otherwise specified; italicized refers to local recurrence
Figure 2.
Kaplan-Meier Plot of Overall Survival.
Overall survival by imaging modality utilized during brachytherapy. MR-guided BT was associated with significantly longer overall survival compared to CT-guided BT.
On univariate analysis, no factors were found to be significantly associated with LC or DFI (Table 3a). For OS, squamous cell histology and MR-guided interstitial BT were associated with a significantly lower risk of death. On multivariate analysis, after adjusting for multiple factors, only squamous cell histology was associated with longer OS (HR 0.23, 95% CI 0.07–0.72, p=0.0134) (Table 3b).
Table 3a.
Univariate Cox Analysis
| Categoryǂ | LC (univariate) | DFI (univariate) | OS (univariate) | |||
|---|---|---|---|---|---|---|
| HR (95% CI) | p-value | HR (95% CI) | p-value | HR (95% CI) | p-value | |
| Age at diag. (continuous) | 1.02 (0.95–1.10) | 0.63 | 0.97 (0.94–1.01) | 0.19 | 1.01 (0.96–1.06) | 0.76 |
| Year of Diagnosis | ||||||
| ≤2010 | 2.18 (0.26–13.98) | 0.43 | 1.93 (0.66–5.06) | 0.22 | 1.97 (0.59–5.94) | 0.25 |
| >2010★ | 1 | 1 | 1 | |||
| Tumor size (cm) | ||||||
| Continuous | 1.07 (0.71–1.71) | 0.76 | 1.05 (0.84–1.34) | 0.65 | 1.05 (0.81–1.38) | 0.72 |
| FIGO stage (primary) | ||||||
| III–IV | 1.34 (0.20–26.23) | 0.79 | 0.92 (0.35–2.88) | 0.87 | 0.91 (0.30–3.35) | 0.87 |
| I – II★ | 1 | 1 | 1 | |||
| Grade | ||||||
| 3 | - | 0.25 | 0.89 (0.21–6.09) | 0.89 | - | 0.07 |
| 2 | - | 0.31 | 1.50 (0.38–10.02) | 0.59 | - | 0.07 |
| 1★ | 1 | 1 | 1 | |||
| Histology | ||||||
| SCC | 0.44 (0.06–8.91) | 0.51 | 0.60 (0.19–2.60) | 0.44 | 0.19 (0.06–0.58) | 0.005 |
| Others★ | 1 | 1 | 1 | |||
| Lymphovascular invasion | ||||||
| Yes | - | - | 1.83 (0.63–6.03) | 0.27 | 1.25 (0.39–4.36) | 0.71 |
| Lymph node involvement | ||||||
| Yes | 0.32 (0.04–1.93) | 0.21 | 1.66 (0.62–5.17) | 0.32 | 1.16 (0.38–3.86) | 0.79 |
| BT imaging status | ||||||
| MR-guided ISBT | 0.65 (0.08–4.13) | 0.64 | 0.92 (0.36–2.41) | 0.87 | 0.27 (0.06–0.90) | 0.03 |
| CT-guided ISBT★ | 1 | 1 | 1 | |||
| BT dose (EQD2) | 0.97 (0.81–1.18) | 0.73 | 1.02 (0.93–1.12) | 0.68 | 1.01 (0.91–1.13) | 0.86 |
| Cum. dose (EQD2) | 1.00 (0.79–1.23) | 0.97 | 0.97 (0.87–1.09) | 0.68 | 1.04 (0.91–1.17) | 0.58 |
| Cum. D90 (EQD2) | 1.03 (0.94–1.14) | 0.58 | 1.02 (0.97–1.08) | 0.44 | 1.01 (0.95–1.07) | 0.80 |
Referent group;
unknown values excluded from the analyses
Key: Diag, Diagnosis; BT, Brachytherapy; ISBT, Interstitial brachytherapy; Adenoca, Adenocarcinoma; Cum, Cumulative:
Table 3b.
Multivariable Cox Analysis
| OS (adjusted) | ||
|---|---|---|
| HR (95% CI) | p-value | |
| MR-guided ISBT | 0.35 (0.08–1.18) | 0.09 |
| Histology SCC | 0.23 (0.07–0.72) | 0.013 |
Key: SCC, Squamous cell carcinoma
Toxicities
There were no significant differences in toxicities comparing CT to MR. Rectal toxicity was noted in 8 patients in the MR-based cohort and 9 in the CT-based cohort. With respect to toxicity grade, there were 3 vs. 5 grade 1 toxicities (p=0.38), 4 vs. 1 grade 2 toxicities (p=0.17), and 3 vs. 4 grade 3 toxicities (p=0.61) in the MR- and CT-cohorts, respectively; there was no grade 4 rectal toxicity. Urinary toxicity was noted in 8 patients in the MR-based cohort and 6 in the CT-based cohort. Urinary toxicity grades were 6 vs. 4 grade 1 (p=0.57), 3 vs. 3 grade 2 (p=0.93), and 3 vs. 1 grade 3 (p=0.32) in the MR- and CT-cohorts, respectively; no grade 4 urinary toxicity was reported (Table 4).
Table 4.
Toxicities(assessed using the Common Toxicity Criteria Version 4.3)
| Characteristics | Grade | CT-guided ISBT (n =27) | MR-guided ISBT (n =29) | p-value |
|---|---|---|---|---|
| Rectal | 1 | 5 | 3 | 0.38 |
| 2 | 1 | 4 | 0.17 | |
| 3 | 4 | 3 | 0.61 | |
| Urinary | 1 | 4 | 6 | 0.57 |
| 2 | 3 | 3 | 0.93 | |
| 3 | 1 | 3 | 0.32 |
Key: ISBT, Interstitial brachytherapy
DISCUSSION
In this study we evaluated outcomes for women with locally advanced cervical cancer treated with either MR-guided brachytherapy or CT-guided BT. The two cohorts were otherwise treated the same way and had no major significant differences in their baseline tumor characteristics or dosimetry, except for the presence of LVI. We found no significant differences between the groups with respect to local recurrence or toxicity. On multivariate analysis, only squamous histology significantly predicted for improved OS with MR resulting in a 65% improvement in survival that was not statistically significant.
Brachytherapy is an essential curative element in the treatment of locally advanced cervical cancer. Advances in imaging and volumetric planning have achieved more precise radiation delivery with a defined outline of the tumor and organs at risk, thereby allowing an accurate estimate of dose delivered. MR-guided BT is arguably an improvement over CT-guided BT, due to the improved visualization of critical soft tissue planes, allowing assessment of local invasion.
MR-based BT guidelines were introduced in 2005 after publication of the GEC-ESTRO guidelines [12]. Our institution began a program of MR-guided interstitial BT in 2002; we prospectively enrolled 25 patients to a clinical trial with a 0.5T MR [8] and described the feasibility and low toxicity rate using MR-guided interstitial brachytherapy [13].
Interstitial BT is necessary for patients with bulky, locally advanced cervical carcinoma, given that LC rates with EBRT and intracavitary BT range from 48–63% for Stage III and 13–18% for Stage IV disease [14]. Syed et al. reported on the use of interstitial BT for locally advanced cancers in 87 patients with Stage III/IV disease, resulting in a 73% overall LC rate and a 5-year DFI of 58%. This study used orthogonal films and image reconstruction to determine dose to tumor and normal tissues. Our study found that MR-guided BT resulted in a higher 2-year LC rate compared to CT-guided BT (96% vs. 87%) that was not statistically significant likely due to the low number of local relapses. MR-guided planning was associated with a significantly improved OS as compared to CT-guided planning. We evaluated upfront characteristics between the two groups, including ECOG status, which was not significantly different between the two groups. Patients in the MR-cohort had a slightly larger median tumor size compared to patients in the CT-cohort (5.8 versus 5.3 cm, respectively) and had significantly more LVI. The MR-guided cohort was enrolled on a prospective trial, and had slightly longer follow up. Most patients relapse in the first two years, though longer follow up will help provide information about late relapses and how this may impact survival after 2 years. Squamous histology predicted for improved OS on multivariate analysis. This is consistent with previous reports noting that squamous cell histology is a positive prognostic factor for cervical cancer patients [15–16].
Complications from interstitial BT were common in the 2D era. In the aforementioned Syed et al. trial, 10% of the cohort had grade 3 or 4 toxicities and the fistula rate was 4% [14]. The introduction of CT-based guidance for interstitial planning purposes allowed for more accurate dosimetric planning and analysis [17]. The visualization of OARs allowed for better dosimetry, with easier distinction between tumor and normal tissues, thereby leading to lower complication rates [18]. Although rectal and genitourinary grade 1–3 toxicities were noted in both CT and MR groups, there were no grade 4 toxicities. Both CT and MR imaging modalities are excellent at delineating normal tissue if bladder and rectal contrast are used for the CT, therefore we did not expect a significant difference in OAR contouring between the two [19]. MR superiority is with regards to improved tumor visualization [6]. In future studies, if the treated region is limited to just the MR defined tumor volume rather than to the entire cervix, then we would hope for lower doses to the OARs and a difference in toxicity. By covering an HR-CTV in both, the area treated in CT and MR are similar enough that no toxicity difference was observed. Longer follow-up is needed to determine if late toxicities will differ between the MR and CT groups.
There are several limitations to the study that must be recognized. This is a small, single-institutional analysis, with the MR patients enrolled on a prospective trial. Patients on a prospective trial are subject to more rigorous follow-up. In the future, it would be beneficial to study this in a larger trial with longer follow-up. As MR utilization increases in the US and elsewhere, this is becoming feasible to consider. In a survey by the American Brachytherapy Society, the utilization of MRI increased from 2% to 34% between 2007 and 2014 [20]. Given that almost all centers in the United States have access to a CT scanner, 88% of respondents of the survey obtain a CT scan at the first applicator insertion, and 77% get a CT scan at the first and subsequent fractions. An MRI scan may provide crucial details about the tumor, and when obtained a few days before brachytherapy, can still provide important information; this is recommended when an MR immediately after implantation is not feasible.
In conclusion, we found that treatment of locally advanced cervical cancer with MR-guided interstitial BT following EBRT with concurrent chemotherapy was associated with equivalent local control, toxicity and improved overall survival when compared to CT-guided interstitial BT. Squamous histology was the most significant predictor for improved survival. As MR imaging is the gold standard for cervical cancer, more centers may be incorporating MR-guided interstitial BT due to its improved soft-tissue delineation. Future trials should incorporate MR-guided interstitial BT in the treatment of large volume locally advanced cervical cancer.
Supplementary Material
Kaplan-Meier Plot of Disease-Free Interval.
Disease-free interval by imaging modality utilized during brachytherapy. 2-year DFI rates were 72% and 65% in the MR-guided and CT-guided groups, respectively (p=0.87).
HIGHLIGHTS.
MR-guided interstitial brachytherapy results in a 96% local control rate.
There were no statistically significant dosimetric differences between modalities.
Histology was a significant predictor for survival.
Acknowledgments
Dr. Viswanathan and this research were funded by the National Cancer Institute (R21-167800).
Footnotes
Presented at American Brachytherapy Society World Congress of Brachytherapy, June 27–29, 2016, San Francisco, CA
Conflict of Interest Statement: The authors declare that they have no conflict of interest.
Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
References
- 1.Chemoradiotherapy for Cervical Cancer Meta-Analysis Collaboration. Reducing uncertainties about the effects of chemoradiotherapy for cervical cancer: A systemic review and meta-analysis of individual patient data from 18 randomized trials. J Clin Oncol. 2008;26(35):5802–12. doi: 10.1200/JCO.2008.16.4368. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 2.Charra-Brunaud C, Harter V, Delannes M, et al. Impact of 3D image-based PDR brachytherapy on outcome of patients treated cervix carcinoma in France: results of the French STIC prospective study. Radiother Oncol. 2012;103(3):305–13. doi: 10.1016/j.radonc.2012.04.007. [DOI] [PubMed] [Google Scholar]
- 3.Dimopoulos JCA, Petrow P, Tanderup K, et al. Recommendations from Gynaelogical (GYN) GEC-ESTRO working group (IV): Basic principles and parameters for MR imaging within the frame of image based adaptive cervix cancer brachytherapy. Radiother Oncol. 2012;103(1):113–22. doi: 10.1016/j.radonc.2011.12.024. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 4.Sturdza A, Potter R, Fokdal LU, et al. Image guided brachytherapy in locally advanced cervical cancer: Improved pelvic control and survival in RetroEMBRACE, a multicenter cohort study. Radiother Oncol. 2016;120(3):428–433. doi: 10.1016/j.radonc.2016.03.011. [DOI] [PubMed] [Google Scholar]
- 5.Mazeron R, Fokdal LU, Kirchheiner K, et al. Dose-volume effect relationships for late rectal morbidity in patients treated with chemoradiation and MRI-guided adaptive brachytherapy for locally advanced cervical cancer: Results from the prospective multicenter EMBRACE study. Radiother Oncol. 2016;120(3):412–419. doi: 10.1016/j.radonc.2016.06.006. [DOI] [PubMed] [Google Scholar]
- 6.Viswanathan AN, Erickson B, Gaffney DK, et al. Comparison and consensus guidelines for delineation of clinical target volume for CT- and MR-based brachytherapy in locally advanced cervical cancer. Int J Radiat Oncol Biol Phys. 2014;90(2):320–8. doi: 10.1016/j.ijrobp.2014.06.005. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 7.Lee LJ, Damato AL, Viswanathan AN. Clinical outcomes of high-dose-rate interstitial gynecologic brachytherapy using real-time CT guidance. Brachytherapy. 2013;12:303–10. doi: 10.1016/j.brachy.2012.11.002. [DOI] [PubMed] [Google Scholar]
- 8.Viswanathan AN, Syzmonifka J, Tempany-Afdhal CM, O’Farrell DA, Cormack RA. A prospective trial of real-time magnetic resonance-guided catheter placement in interstitial gynecologic brachytherapy. Brachytherapy. 2013;12:240–7. doi: 10.1016/j.brachy.2012.08.006. [DOI] [PubMed] [Google Scholar]
- 9.Kapur T, Egger J, Damato A, Schmidt EJ, Viswanathan AN. 3-T MR-guided brachytherapy for gynecologic malignancies. Magn Reson Imaging. 2012;30:1279–90. doi: 10.1016/j.mri.2012.06.003. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 10.NIH, HHS, NCI. Common Terminology Criteria for Adverse Events (CTCAE) Version 4.0. Jun 14, 2010. [Google Scholar]
- 11.R Core Team. R: A language and environment for statistical computing. R Foundation for Statistical Computing; Vienna, Austria: 2016. https://www.R-project.org/ [Google Scholar]
- 12.Haie-Meder C, Potter R, Van Limbergen E, et al. Recommendations from Gynaecological (GYN) GEC-ESTRO Working Group (I): concepts and terms in 3D image based 3D treatment planning in cervix cancer brachytherapy with emphasis on MRI assessment of GTV and CTV. Radiother Oncol. 2005;74:235–45. doi: 10.1016/j.radonc.2004.12.015. [DOI] [PubMed] [Google Scholar]
- 13.Viswanathan AN, Cormack R, Holloway CL, et al. Magnetic resonance-guided interstitial therapy for vaginal recurrence of endometrial cancer. Int J Radiat Oncol Biol Phys. 2006;66:91–99. doi: 10.1016/j.ijrobp.2006.04.037. [DOI] [PubMed] [Google Scholar]
- 14.Syed AMN, Puthawala AA, Abdelaziz NN, et al. Long-term results of low-dose-rate interstitial-intracavitary brachytherapy in the treatment of carcinoma of the cervix. Int J Radiat Oncol Biol Phys. 2002;54:67–78. doi: 10.1016/s0360-3016(02)02900-0. [DOI] [PubMed] [Google Scholar]
- 15.Galic V, Herzog TJ, Lewin SN, et al. Prognostic significance of adenocarcinoma histology in women with cervical cancer. Gynecol Oncol. 2012;125(2):287–91. doi: 10.1016/j.ygyno.2012.01.012. [DOI] [PubMed] [Google Scholar]
- 16.Rose PG, Java J, Whitney CW, et al. Nomograms predicting progression-free survival, overall survival, and pelvic recurrence in locally advanced cervical cancer developed from an analysis of identifiable prognostic factors in patients from NRG Oncology/Gynecologic Oncology group randomized trials of chemoradiotherapy. J Clin Oncol. 2015;33(19):2136–42. doi: 10.1200/JCO.2014.57.7122. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 17.Erickson B, Albano K, Gillan M. CT-guided interstitial implantation of gynecological malignancies. Int J Radiat Oncol Biol Phys. 1996;36:699–709. doi: 10.1016/s0360-3016(96)00373-2. [DOI] [PubMed] [Google Scholar]
- 18.Eisbruch A, Johnston CM, Martel MK, et al. Customized gynecologic interstitial implants: CT-based planning, dose evaluation, and optimization aided by laparotomy. Int J Radiat Oncol Biol Phys. 1998;40:1087–1093. doi: 10.1016/s0360-3016(98)00010-8. [DOI] [PubMed] [Google Scholar]
- 19.Viswanathan AN, Dimopoulos J, Kirisits C, Berger D, Poetter R. CT- versus MR-based Contouring in Cervical Cancer Brachytherapy: Results of a Prospective Trial and Preliminary Guidelines for Standardized Contours. Int J Radiat Oncol Biol Phys. 2007;68:491–8. doi: 10.1016/j.ijrobp.2006.12.021. [DOI] [PubMed] [Google Scholar]
- 20.Grover S, Harkenrider MM, Cho LP, et al. Image guided cervical brachytherapy: 2014 survey of the American Brachytherapy Society. Int J Radiat Oncol Biol Phys. 2016;94:598–604. doi: 10.1016/j.ijrobp.2015.11.024. [DOI] [PubMed] [Google Scholar]
Associated Data
This section collects any data citations, data availability statements, or supplementary materials included in this article.
Supplementary Materials
Kaplan-Meier Plot of Disease-Free Interval.
Disease-free interval by imaging modality utilized during brachytherapy. 2-year DFI rates were 72% and 65% in the MR-guided and CT-guided groups, respectively (p=0.87).