Abstract
Objective
In this study, we aimed to describe the clinical features, management, and outcomes of desmoid tumors (DTs) in familial adenomatous polyposis (FAP) patients at a high-volume sarcoma center.
Methods
Consecutive patients with FAP and DTs were identified from our institutional databases (1985–2021). Patient demographics, treatment, and outcomes were described. Categorical data were compared using Fisher’s exact test, and Kaplan–Meier curves were used to estimate progression-free survival (PFS).
Results
Forty-five patients with 67 DTs were identified: 39 mesenteric or retroperitoneal (58.2%), 17 abdominal wall (25.4%), 4 extremity (6%), 4 breast (6%) and 3 back (4.4%). Severe DT symptoms were present in 12 patients (26.7%). Initial treatments per tumor were observation in 30 (44.8%) DTs, chemotherapy in 15 (22.4%) DTs, surgery in 10 (14.9%) DTs, and other systemic therapies in 10 (14.9%) DTs. The majority of DTs remained stable with observation or a single intervention (77.8%). Median PFS was 23.4 years (95% confidence interval 7.6–39.2). In the 12 severely symptomatic patients, four patients required more than two interventions for DT control. At a median follow-up of 6.0 years (range 0.7–35.8 years), 33 (73.3%) patients were alive with disease, 7 (15.6%) were alive without disease, and 5 (11.1%) died of other causes. No patients died of DT-related complications.
Conclusions
The majority of DTs in FAP patients remained stable with observation or a single intervention. There were no DT-related deaths; however, 12 of 45 patients (26.7%) experienced significant tumor morbidity and required more interventions for disease control. Further studies on quality of life are required.
Supplementary Information
The online version contains supplementary material available at 10.1245/s10434-023-13675-1.
Desmoid tumors (DTs), also known as aggressive fibromatoses, are an uncommon soft tissue neoplasm composed of a proliferation of bland fibroblasts with minimal atypia. Although they do not metastasize, DTs can be locally aggressive, with the potential for significant morbidity and mortality.1 DTs can arise throughout the body, most frequently presenting in the abdominal wall (AW), extremity, chest, and intra-abdominal regions. The vast majority of DTs (90–95%) arise sporadically as a result of a somatic mutation in the CTNNB1 gene, but a subset occurs in patients with familial adenomatous polyposis (FAP) and are related to germline APC gene mutations. Patients with FAP have a > 800-fold risk of developing DTs relative to the general population2 and have a greater tendency to develop multiple tumors, progressive disease, and intra-abdominal location of tumors.3 As such, DTs represent an important cause of morbidity and mortality in patients with FAP, particularly in patients who have undergone colectomy to reduce the risk of colorectal cancer.
Specific germline mutations in the APC gene have been recognized to be associated with various phenotypic expressions in FAP. For instance, mutations at the 5′ end of the gene tend to be associated with attenuated FAP, while mutations in codon 1309 (3′ end) have been linked to younger age of FAP onset.4–7 Previous studies have shown that DTs tend to be associated with mutations at the 3′ end, in particular between codons 1444–1580.5,8,9 Church et al.10 also showed that mutations 3′ of codon 1399 were associated with more symptomatic and severe disease.
Our institutions are tertiary care centers that receive high volumes of referrals of DT patients with and without FAP. This study presents a unique opportunity to investigate the characteristics, management, and outcomes of our population of FAP patients with DTs.
Methods
Consecutive patients with documented diagnoses of both FAP and DTs managed at our centers between 1985 and 2021 were identified from two prospectively maintained institutional databases: the Familial Gastrointestinal Cancer Registry (FGICR), which tracks patients with inherited polyposis as well as other hereditary gastrointestinal cancer conditions such as Lynch syndrome, and the Toronto Sarcoma Database, which documents patients with benign and malignant soft tissue tumors. These databases are maintained at Mount Sinai Hospital and Princess Margaret Cancer Centre, respectively. Institutional Research Ethics Board (REB) approval was obtained to collect data regarding demographics, diagnosis, treatment and outcomes. Patients were included if they had a minimum follow-up of 6 months from initial treatment. When data were missing or incomplete, patient electronic charts were reviewed to complete the data collection.
DTs were grouped and analyzed by body site as follows: mesenteric/retroperitoneal (M/RP), AW, extremity, back, and breast. When an individual patient had multiple sites of tumor involvement, symptom and management data were collected separately for each site. Decision making surrounding observation versus active intervention as initial treatment was not regularly included in the notes. Progression was defined as clinical or radiological tumor progression and/or worsening of symptoms (e.g., pain, small bowel obstruction [SBO], etc.). Symptoms at the time of diagnosis, prior to the start of any treatment, included a sensation of a palpable mass, pain, abdominal fullness, bowel or ureteric obstruction, intra-abdominal abscesses, and stoma retraction. Severe symptoms were defined as recurrent SBOs requiring hospitalization, abscesses, fistulas, or ureteric obstructions requiring intervention. After diagnosis, patients were monitored with regular imaging (computed tomography [CT] scans and/or magnetic resonance imaging [MRI]), particularly for RP/mesenteric locations. Tumors that progressed either on imaging and/or symptomatically were treated early, most commonly with systemic treatment first. The majority of treatment decisions were made in the context of the multidisciplinary team (MDT).
Data were analyzed using descriptive statistics. Categorical data were compared using Fisher’s exact test, and Kaplan–Meier curves were used to estimate progression-free survival (PFS).
Results
In total, 45 patients with 67 DTs were identified and included in our study population. The characteristics of patients are summarized in Table 1, while the characteristics of individual tumor sites are summarized in Table 2.
Table 1.
Characteristics of the patient population
| N | % | |
|---|---|---|
| FAP patients | 45 | 100 |
| Patients with desmoid tumors at multiple sites | 13 | 29 |
| Female | 25 | 56 |
| Age at FAP diagnosis, years | ||
| ≤ 20 | 17 | 38 |
| 21–30 | 8 | 18 |
| 31–40 | 5 | 11 |
| 41–50 | 6 | 13 |
| Unknowna | 9 | 20 |
| Known diagnosis of FAP before the earliest desmoid diagnosis | 41 | 91 |
| Colon surgery performed for FAP | 43 | 96 |
| Median age at surgery for FAP (range) | 27 (16–48) | |
| Median age at earliest desmoid presentation (range) | 32 (14–58) | |
| Symptomatic at any timepoint | 32 | 71 |
| Severely symptomaticb | 12 | 27 |
| Documented APC mutation | 40 | 89 |
| APC mutation pre codon 1399 | 7 | 18 |
| APC mutation post codon 1399 | 33 | 83 |
| Patients with any intra-abdominal desmoid tumors | 39 | 87 |
| Number of interventions required for desmoid control | ||
| 0 (observation only) | 13 | 29 |
| 1 | 22 | 49 |
| 2 | 5 | 11 |
| 3 | 3 | 7 |
| Unknown | 2 | 4 |
| Treatments receivedc | ||
| Chemotherapy | 19 | 42 |
| Other systemic | 9 | 20 |
| Surgery | 10 | 22 |
| Radiation | 2 | 4 |
FAP familial adenomatous polyposis, SBO small bowel obstruction
aAll FAP cases were diagnosed under the age of 50 years, but in some cases the exact age was not documented
bSevere symptoms = recurrent SBO requiring hospitalization, abscess/fistula, ureteric obstruction requiring intervention
cSome patients received multiple types of treatment
Table 2.
Characteristics of individual tumor sites
| N | % | |
|---|---|---|
| Distinct desmoid tumor sites | 67 | 100 |
| Original presentation | ||
| Symptomatic | 32 | 48 |
| Incidentally identified | 32 | 48 |
| Unknown | 3 | 4 |
| Site of desmoid(s) | ||
| Mesenteric/retroperitoneal | 39 | 58 |
| Abdominal wall | 17 | 25 |
| Extremity | 4 | 6 |
| Breast | 4 | 6 |
| Back/paraspinal | 3 | 4 |
| Initial intervention | ||
| Observation | 30 | 45 |
| Surgery | 10 | 15 |
| Chemotherapy | 15 | 22 |
| Other systemic | 10 | 15 |
| Unknowna | 2 | 3 |
| Best response to initial intervention | ||
| No evidence of disease | 8 | 12 |
| Residual disease (stable or regressed) | 43 | 64 |
| Progressive disease | 10 | 15 |
| Unknown | 6 | 9 |
aInitial treatment administered elsewhere, not documented in the notes
Demographics and Baseline Patient Characteristics
Of the 45 patients, the majority were female (56%, n = 25), were 30 years of age or younger at the time of FAP diagnosis (67%, n = 30), and had a known diagnosis of FAP before their earliest DT was identified (91%, n = 41). At the time of first DT diagnosis, 40 patients (89%) had undergone surgery (subtotal colectomy or total proctocolectomy) for FAP. Median age at surgery for FAP was 27.0 years (range 16–48 years) and median age at earliest DT presentation was 32.0 years (range 14–58 years). A germline APC mutation was documented in 40 of 45 patients (89%). Data regarding race/ethnicity were not available in the databases as per institutional policy.
Desmoid Tumor (DT) Features
Thirteen patients (29%) developed DTs in multiple body sites during the study period (range 2–5 sites). The 67 individual DT locations were distributed as follows: 39 (58%) M/RP, 17 (25%) AW, 4 (6%) extremity, 3 (4%) back/paraspinal, and 4 (6%) breast. M/RP tumors were present in 39 patients (87%). The most common site of initial DT diagnosis was M/RP (29 patients, 64%) followed by AW (9 patients, 20.0%), breast (2 patients, 4%), and extremity (1 patient, 2%), while 4 patients (9%) initially presented with DTs in multiple body sites. At initial presentation, 32 DTs were associated with symptoms (48%), 32 DTs were identified incidentally, and for 3 DTs, the presence of symptoms was not recorded. Ultimately, 41 tumors (61% of tumors) were associated with symptoms in 32 patients (71% of patients).
Of 44 patients with M/RP or AW tumors, 43 (98%) underwent surgery for FAP prior to their earliest M/RP or AW diagnosis; of these procedures, 33 (77%) were open, 7 (16%) were laparoscopic, and in 3 patients, the surgical approach was not documented. Twenty-five of these patients developed symptoms related to their M/RP or AW DTs (69%). There was no significant difference in the frequency of symptom development between patients who were treated by an open versus laparoscopic approach (72% vs. 60%, p = 0.618). All 12 severely symptomatic patients underwent open surgery for FAP before developing their earliest M/RP or AW DT.
Management of Individual Patients
In 34 of 45 patients (76%), DTs were controlled with either observation or a single intervention. In these 34 patients with stable or regressed disease after observation or a single initial intervention, median PFS was 23.4 years (95% confidence interval [CI] 7.6–39.2) [Fig. 1]. Additional treatments included further chemotherapy, other systemic therapy, or radiation therapy (Fig. 2).
Fig. 1.
a Overall survival; b progression-free survival
Fig. 2.
Overview of treatment for individual tumors. Chemo chemotherapy, RT radiation therapy
Patients initially observed were significantly more likely to progress than those treated with any therapy (31% vs. 3%, p = 0.005). However, 20% of all patients remained stable with observation alone, with no progression of their disease over a median follow-up of 8.2 years (range 3.2–32 years). Patient- and tumor-related characteristics per initial treatment group are shown in electronic supplementary Table 1.
Nine patients were originally treated with surgery. Of these, three patients presented with a palpable breast mass and three patients presented to our institute after desmoid resection elsewhere (two AW, one M/RP). The rationale for surgery was not documented in these patients. Two patients underwent surgery for other reasons (one for FAP and one for stoma closure) and the desmoid was removed incidentally. Finally, one patient underwent excision of an RP desmoid that was causing ureteric obstruction.
Systemic therapy was administered as initial treatment in 15 of 45 patients (33%): nine patients had M/RP tumors, three patients had AW tumors, and three patients had both M/RP and AW tumors. Of these 15 patients, nine received methotrexate and vinorelbine/vinblastine (MV), four received tamoxifen, one received toremifene, and one patient received sulindac. Three patients (20%) required additional treatment due to disease progression; initial treatments were MV (discontinued after 8 months due to coronavirus disease 2019 [COVID-19] treatment restrictions), tamoxifen and sulindac, requiring further treatment, after which no further recurrences or progression developed.
Additionally, 10 patients (22%) were treated with systemic therapy after initial observation (six patients) or previous surgery (four patients): nine with M/RP and/or AW tumors and one with breast tumors. Patients who were initially observed were all treated for disease progression at the primary disease site, while patients after previous surgery were treated for tumors developing at new locations. Of these, eight patients received MV, one received toremifene, and one patient received sorafenib. Disease progression was observed in three patients, who were subsequently treated with sorafenib without further recurrences or progression.
Severe symptoms, defined as recurrent SBO requiring hospitalization, abscess/fistula formation, or ureteric obstruction requiring intervention were present in 12 patients (27%). In these 12 severely symptomatic patients, four required two to four interventions for DT control (one of these patients continued to progress after their most recent therapy).
There was no association between the location of the mutation in the APC gene and the number of DTs that patients developed (p = 0.31) [Table 3]. Patients with germline mutations in exon 15 of the APC gene required two or more interventions (including observation) in 43% of cases (12/28), compared with 10% (1/10) in patients with mutations in other exons (p = 0.06) [Table 4]. There was no difference in the percentage of patients receiving observation or another intervention as their first-line treatment between the different mutation location groups (p = 0.64) [Table 5]. Finally, in patients initially treated with observation, 47% of patients with an exon 15 mutation eventually required additional treatment, while none (0/5) of the patients with a mutation in one of the other exons required additional treatment after observation (p = 0.11) [Table 6].
Table 3.
Patients classified by germline mutation and number of desmoid tumors
| Exon | Single DT | Multiple DTs | Total |
|---|---|---|---|
| 5 | 0 | 1 | 1 |
| 6 | 2 | 1 | 3 |
| 8 | 2 | 0 | 2 |
| 10 | 0 | 1 | 1 |
| 11 | 1 | 0 | 1 |
| 12 | 0 | 1 | 1 |
| 14 | 1 | 0 | 1 |
| 15 | 21 | 9 | 30 |
| Total | 27 | 13 | 40a |
Pearson Chi-square; p = 0.31
DTs desmoid tumors
aIn 5 of 45 patients, germline mutations in the APC gene were not documented
Table 4.
Patients classified by germline mutation and number of interventions
| Exon(s) | Single intervention (including observation) | Two or more interventions | Total |
|---|---|---|---|
| 5–14 | 9 | 1 | 10 |
| 15 | 16 | 12 | 28 |
| Total | 25 | 13 | 38a |
Fisher’s exact test; p = 0.06
aIn 5 of 45 patients, germline mutations in the APC gene were not documented, and in 2 additional patients, the total number of interventions required for desmoid control was not known
Table 5.
Patients classified by germline mutation and initial treatment
| Exon(s) | Initial observation | Other initial intervention | Total |
|---|---|---|---|
| 5–14 | 5 | 5 | 10 |
| 15 | 15 | 15 | 30 |
| Total | 20 | 20 | 40a |
Fisher’s exact test; p = 0.64
In 5 of 45 patients, germline mutations in the APC gene were not documented
Table 6.
Patients initially treated with observation classified by germline mutation and the need for further interventions
| Exon(s) | Observation only | Further interventions | Total |
|---|---|---|---|
| 5–14 | 5 | 0 | 5 |
| 15 | 8 | 7 | 15 |
| Total | 13 | 7 | 20 |
Fisher’s exact test; p = 0.11
At a median follow-up of 6.0 years (range 0.7–35.8 years), 33 (73%) patients were alive with disease, 7 (16%) were alive without disease, and 5 (11%) died of non-DT-related causes. No patients died of DTs or treatment-related causes during the follow-up period. The outcomes of individual patients are summarized in Fig. 3.
Fig. 3.
Overview of treatment for individual patients. This swimmer plot represents the treatment courses of individual patients. Individual treatments are denoted as bars, while the length of the bars represent the length of treatment. The grey lines represent the periods of active observation. Of note, three patients had missing start and/or end dates of treatment and were therefore excluded from this figure
Management of Individual DTs
Individual DTs were initially treated with observation in 30 tumors (46%), chemotherapy in 15 tumors (23%), surgery in 10 tumors (15%), and other systemic therapy, such as sorafenib, tamoxifen, or sulindac, in 10 tumors (15%). Among the 10 tumors that were resected, 2 tumors were incidentally resected during surgery for other reasons.
The best tumor response to initial intervention (including observation) was no evidence of disease in 8 tumors (13%), residual disease (stable or regressed) in 43 tumors (71%), and progressive disease in 10 tumors (16%).
Discussion
This paper offers one of the largest published series documenting characteristics, management, and outcomes of DTs in patients with FAP, a very high-risk patient population, often excluded from DT studies. The majority of patients achieved DT disease control with observation or a single intervention. Most were asymptomatic or experienced mild to moderate symptoms. However, few patients had complete regression of their disease and, as such, most patients required prolonged ongoing surveillance and follow-up with their sarcoma team. This, in addition to the separate follow-up required with the gastrointestinal team for surveillance of polyps and/or complications from surgical pouch procedures, highlights the magnitude of resources that must be devoted to the management of so-called benign desmoid disease in patients with FAP.
Our findings corroborate those established in the literature with respect to the propensity of FAP-associated DTs to develop intra-abdominal disease, multiplicity of tumors, preponderance of presentation under age 30 years, and nearly balanced incidence between males and females. These characteristics are distinguishable from sporadic DTs, which tend to be single-site tumors, more common in females, involve the AW or extra-abdominal sites, and have a wider distribution of age at presentation.11
In contrast to the reported DT-associated mortality rate of 7.5–14% in FAP patients,3,12,13 our series had no deaths directly attributable to DTs during the follow-up period. The reasons for this discrepancy may be the liberal use of methotrexate-based chemotherapy in our population, and early intervention. As demonstrated by a recent multi-institutional European study investigating the outcomes of FAP-related DTs treated with low-dose methotrexate and vinca alkaloids, this chemotherapy regimen is safe and effective in this patient population.14 Similar to our findings, that study reported no DT-associated deaths over a median follow-up of 5.4 years. Another factor that likely minimized mortality in our patient group was the application of a specialized multidisciplinary team approach. This was especially relevant in the most severely symptomatic patients. While most of our patients fared relatively well with respect to control of their DTs with one or fewer discrete interventions, a sizeable minority experienced severe symptoms requiring multiple hospital admissions and interventions, both for disease control and symptom relief. The success of this approach highlights the critical role played by multidisciplinary communication and collaboration in the management of this disease.
An additional finding of interest was the association between likelihood of progression and location of germline APC mutation in exon 15. More than 80% of patients in our cohort in whom genetic testing was performed carried a mutation at the 3′ end of the APC gene. This is consistent with previous studies that have shown that mutations in the 3′ region of the APC gene result in a higher incidence of DTs in FAP patients.5,8,15 Others have also shown increased severity of DT phenotype (defined by size, symptoms, and growth) in patients with mutations 3′ to codon 1399.10 Although we found no significant association between the presence or severity of symptoms and site of APC mutation in our patient set, our patient numbers are likely too small to comment definitively on this correlation. It may be worthwhile to investigate this question further to determine whether the specific site of mutation in the APC gene can guide the closeness of monitoring and/or aggressiveness of DT management.
The strengths of this study include a relatively large patient cohort with a long follow-up period and a high rate of documentation of germline mutations. A limitation is the incomplete documentation of some data points in the clinical chart (e.g. less severe symptoms, pain medication administered on an outpatient basis, size of desmoids at various time points), which could not be taken into account in the analysis. Furthermore, the rationale for observation versus active intervention for DTs was not always documented and potentially varied, both between caregivers and over the course of the 25-year study period.
Although this study did show that most patients with FAP-associated DTs achieved adequate and long-lasting disease control with observation or a single intervention, some important questions remain unanswered. First, this study does not identify which patients would benefit from early initiation of treatment (as opposed to observation), and second, this study does not answer the important question of which treatment modality would be preferred once disease progression has been established. Therefore, further research is needed to better help guide clinical decision making.
Conclusions
The majority of patients with FAP-associated DTs achieved disease control with observation or a single intervention. Tumors initially observed were more likely to progress, particularly when associated with an exon 15 APC mutation. However, all progressing tumors were well-controlled once treatment was initiated. While there were no disease-related deaths, some 27% of patients did experience significant morbidity. Further research is needed to better determine which treatment modality should be followed once disease progression has been established.
Supplementary Information
Below is the link to the electronic supplementary material.
Acknowledgment
The authors would like to thank Vanessa Di Gioacchino (MSc, CGC) for her assistance with the interpretation of APC mutational analysis and nomenclature.
Disclosure
None.
Footnotes
Publisher's Note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Eisar Al-Sukhni and Joel Shapiro contributed equally to this work.
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