(P 158) SORAFENIB OR ANTHRACYCLINE-BASED CHEMOTHERAPY IN ADULT PATIENTS WITH PROGRESSIVE DESMOID TUMORS

Objective: Desmoid tumors are soft tissue neoplasms that, although unable to metastasize, can cause significant morbidity due to local infiltration. Occasionally, they may lead to death due to fast growth compromising vital structures. In this context, a more robust and timely response is required. Although the therapeutic arsenal for desmoid tumors is growing, no randomized controlled trials compare the efficacy of different systemic therapies. Here we aim to compare anthracycline-based regimens and sorafenib to assess efficacy, response rates, and time to response.

Methods: We conducted a retrospective comparative analysis across three academic sites to evaluate the outcomes of patients with desmoid tumors who received either sorafenib or anthracycline-based therapy over a one-year period. The primary endpoint was investigator-assessed progression-free survival. The secondary endpoints were objective response rates (assessed using RECIST 1.1 criteria), time to response, and adverse events (graded according to CTCAE). Kaplan-Meier and log-rank tests were used to estimate progression-free survival and compare time to response.

Results: From 2005 through 2022, a total of 54 patients received sorafenib and 38 anthracycline-based therapy. Baseline characteristics for both groups are detailed in Table 1. The 1-year progress-free survival rate was 61% (95% confidence interval [CI], 43 to 79) for the anthracycline-based group and 59% (95% CI, 44 to 74) for the sorafenib group, which was not statistically different (p = 0.75), which remained not different in pre-specified subgroup analyses (sex, tumor location, previous surgery, and previous systemic therapy). The percentage of patients who had an objective response at 1 year was 34% with anthracycline-based therapies and 19% with sorafenib (p=0.34), with a median time to response of 4 months on the anthracycline-based group and 6.5 months on the sorafenib. In the sorafenib group, the most frequently reported adverse events were grade 1 or 2 events of hand-foot syndrome (40%), fatigue (26%), diarrhea (22%), and hypertension (13%). In the anthracycline-based group, grade 1 or 2 events of nausea (34%), rash (23%), fatigue (18%), and mucositis (13%). G3 events were higher in the anthracycline-based group, 26% vs. 9% (p < 0.05), although only 18% of patients discontinued therapy due to side effects in the anthracycline-based group compared to 24% in the sorafenib group.

Conclusion: Among patients with progressive or symptomatic desmoid tumors, anthracycline-based therapy and sorafenib did not show statistically significant differences in progression-free survival rates, response rate, or time to response. An important limitation of the findings is the small group sizes and no centralized radiological review, which may lead to inter-reader variability during RECIST evaluation.