(P 266) EFFICACY OF LIPOSOMAL DOXORUBICIN IN PATIENTS WITH INTRA- AND EXTRA-ABDOMINAL DESMOID FIBROMATOSIS

Objective: Desmoid tumors (DT) or aggressive fibromatosis are rare growths of fibroblastic connective tissue that can be locally aggressive but without metastatic potential. Most cases are sporadic, but 5-20% of cases are associated with Familial adenomatous polyposis (FAP). Despite numerous systemic options, optimal choice is unclear, and there is a paucity of studies comparing efficacy based on tumor site. Liposomal doxorubicin (LD) can be an appealing option for DT patients given its favorable schedule and toxicity profile. In this study, we compared outcomes in patients with intra-abdominal (IA) and extra-abdominal (EA) DT who received LD.

Methods: We identified patients with DT who were treated with LD between 1/2010 - 2/2022 at two sarcoma centers. Tumor and patient characteristics and outcomes were clinically (symptom improvement) and radiologically (RECIST 1.1) assessed.

Results: 40 patients with DT treated with LD were identified; 58% female and 42% male. Pt characteristics and outcomes are summarized in Table 1. Primary tumor site was IA in 21 (53%) patients. FAP was present more commonly in patients with IA vs EA DT, 8/21 (43%) and 4/19 (21%), respectively. In the IA cohort, LD was given as first (15/21, 71%), second (10%) or third (19%) line therapy. LD was used more commonly as a later line in the EA cohort with 16%, 52%, 16%, and 16% receiving it in first, second, third, and fourth lines, respectively. 37 patients received a mean of 6 cycles (range 1 - 12) and were evaluable for response. Response rate in the IA cohort treated in first-line was 50% (8 of 16) and 10 of 12 evaluable patients had symptomatic improvement. No first-line responses were seen in the EA cohort. As later lines of therapy, 7/12 patients had disease control in the second line, 6/8 patients in the third line, and 1/2 patients in the fourth line with LD in the IA cohort. 1 patient had fourth line response to LD in the EA cohort. Disease control rate with LD was 72.5% across all patients. Average time to response with LD, defined as either clinical improvement or radiographic improvement, was 23.2 weeks for all patients with IA patients responding in 17.9 compared to 29.8 weeks for EA. Duration of response was 155.6 weeks for IA and 90 weeks for EA. Reasons for discontinuation of LD included completed course with ongoing response (36.11%), Persistent Symptoms (25%), Infusion Reaction (11.11%) Progression (8.33%), Rash or Hand-Foot Syndrome (8.33%), or Other (11.11%). No acute or long-term cardiotoxicity was reported. Major side effects included: rash or hand foot syndrome (46%), infusion reaction (24%), nausea (24%), and fatigue (22%). 2 patients had no signs of recurrence or symptoms at follow-up, 33 patients were alive with symptomatic DT, 1 patient died from disease, and 3 were lost to follow-up.

Conclusion: In our study, LD provided tumor response, disease control, and symptomatic improvement regardless of location or prior therapy, with responses most frequently seen in IA DT in first line setting. Additionally, patients with IA DT had shorter time to response and longer duration of response. Further studies should include comparison of efficacy, adverse effects, and patient-reported outcomes while accounting for tumor location and line of therapy.