(P 219) ELECTIVE DISCONTINUATION OF SORAFENIB TREATMENT IN DESMOID TUMORS: A RETROSPECTIVE ANALYSIS WITH IMPLICATIONS FOR CLINICAL PRACTICE

Objective: Desmoid tumors are potentially serious, painful and debilitating but non-cancerous growths with high rates of local recurrence after surgery. Treatment decisions can be complex as these tumors will often remain dormant or even spontaneously regress. Recent studies have challenged the central role of surgery in desmoid management, and many institutions will now start with active surveillance for many asymptomatic patients followed by systemic treatment when needed. In patients with symptomatic or progressive desmoid tumors, sorafenib was associated with improved sustained responses and long-term disease control compared to placebo. However, the optimal duration of treatment is not well-established and many clinicians may be reluctant to stop sorafenib in patients with responsive desmoid tumors, though sorafenib may have significant toxicity impacting quality of life.

Here we present a retrospective analysis of patients at a single institution who were treated with sorafenib and obtained disease control. These patients were followed during and after the discontinuation of treatment.

Methods: This study was a retrospective analysis of desmoid tumor patients seen at a high-volume, multidisciplinary sarcoma program from January 2021 to April, 2023. This was a retrospective review of a prospectively collected clinical database and was part of an IRB approved study. Clinical variables included whether or not patients received sorafenib, the duration of treatment, change in tumor size during treatment, reason for discontinuation and clinical outcomes after stopping treatment.

Results: Out of a total forty-six patients seen during this time period, nineteen were treated with sorafenib. All nineteen patients treated with sorafenib in this study are still alive.

One patient progressed on sorafenib. This patient, who has an aggressive tumor with an APC mutation, has now been on over ten different systemic treatment regimens and has been through multiple types of locally directed therapies. Out of the other eighteen patients treated with sorafenib, thirteen patients electively discontinued sorafenib (72%) in order to improve their quality of life and five patients are still undergoing treatment.

The average time on sorafenib prior to discontinuing the drug was 13.05 weeks, range (2-54 weeks) and standard deviation 13.74 weeks. After discontinuing sorafenib, the average length of follow-up was 21.78 months, range (7-49 months) and a standard deviation 15.75 months.

After electively stopping treatment, 53.8% of patients had stabilization of their desmoid tumor. Following discontinuation of sorafenib, 38.5% had continuous response to the drug.

Notably, one patient (7.7%) had progression of their desmoid tumor after discontinuation of sorafenib. Because this patient was followed closely, they were immediately put back on sorafenib and the patient’s disease was then stabilized.

Conclusion: The data suggests that it is safe to discontinue sorafenib for patients with desmoid tumors after a limited treatment course when there is close observation. However, it is important to recognize that one patient did have progressive disease after treatment discontinuation. In the present study the one who progressed off treatment, regained control over their disease after sorafenib was reintroduced. This emphasizes the importance of active surveillance following discontinuation of oral therapy. Further research is needed to establish the optimal treatment duration of sorafenib for patients with desmoid tumors. Collaborative efforts between institutions can provide valuable insight into patient outcomes and help guide future treatment strategies contemplating holding sorafenib.