(P 253) ASSESSING THE LINK BETWEEN MYXOFIBROSARCOMA RECURRENCE AND TREATMENT ORDER: A MULTIDISCIPLINARY RETROSPECTIVE COHORT STUDY

Objective: Myxofibrosarcoma is a rare and unique subtype of soft tissue sarcomas characterized by its locally infiltrative behavior and high local recurrence rates. It accounts for approximately 5% of all soft tissue sarcomas and typically affects older adults in their sixth or seventh decade. Tumors commonly arise in the extremities and present as a slow-growing mass. Local recurrence rates are as high as 50-60% especially in cases where positive margins are present. Many prior studies have reported an association between recurrence and prior radiation for other cancers, however there is a paucity of literature specifically investigating the relationship between the site of myxofibrosarcoma recurrence and prior radiation to the site. This study examined the association between myxofibrosarcoma recurrence site and prior radiation to the area using a cohort of myxofibrosarcoma patients at the University of Miami with plans to accept data from additional institutions.

Methods: We conducted a retrospective cohort study of patients diagnosed with non-metastatic primary myxofibrosarcoma at the University of Miami from 2013 to present. Data on demographics, clinical characteristics, treatments, and outcomes were extracted from electronic medical records with attention to recurrence and whether it was local versus distant and if local whether it fell within the prior radiation field. Additionally, detailed treatment timelines were collected including the original control method and the sequence of treatments. Kaplan-Meier curves and logistical regression models were used for survival analysis. Statistical analyses were performed using R statistical programming language. The study received approval by the Institutional Review Board at the University of Miami.

Results: 40 patients diagnosed with non-metastatic at diagnosis myxofibrosarcoma were included in the study. Recurrence was observed in 22 patients (55%), 10 patients with distant recurrence (45.5%) 5 with local recurrence without prior radiation (22.7%), and 7 with local recurrence within a prior radiation field 7 (31.8%). Having a recurrence was significantly associated with decreased overall survival p = 0.039 (figure). Patients treated with radiation first had no significant affect on recurrence. Patients who received systemic therapy first had decreased odds of recurrence, OR 0.15 (95% CI of 0.03 - 0.56, p 0.007). Patients who received surgery first had increased odds of recurrence, OR 8.00 (95% CI of 1.75 - 58.69, p 0.016).

Conclusion: The findings suggest preventing recurrence will lead to improved overall survival and that having surgery first is a significant predictor of recurrence in non-metastatic myxofibrosarcoma. Radiation therapy seems to prevent recurrence at the site but additional data is needed. At the time of CTOS we plan to have additional data from collaborating institutions. We plan to use this preliminary data to further the study on effective management of sarcoma in a multidisciplinary fashion to improve patient outcomes.