(P 381) OLIGOMETASTATIC LEIOMYOSARCOMA: ASSOCIATION BETWEEN TREATMENT TYPE, METASTATIC PATTERN AND SURVIVAL

Objective: Leiomyosarcoma (LMS) is one of the most common soft tissue sarcomas, that can arise from the uterus, retroperitoneum, vessels, or extremities. Treatment of oligometastatic disease, defined as the presence of no more than five metastases in a single organ, is challenging, with site of metastases and patient status largely dictating the direction providers will take in terms of treatment, which inherently prevents this disease from having a definitive treatment plan and outlook of prognosis. Multidisciplinary treatment approaches have trialed local versus systemic options, including surgery, chemotherapy, and radiation. The diverse nature of oligometastatic LMS prompted us to study whether overall survival (OS) and progression free survival (PFS) differs between sites of metastases and type of treatment received.

Methods: This single-center retrospective study evaluated consecutive patients with biopsy-proven LMS with oligometastatic disease between January 2009 to May 2024. Data regarding clinical presentation at diagnosis (localized vs oligometastatic disease), type of LMS (uterine vs soft tissue), sites of metastases (peritoneum, pelvis, lung, lymph nodes, liver, bone) type of treatment received (chemotherapy, surgery, radiation, various combinations of each), progression free survival (PFS) and overall survival (OS) were collected. Associations between sites of metastases, type of treatment received, LMS type, were performed using Fisher’s exact or Chi square test. Progression free survival (PFS) and overall survival (OS) curves for sites of metastases and treatment type were estimated using Kaplan-Meier curves and subsequently compared to a log-rank test. Cox proportional hazard regression models were utilized to study the association between PFS and OS with sites of metastases and treatment type. The location for metastases was grouped into lung versus abdominopelvic metastases (which included liver, pelvis, peritoneum, and lymph nodes), while treatment type was grouped into systemic versus local treatment (which included surgery, IR/ablation, and radiation). If patients received both systemic and local treatment, they were placed in the “local” treatment group.

Results: 28 subjects were evaluated (F/M:20/8; median age at diagnosis 62 years). 15/28 (54%) subjects had soft tissue LMS and 13/28 (46%) had uterine LMS. The most common site of oligometastatic disease was the lung (16/28, 57%), followed by the liver (5/28, 18%), peritoneum (3/28, 11%), and lymph nodes (2/28, 7%). The treatment type that was most commonly systemic (10/28, 37%), followed by surgery only (4/28, 15%), and combined surgery and chemotherapy (3/28, 11%). Oligometastatic disease to the lung was associated with a longer OS (p = 0.04) and PFS (p = 0.02) compared to abdominopelvic metastases. Oligometastatic disease to the abdominal or pelvic organs was also associated with shorter PFS compared to lung metastases on Cox analysis (Risk Ratio: 4.9; 95% CI: 1.14, 21.9; p = 0.03). No significant difference in OS or PFS was observed between patients with local versus systemic treatment types (p = 0.35 and 0.12, respectively).

Conclusion: The variable presentation and progression of oligometastatic LMS has brought immense challenges in identifying prognostic markers and identifying effective treatment plans for patients. In this study, both PFS and OS were increased in subjects with lung metastases. This study highlights the need for prospective studies to assess treatment strategies with local vs systemic therapy for this patient population with a goal of creating a more standardized approach.