Primary ovarian leiomyosarcoma: results from an analysis by the French Sarcoma Group (Ovarian SArcoma MAnagement - OSAMA Study).

Objectives: Primary ovarian leiomyosarcomas are exceptionally rare, constituting less than 1% of ovarian tumors, and they typically have a poor prognosis. The available data on the management of these tumors are sparse, with limited publications mainly comprising small retrospective series that include multiple histologic types. The aim is to evaluate the clinical, surgical, pathologic characteristics and clinical outcome of patient affected by primary ovarian leiomyosarcomas.

Methods: Using the national database (NetSarc), we conducted a retrospective study of the outcomes of primary ovarian leiomyosarcomas at 18 French Sarcoma Group centers. Patients with any International Federation of Gynecology and Obstetrics stage of primary ovarian leiomyosarcoma at first diagnosis and available follow-up were included.

Results: A total of 39 patients with primary ovarian leiomyosarcomas were included: 35 had localized disease and 4 had metastatic disease. The median tumor size was 134 mm. Radical and wide surgery was performed on 21 (62%) and 13 patients (38%), respectively. Tumor grade 3, presence of necrosis, mitoses ≥20 high-power field, and high Ki-67 expression >30% were reported in 17 of 34 (50%), 29 of 34 (85%), 17 of 34 (50%), and 17 of 27 patients (63%), respectively. Positive estrogen receptor expression was reported in 14 of 27 patients (52%), whereas progesterone receptor expression was observed in 10 of 27 patients (37%). Adjuvant chemotherapy was administered in 12 of 34 patients (35%), whereas pelvic adjuvant radiotherapy in 8 of 34 (23%). Of the early-stage primary ovarian leiomyosarcomas, 9 had isolated pelvic recurrence, whereas 18 had parenchymal distant metastases. A total of 15 patients (44%) died of disease. In early-stage primary ovarian leiomyosarcomas, high mitotic counts and progesterone receptor negativity were variables associated with worse survival.

Conclusions: Surgery is the cornerstone of treatment for early-stage primary ovarian leiomyosarcoma, whereas the role of adjuvant treatment remains unclear. Some pathologic features were associated with poorer survival. Owing to the rarity of ovarian leiomyosarcomas, referring patients to expert sarcoma centers is highly recommended.