Primary mediastinal seminoma: Treatment and survival outcomes.

Abstract

422 Background: Primary mediastinal pure seminoma is a rare entity and there is no clear consensus for optimal management. We report treatment and survival outcomes of patients with primary mediastinal seminoma evaluated at our institution. Methods: The Indiana University (IU) testicular cancer database was queried for patients with primary mediastinal seminoma. 21 patients evaluated at IU between 1994-2022 were included in this analysis. Kaplan-Meier methods were used for progression-free (PFS) and overall survival (OS) analysis. Results: Median age at diagnosis was 40.7 (range, 19.4-54.2). 18 (85.7%) patients were IGCCCG good risk and 3 (14.3%) were intermediate risk. Median pre-chemotherapy hCG was 10.3 (range, 0.6-1500). 12 (57.1%) patients had metastatic disease. Metastatic sites included mediastinal/supraclavicular lymph nodes in 9 patients (42.9%), lungs in 3 (14.3%), retroperitoneal lymph nodes in 3 (14.3%), brain in 1 (4.8%), liver in 1 (4.8%), adrenal gland in 1 (4.8%), kidney in 1 (4.8%) and bone in 1 (4.8%). First-line chemotherapy was BEPx3 in 9 (42.9%) patients, EPx4 in 4 (19.0%), BEPx4 in 3 (14.3%), BEPx3 + EPx1 in 2 (9.5%), VIPx4 in 2 (9.5%), and VIPx1 + BEPx3 in 1 (4.8%). With a median follow-up of 4.65 years from first-line chemotherapy start date, 3 (14.3%) patients progressed after first-line chemotherapy. Among patients who progressed, salvage 2nd line therapy was high-dose chemotherapy in 1 patient. 1 patient received more than 2 lines of therapy. 1 patient underwent surgical resection of residual mediastinal mass due to concern for local progression, with pathology revealing necrosis only. The 5-year progression-free survival (PFS) from first-line chemotherapy was 82.4% (95% CI 54.7-93.9). The 5-year overall survival (OS) was 94.1% (95% CI 65.0-99.1). At last follow-up, 20 (95.2%) patients had no evidence of disease, and 1 (4.8%) was dead of disease. Conclusions: Patients with primary mediastinal pure seminoma have high cure rates with risk adapted cisplatin-based combination chemotherapy. Despite residual masses, further surgical resection or radiation is not required in the vast majority of these patients and these residual masses can be safely monitored with surveillance.