Semi-ResMass Study: Residual masses after salvage chemotherapy in men with pure seminoma—A multicenter retrospective analysis.

Abstract

420 Background: Only scarce data exist on the management of residual masses in men who have received two lines of chemotherapy for advanced seminoma. Due to the lack of data, the role of PET scanning, surgery and other additional treatments is controversial in these men. Methods: Data from men with pure seminoma and residual masses after salvage chemotherapy were retrospectively collected from 10 high-volume centers in 3 European countries. We analyzed the clinical management of residual masses (imaging, surgery, pathological data, and additional treatment modalities) and long-term outcomes. Residual mass was defined as a lesion of ≥1 cm after two lines of platin-based chemotherapy. Results: To date, data from 48 patients (pts) with non-progressing residual masses after second line (salvage) chemotherapy have been collected and are included in this analysis. Median age at diagnosis was 36 years (range 31; 42). A post-chemotherapy PET-FDG was performed in 32 (67%) pts. Surgery was performed in 20/48 (41%) pts irrespectively of FDG uptake (no, n=8; yes, n=5). Complete necrosis was found in 16 (80%), viable seminoma in 3 (15%), and teratoma in 1 pt, respectively. All pts with a negative PET (PET-) who underwent surgery (8/8) had complete necrosis. 5/11 pts with a positive PET (PET+) underwent surgery: 3 had a complete necrosis while 2 had viable seminoma. Among those with a PET+, 3 pts (28%) experienced either viable seminoma in residual masses or a subsequent relapse. The absence of FDG uptake correlated with absence of viable cancer (p=0.04). A second relapse occurred in 5/48 pts (10%). Only 2/20 pts who had residual masses resected post 1st salvage chemotherapy subsequently relapsed (one had viable seminoma in the residuals). At a median follow up of 4 years (IC95% [3.5-5.5]), 41/48 pts (87%) were alive. 7/48 patients died of cancer progression. Conclusions: Most men with residual masses after 1st salvage chemotherapy for advanced seminoma may achieve a cure. Pending validation with more pts in this rare situation, PET-FDG may help guide who should be selected for post-chemotherapy resection. Updated results will be presented at the congress.