Objective To characterize the incidence, presentation, management, and relapse of a large population of bilateral testicular germ cell tumors (TGCT) from a single institution. Patients and Methods We identified bilateral TGCT diagnosed between January 1989 and February 2014. We categorized synchronous and metachronous TGCT, noting time between first and second TGCT, histology (seminoma vs nonseminoma [NSGCT]), stage, and treatments. Kaplan-Meier survival estimates characterized relapse. Results Of 5132 patients with TGCT, 128 (2.5%) had bilateral TGCT. Bilateral TGCT increased over time—1.7% in 1989-1994 up to 3.8% in 2010 to February 2014. The 35 (27%) synchronous cases of TGCT had 20 (57%) concordant seminoma, 5 (14%) concordant NSGCT, and 10 (29%) discordant NSGCT. The 93 (73%) metachronous cases had median time interval to second TGCT of 73 months (range: 5 months-28.6 years). Compared with first TGCT, 39 (42%) had discordant histology, 29 (31%) had concordant seminoma, and 25 (27%) had concordant NSGCT. Stage at first tumor was statistically similar to second TGCT (second stage I, II, II in 69%, 22%, 10%). Increasing duration between first and second TGCT was not associated with higher stage (II or III) at second TGCT (P = .09). Treatment at first tumor was not associated with stage at second tumor. Relapse following bilateral diagnosis was 16.8% (95% confidence interval 10.5%-26.2%) at 5 years. Conclusion Incidence of bilateral TGCT increased with >25% of metachronous TGCT presenting ≥10 years after first TGCT; possible causes include increased survivorship and referral bias. Stage was statistically similar at first and second tumor; stage at second tumor was not associated with time interval between tumors or prior treatment modality at first tumor.
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