Two cycles of adjuvant carboplatin for clinical stage 1 testicular seminoma in New Zealand centres: A retrospective analysis of efficacy and long‐term events

BACKGROUND: Adjuvant carboplatin reduces relapse risk in clinical stage 1 (CS1) seminoma, though there is a paucity of long‐term safety data. AIM: Our objective was to report long‐term outcomes of two cycles of adjuvant carboplatin dosed at area under the time–concentration curve (AUC) of 7. METHODS AND RESULTS: We performed a retrospective analysis on treatment and outcomes of patients with CS1 seminoma who received adjuvant carboplatin from 2000 to 2016 at our centres in the Midland Region, New Zealand. Of 159 patients, median age 39 years, 153 received two cycles of carboplatin: 147 dosed at AUC7 and 6 at AUC6. Six patients had one cycle of carboplatin AUC7. One patient relapsed at 22 months and died of bleomycin pneumonitis 2 months after achieving a complete response with BEP chemotherapy. Neither RTI (present in 21.3%) nor tumor size >4 cm (in 43.3%) was predictive of relapse. Median follow‐up was 106 months. At 15 years, outcomes were: relapse‐free survival 99.4%, overall survival 91.4%, disease‐specific survival 100%, subsequent malignant neoplasm rate 7.6%, and second testicular germ cell tumor rate 3.85%. One patient had persistent grade 1 thrombocytopenia at 46 months. CONCLUSIONS: These data add to the body of evidence that two cycles of carboplatin AUC7 is safe and effective adjuvant treatment for CS1 seminoma.