Adjuvant carboplatin for clinical stage I testicular seminoma in New Zealand centers: Retrospective analysis of efficacy and long-term adverse effects.

Abstract

e16041 Background: Adjuvant carboplatin reduces relapse risk in clinical stage I (CS1) testicular seminoma, though there is a paucity of long-term safety data. While some studies report that two cycles is more effective than one, there is no randomised trial evidence or consensus on the optimal number of cycles. European guidelines recommend a risk-based approach to consider adjuvant carboplatin in those with either rete testis involvement (RTI) or tumour size > 4cm, and surveillance for other patients. We report long-term outcomes of 2 cycles of adjuvant carboplatin dosed at area under the curve (AUC) of 7 as standard management of CS1 seminoma since 2000. Methods: We performed a retrospective analysis on treatment and outcomes of patients with CS1 seminoma who received adjuvant carboplatin from 2000 to 2016 at the Waikato, Lakes and Bay of Plenty District Health Boards. We also collected information on mortality, causes of death and subsequent malignant neoplasms (SMN). Results: Of 160 patients, median age 39 (range 20-73) years, 154 received 2 cycles of carboplatin: 148 dosed at AUC7 and six at AUC6; another six patients had one cycle of carboplatin AUC7, curtailed due to toxicity in 3 patients. Two relapses occurred: one at 10 months (in hindsight stage 2a at diagnosis) and one at 22 months (died of pulmonary embolism 2 months after achieving complete response with BEP chemotherapy). Neither RTI (present in 21.3%) nor tumour size > 4cm (in 43.1%) were predictive of relapse. No patients died of seminoma. At median follow up of 109 (range 17-209) months, relapse-free survival was 98.7%, overall survival was 97.5% and disease-specific survival was 100%. A SMN occurred in 11 patients (6.9%) at median 96 months and caused 4 deaths (melanoma, myeloma, small cell lung cancer and glioblastoma); 4 patients (2.6%) had a contralateral testicular germ cell tumour (at median 69 months). One patient had persistent grade 1 thrombocytopenia at 46 months. Conclusions: This data adds to the body of evidence that two cycles of carboplatin AUC7 is safe, effective adjuvant treatment for CS1 seminoma. It did not have significant long-term adverse effects in our population.