Radiotherapy versus single-dose carboplatin in adjuvant treatment of stage I seminoma: a randomised trial

Abstract

Background: Adjuvant radiotherapy is effective treatment for stage I seminoma, but is associated with a risk of late non-germ-cell cancer and cardiovascular events. After good results in initial studies with one injection of carboplatin, we undertook a large randomised trial to compare the approaches of radiotherapy with chemotherapy in seminoma treatment.

Methods: Between 1996 and 2001, 1477 patients from 70 hospitals in 14 countries were randomly assigned to receive radiotherapy (para-aortic strip or dog-leg field; n=904) or one injection of carboplatin (n=573; dose based on the formula 7x[glomerular filtration rate+25] mg), at two trial centres in the UK and Belgium. The primary outcome measure was the relapse-free rate, with the trial powered to exclude absolute differences in 2-year rates of more than 3%. Analysis was by intention to treat and per protocol. This trial has been assigned the International Standard Randomised Controlled Trial Number ISRCTN27163214.

Findings: 885 and 560 patients received radiotherapy and carboplatin, respectively. With a median follow-up of 4 years (IQR 3.0-4.9), relapse-free survival rates for radiotherapy and carboplatin were similar (96.7% [95% CI 95.3-97.7] vs 97.7% [96.0-98.6] at 2 years; 95.9% [94.4-97.1] vs 94.8% [92.5-96.4] at 3 years, respectively; hazard ratio 1.28 [90% CI 0.85-1.93], p=0.32). At 2 years' follow-up, the absolute differences in relapse-free rates (radiotherapy-chemotherapy) were -1.0% (90% CI -2.5 to 0.5) by direct comparison of proportions, and 0.9% (-0.5 to 3.0) by a hazard-ratio-based approach. Patients given carboplatin were less lethargic and less likely to take time off work than those given radiotherapy. New, second primary testicular germ-cell tumours were reported in ten patients allocated irradiation (all after para-aortic strip field) and two allocated carboplatin (5-year event rate 1.96% [95% CI 1.0-3.8] vs 0.54% [0.1-2.1], p=0.04). One seminoma-related death occurred after radiotherapy and none after carboplatin.

Interpretation: This trial has shown the non-inferiority of carboplatin to radiotherapy in the treatment of stage I seminoma. Although the absence of disease-related deaths and preliminary data indicating fewer second primary testicular germ-cell tumours favour carboplatin use, these findings need to be confirmed beyond 4 years' follow-up.