Initial results of a randomized trial comparing carboplatin with radiotherapy (RT) as adjuvant treatment for stage I seminoma found carboplatin had a noninferior relapse-free rate (RFR) and had reduced contralateral germ cell tumors (GCTs) in the short-term. Updated results with a median follow-up of 6.5 years are now reported.
Patients and Methods
Random assignment was between RT and one infusion of carboplatin dosed at 7 x (glomerular filtration rate + 25) on the basis of EDTA (n = 357) and 90% of this dose if determined on the basis of creatinine clearance (n = 202). The trial was powered to exclude a doubling in RFRs assuming a 96-97% 2-year RFR after radiotherapy (hazard ratio [HR], approximately 2.0).
Results
Overall, 1,447 patients were randomly assigned in a 3-to-5 ratio (carboplatin, n = 573; RT, n = 904). RFRs at 5 years were 94.7% for carboplatin and 96.0% for RT (RT-C 90% CI, 0.7% to 3.5%; HR, 1.25; 90% CI, 0.83 to 1.89). One death as a result of seminoma (in RT arm) occurred. Patients receiving at least 99% of the 7 x AUC dose had a 5-year RFR of 96.1% (95% CI, 93.4% to 97.7%) compared with 92.6% (95% CI, 88.0% to 95.5%) in those who received lower doses (HR, 0.51; 95% CI, 0.24 to 1.07; P = .08). There was a clear reduction in the rate of contralateral GCTs (carboplatin, n = 2; RT, n = 15; HR, 0.22; 95% CI, 0.05 to 0.95; P = .03), and elevated pretreatment follicle-stimulating hormone (FSH) levels (> 12 IU/L) was a strong predictor (HR, 8.57; 95% CI, 1.82 to 40.38).
Conclusion
These updated results confirm the noninferiority of single dose carboplatin (at 7 x AUC dose) versus RT in terms of RFR and establish a statistically significant reduction in the medium term of risk of second GCT produced by this treatment.
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