708MO - Metachronous contralateral testicular cancer in the cisplatin era: A population-based cohort study

Background

It is hypothesized that cisplatin-based chemotherapy (CT) reduces the occurrence of a metachronous contralateral (second) germ cell testicular cancer (TC). However, data regarding treatment details are lacking in previous publications. The aim of this study was to investigate the risk of a second TC in relation to previous TC treatment, in particular the number of cisplatin-based CT cycles.

Methods

A population-based cohort of 5622 men diagnosed with first TC 1980-2009, as well as second TC, was identified by the Cancer Registry of Norway. Treatment data were based on medical records. Cumulative incidence of metachronous contralateral TC was estimated, and standardized incidence ratios (SIRs) were calculated to compare the risk to the general population. The effect of treatment intensity on the second TC risk was investigated using Cox regression.

Results

Median follow-up was 16.3 years, during which 206 men were diagnosed with a second TC after median 5.9 years. Median time to second TC was shorter after CT (5.5 years) than after surgery only (6.6 years). Overall, the 20-year crude cumulative incidence was 4.0% (95% CI 3.5-4.6), with lower incidence after CT (3.1 %, 95% CI 2.4-3.9) than after surgery only (5.7%, 95% CI 4.4-7.3). The second TC incidence was also lower for those >=30 years (2.8%, 95% CI 2.2-3.4) at first TC diagnosis than those <30 years (6.0 %, 95% CI 4.9-7.1). Overall, the risk of a second TC was 13-fold higher compared with the risk of developing TC in the general population (SIR 13.3, 95% CI 11.6-15.3). The SIR was lower after CT (9.1, 95% CI 7.1-11.6) than after surgery only (17.1, 95% CI 13.6-21.7). With surgery only as reference, treatment with CT significantly reduced the risk of a second TC (HR 0.52, 95% CI 0.37-0.73). For each cisplatin-based CT cycle administered, the risk for a second TC decreased monotonously, with significantly reduced risks after 3, 4 and >4 cycles (HRs 0.45, 0.41, and 0.21 respectively).

Conclusions

The overall 20-year cumulative incidence of a second TC was 4.0%. Age at first TC diagnosis as well as treatment intensity influenced the risk of a second TC, with a monotonic risk reduction for each additional cisplatin-based CT cycle administered.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

Translational Cancer Research Group, Department of Clinical Medicine, UiT The Arctic University of Norway.

Funding

Helse Nord RHF.

Disclosure

All authors have declared no conflicts of interest.