First Indicator of Relapse in Testicular Cancer and Implications for Follow-up: Analysis of the Swiss Austrian German Testicular Cancer Cohort Study (SAG TCCS).

Background and objective: Follow-up for patients with testicular cancer should ensure early detection of relapses. Optimal schedules and minimum requirements for cross-sectional imaging are not clearly defined, and guideline recommendations differ. Our aim was to analyse the clinical impact of different imaging modalities for detection of relapse in a large prospective cohort (Swiss Austrian German Testicular Cancer Cohort Study, SAG TCCS). Methods: Patients with seminoma or nonseminoma were prospectively enrolled between January 2014 and February 2023 after initial treatment ( Key findings and limitations: We analysed data for 1006 patients (64% seminoma, 36% nonseminoma); 76% had stage I disease. Active surveillance was the most frequent management strategy (65%). Recurrence occurred in 82 patients, corresponding to a 5-yr relapse-free survival rate of 90.1% (95% confidence interval 87.7-92.1%). Median follow-up for patients without relapse was 38.4 mo (interquartile range 21.6-61.0). Cross-sectional imaging of the abdomen was the most important indicator of relapse 57%, abdominal CT accounting for 46% and MRI for 11%. Marker elevation indicated relapse in 24% of cases. Chest X-ray was the least useful modality, indicating relapse in just 2% of cases. Conclusions and clinical implications: On the basis of findings from our prospective register, we have adapted a follow-up schedules with an emphasis on abdominal imaging and a reduction in chest X-rays. This schedule might provide additional guidance for clinicians and will be prospectively evaluated as SAG TCCS continues to enrol patients. Patient summary: We analysed the value of different types of imaging scans for detection of relapse of testicular cancer. We used our findings to propose an optimum follow-up schedule for patients with testicular cancer.