MRI is non-inferior to CT for the surveillance of stage 1 testicular seminoma. Over a 6-year period, a 3-scan schedule is non-inferior to a 7-scan schedule, regardless of imaging modality. The use of MRI instead of CT can reduce radiation exposure in this patient population [1].   Current guidelines advocate CT surveillance following orchiectomy in patients with stage 1 testicular cancer. While this cancer has a high survival rate, there are long-term adverse health effects resulting from repeated exposure to radiation via CT scans. The phase 3 TRISST trial (NCT00589537) sought to demonstrate non-inferiority of a reduced CT schedule or MRI to safely and effectively monitor patients with stage 1 testicular cancer. Investigators randomized 669 men to 1 of 4 arms, 2 of which were monitored with CT, and 2 of which were monitored with MRI. Each imaging modality arm had 2 different frequency schedules: one scanned patients at 6, 12, 18, 24, 36, 48, and 60 months; the other scanned patients at 6, 18, and 36 months. All patients were followed for 6 years. The primary outcome measure was the proportion of patients relapsing with Royal Marsden Hospital stage ≥2C disease. Of the 669 trial participants, 82 (12%) relapsed. Only 10 of these 82 were graded as a stage ≥2C relapse. Most relapses were diagnosed at the time of scheduled imaging; additionally, relapse beyond 3 years was rare. Although there were more events in those who received 3 scans instead of 7, the criteria for non-inferiority were still met. Fewer events were observed in those who received MRI scans compared with CT. No tumor-related deaths occurred and the 5-year disease-free survival and overall survival rates were similar across all groups. Researchers asserted that surveillance is both safe and effective in stage 1 testicular seminoma, regardless of frequency or type of imaging. Furthermore, imaging beyond 3 years may actually be unnecessary, as relapse after 3 years is rare. Finally, they recommend that the standard of care should recommend MRI instead of CT, in an attempt to limit radiation exposure in this young population.

  1. Joffe J. Imaging modality and frequency in surveillance of stage I seminoma testicular cancer: Results from a randomized, phase III, factorial trial (TRISST). ASCO Genitourinary Cancers Symposium, 11-13 February 2021.