The Absolute Effect / Germ Cell Tumours / Imaging
After orchiectomy for stage I seminoma managed with surveillance, can MRI replace CT and can surveillance be reduced from seven scans to three without an unacceptable increase in advanced relapse?
Phase III noninferiority factorial trial in stage I seminoma after orchiectomy, with no planned adjuvant treatment. Patients were randomized to seven CTs, seven MRIs, three CTs or three MRIs.
Six-year incidence of Royal Marsden stage ≥IIC relapse (>5 cm). The noninferiority margin was 5.7 percentage points.
MRI vs CT: stage ≥IIC relapse 0.6% vs 2.6%; absolute difference −1.9 percentage points (90% CI −3.5 to −0.3). MRI therefore met noninferiority.
Three vs seven scans: stage ≥IIC relapse 2.8% vs 0.3%; absolute increase 2.5 points (90% CI 1.0–4.1), remaining below the prespecified 5.7-point margin. This supports reduced scanning while acknowledging a small increase in advanced relapse.
TRISST is primarily an imaging/surveillance de-escalation trial. It shows that MRI can replace CT and that three scans can preserve a low risk of advanced relapse while reducing cumulative imaging burden.
Journal of Clinical Oncology TRISST report.
TRISST supports MRI as an alternative to CT for surveillance after orchiectomy in stage I seminoma, and supports reducing scheduled scans from seven to three while accepting a small increase in advanced relapse that remained within the prespecified non-inferiority margin. The trial does not justify omitting surveillance or adjuvant treatment without considering the patient's stage, relapse risk, local imaging expertise and ability to attend follow-up.