Imaging modality and frequency in surveillance of stage I seminoma testicular cancer: Results from a randomised, phase III, non-inferiority trial (TRISST)
Session type: E-poster/poster
Survival in stage I seminoma is almost 100%. CT surveillance is an international standard of care, avoiding adjuvant therapy. In this young population, minimising irradiation is vital. The TRrial of Imaging and Surveillance in Seminoma Testis (TRISST) assessed whether MRIs or a reduced CT schedule could be used without an unacceptable increase in advanced relapses.
TRISST was a phase III, non-inferiority, factorial trial. Eligible men had undergone orchiectomy for stage I seminoma with no adjuvant therapy planned. Randomisation was to: 7 CTs (6, 12, 18, 24, 36, 48, 60 months); 7 MRIs (same schedule); 3 CTs (6, 18, 36 months); or 3 MRIs. The primary outcome was 6-year incidence of RMH stage ≥IIC relapse (>5cm), aiming to exclude increases ≥5.7% (from 5.7% to 11.4%) with MRI (vs CT) or 3 scans (vs 7); target n=660, all contributing to both comparisons. Secondary outcomes included relapse ≥3cm, disease-free and overall survival. Both intention-to-treat and per protocol analyses were performed.
669 patients enrolled (35 UK centres, 2008-2014); mean tumour size 2.9cm, 358 (54%) low risk (<4cm, no rete testis invasion). With median follow-up 72 months, 82 (12%) relapsed. Stage ≥IIC relapse was rare (10 events). Though statistically non-inferior, more events occurred with 3 scans (9, 2.8%) vs 7 scans (1, 0.3%): 2.5% absolute increase, 90% CI (1.0%, 4.1%). Only 4/9 could have potentially been detected earlier with 7 scans. Non-inferiority of MRI vs CT was also shown; fewer events occurred with MRI (2, 0.6% vs 8, 2.5%), 1.9% decrease (-3.5%, -0.3%). Per protocol analyses confirmed non-inferiority for both comparisons. 5-year survival was 99%, similar across arms, with no tumour-related deaths.
Surveillance is a safe management approach – advanced relapse is rare, salvage treatment successful, and outcomes excellent, regardless of imaging frequency or modality. MRIs or a reduced CT schedule can be recommended to reduce irradiation.
As the largest trial in stage I seminoma, TRISST has demonstrated that patients undergoing surveillance can be effectively monitored with MRI or with fewer CT scans than currently used, with the potential to avoid harmful irradiation in this young patient group.