ASCO GU 2021: TRISST: Imaging Modality and Frequency in Surveillance of Stage I Seminoma Testicular Cancer: Results from a Randomized, Phase III, Factorial Trial

( Survival after orchiectomy in stage I seminoma is almost 100% and the use of CT surveillance is an international standard of care, avoiding adjuvant therapy. In this young population, who are unlikely to die from testicular cancer, minimizing irradiation is vital. The Trial of Imaging and Surveillance in Seminoma Testis (TRISST, NCT00589537), assessed whether CTs can safely be reduced, or replaced with MRI, without an unacceptable increase in advanced relapses. At the GU ASCO 2021 annual meeting, Dr. Robert Huddart and colleagues presented results from the TRISST trial.

TRISST is a phase III, multicenter, non-inferiority, factorial trial. Eligible men had undergone orchiectomy for stage I seminoma with no adjuvant therapy planned. Randomization was to:

  • 7 CTs: 6, 12, 18, 24, 36, 48, 60 months after randomization
  • 7 MRIs: 6, 12, 18, 24, 36, 48, 60 months after randomization
  • 3 CTs: 6, 18, 36 months after randomization
  • 3 MRIs: 6, 18, 36 months after randomization

Follow-up for the trial was for 6 years with a primary outcome of 6-year incidence of stage ≥IIC relapse, aiming to exclude an increase ≥5.7% (from 5.7% to 11.4%) with MRI (versus CT) or 3 scans (versus 7). The target sample size was 660 patients, all contributing to both comparisons. Secondary outcomes include relapse ≥3cm, disease-free and overall survival.

There were 669 men enrolled from 35 UK centers (2008-2014), with a mean tumor size of 2.9 cm, and 358 (54%) were low risk (≤4cm, no rete testis invasion). In those patients remaining on surveillance, compliance was good with 94% of scans attended, 79% on time (+/- 4 weeks). Median follow-up was 72 months over which 82 (12%) patients relapsed. Incidence of stage ≥IIC relapse was low in all groups (n=10). More events occurred with 3 scans compared to 7 scans, though non-inferior based on design criteria: 9 (2.8%) versus 1 (0.3%), 2.5% increase (90% CI 1.0% to 4.1%; intent-to-treat). In the 3-scan arms 4/9 relapses could potentially have been detected earlier with the 7-scan schedule:


Fewer events occurred with MRI versus CT: 2 (0.6%) versus 8 (2.5%), 1.9% decrease (90% CI -3.5% to -0.3%; intent-to-treat). Incidence of relapse ≥3cm was 3.7% and non-inferiority was shown for both comparisons:

In all groups, most relapses were detected at scheduled imaging, very few occurred beyond 3 years (5 in 558 at risk, <1%):


Relapse treatment outcomes were good (81% complete response) with no tumor-related deaths. Treatment for stage >=IIC was typically BEP x3 or BEP x4, although 16/72 (22%) of patients with lower stage also received BEP. 5-year disease-free survival was 87% and for overall survival 99% and similar across groups.

Dr. Huddart concluded his presentation of TRISST with the following take-home points:

  • Incidence of advanced relapse was very low regardless of imaging modality or frequency
  • Treatment for relapse was successful and long-term outcomes were excellent in all arms, with no deaths due to testicular cancer
  • MRI is non-inferior to CT, avoids irradiation, and should be recommended
  • A 3-scan schedule was non-inferior to 7 scans
  • Relapses beyond 3 years was rare
Presented by: Robert Huddart, MD, PhD, Royal Marsden Hospital and Institute of Cancer Research, United Kingdom

Written by: Zachary Klaassen, MD, MSc – Urologic Oncologist, Assistant Professor of Urology, Georgia Cancer Center, Augusta University/Medical College of Georgia Twitter: @zklaassen_mdduring the 2021 American Society of Clinical Oncology Genitourinary Cancers Symposium (#GU21), February 11th-February 13th, 2021