Two new approaches to surveillance imaging after treatment of stage I testicular seminoma sharply reduce or eliminate radiation exposure relative to the standard approach, without substantially compromising relapse detection, the phase 3 TRISST study suggests.
Results were reported at the 2021 Genitourinary Cancers Symposium (Abstract 374).
“Stage I seminoma has a survival that approaches 100%. Over recent years, CT surveillance has become an international standard of care and has largely replaced the use of adjuvant treatment,” said investigator, of The Royal Marsden NHS Foundation Trust, London.
“A typical surveillance protocol, however, consists of multiple CT scans taken over a period of a few years and results in quite a high diagnostic radiation dose, which has raised questions about the long-term risk of second malignancies related to this program,” he noted. “At the moment, there is no evidence base to inform how frequently imaging should be undertaken and the type of imaging that should be used.”
Results of TRISST showed that, with a median 6-year follow-up during which men were monitored with various surveillance protocols, 1.5% experienced a relapse that was advanced (stage IIC or higher) at detection.
The incidence of relapse was 0.3% with the standard schedule of seven abdominal surveillance scans and a statistically noninferior 2.8% with three more widely spaced scans. Also, compared with the standard CT scans, which yielded an incidence of 2.6%, MRI scans were noninferior, yielding an incidence of 0.6%.
“The three-scan schedule was noninferior to seven scans in our protocol, and in fact, with the three-scan schedule, we would use over 1,000 fewer scans at a cost of perhaps having four relapses that could have been avoided,” Dr. Huddart pointed out. “We can conclude that MRI is noninferior to CT and should be recommended to avoid irradiation. This study will provide an evidence base for making the transition to MRI, which is important. The MRI scan is more complex – it takes longer and is more resource heavy. So we do need to supply the evidence that it is the right thing to do for patients.”
Need for expertise in interpreting MRI scans is a valid concern, he acknowledged. “There is a degree of specialization in the UK for testis cancer management, and clearly, you had to be specialist to take part in the study. So I can’t say it is your everyday radiologist, but the data would suggest we actually saw less errors in terms of pickup with the MRI scan than with the CT scan,” he said. “You do need to have a level of expertise, but it doesn’t require super-specialist expertise. I suppose that will be a learning lesson for all of us, to learn better MRI interpretation if we are using MRI.”