EAU 2021 | TRISST: MRI versus FDG-PET-CT for the treatment of testicular cancer

Yeah. So, my name is Tahlita Zuiverloon and I’m one of the urologists at the Erasmus MC Center for Complex Retroperitoneal Surgery, with a focus on testicular cancer. And during the EAU from this year, I mainly focus on the role of imaging in testicular tumors. And to give it a little bit of background or context… So, imaging for testicular cancer can be used in different settings. First of all, we can start at the initial diagnosis. And secondly, we can use imaging for the surveillance of these patients, but also in the post-chemotherapy setting to detect residual disease.

And one of the most important things that was presented at ASCO GU this year by the group from Robert Huddart was the trial of imaging and surveillance in a stage I seminoma testicular tumors. So, in this study, what we discussed was that they looked at CT versus MRI and the number of CTs or MRIs, and whether this could be safely reduced with an acceptable increase of advanced relapses.

So there were two groups where the patients, first of all, received CT versus MRI and within the CT or MRI arm, they received either three or seven images. So, either by CT or by MRI. So, we included 669 men with stage I seminomas and of these patients 82 relapsed. And 10 out of these 82, so 12%, had an advanced relapse.

So, the first thing that they discussed was whether the MRI was inferior to the, non-inferior to the CT, and based on their non-inferiority criteria, they found that the MRI is non-inferior to the CT. Secondly, they show that having three scans is non-inferior to seven scans. So, they concluded that if it’s feasible, an MRI is a very good alternative for the CT. And in this way, we can also reduce the toxicity on our testicular cancer patients and to reduce also the number of secondary malignancies.

Other things that they also found in the TRISST trial is that there is a low rate of advanced relapses, and also, after three years, relapses are rare. So, in the discussion, what we talked about was, I received a question if I would advise to use the MRI and how we would go about this in areas where the MRI is not available. So, what I think is important for the future is to consider that the MRI from the trial is non-inferior to the CT. And most of all, when MRI is not used, this is because of cost effectiveness, because of the lack of expertise to evaluate the MRI, and also the organizational implementation, that’s very difficult, but we should think about whether these reasons are good enough for us to withhold the MRI from our patients, since we have the results from the TRISST trial.

So in my opinion, I think it’s very important that if there is a possibility to use the MRI, we should use it for our patients. And if the MRI is not available, then we should use the CT, but with less frequent imaging. So, that was the first part that we talked about on imaging in testicular tumors.

Secondly, we talked about the role of imaging. So, the PET CT in the post-chemotherapy setting. And I think there was a general consensus, which has been unchanged over the past years, that in case of a residual mass that is larger than three centimeters, we should use the PET CT in case of seminomas because of the high, negative predictive value. But in contrary, in case of non-seminomas there are two landmark papers that we discussed that show that the positive predictive value of the PET CT for non-seminomas, is approximately 50%. Sorry, the negative predictive value is approximately 50%. So, this means it’s like flipping a coin. And therefore, I think the general consensus is still that there is no role for PET CTs in the post-chemotherapy setting in non-seminomas.

So, in the end, we had a wrap-up where we talked about the future of imaging for the testicular tumors, and also specifically about the role of the PET CT for non-seminomas. And some latest manuscripts showed that there might be a role for the PET CT if we have a look at the kinetic rate or the standard uptake value in non-seminomas, because what they saw in these studies is that for example, in teratomas the kinetic rates, or the uptake of the tracer, is quicker compared to, for example, scar or necrosis. So, this is really worthwhile investigating in future studies.

And the second thing that I think is also important considering, is lymphotropic nanoparticle-enhanced MRIs, where the nanoparticles are taken up by macrophages within the lymph nodes, and this increases or actually improves imaging of the lymph nodes.

And lastly, what I think is important for the future is radiomics in detection of testicular cancer. As there have been a few recent studies also presented in abstracts, where they show that detection of tumor versus normal tissue by radiomics and deep learning algorithms is also feasible. And also, to distinguish between seminomas and non-seminomas is feasible by using radiomics. So, I think this is also really something we should keep in mind for future research.