Visual vs. SUV Analysis for Prostate Cancer Imaging

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Neal Shore, MD, FACS: Larry, how do we go about doing the interpretation and helping both our colleagues in radiation oncology and the urologists on the tumor board think seriously?

Lawrence Saperstein, MD: Big questions. I just wanted to make a quick comment on this and reinforce what Mike said. The MIPs – the maximum intensity projection images on the left – are three-dimensional renderings of the dataset, right? In real time, these rotate in a circle. And as Mike said, you can separate the activity in the lymph node from the somewhat tubular look of the ureter in this patient. I also want to point out that the SUV [standardized uptake value], although it can be useful, visual analysis is important for interpretation. And what I mean by that is how does the lesion activity compare to normal structures in the patient? If you can look at the scan, we know there are moderate liver activities. There’s a lot of activity in the kidneys. What is interesting with the PSMA [prostate-specific membrane antigen] agents are the parotid glands. The salivary glands are very hot. And that’s an important benchmark to keep in mind when examining these patients. They’re offered ranking scores, and that’s important if you’re thinking immediate activity that’s higher than liver but lower than parotid or high activity equal to or higher than parotid, those are the lesions we’re concerned about suspected of prostate cancer.

Neal Shore, MD, FACS: That’s a good point. Can you amplify this further? Again, looking at the SUV, uptake in the liver versus its association with positive outcomes. Is there an agreement in the specialty regarding higher or lower absorption in the liver?

Lawrence Saperstein, MD: This experience is changing. But I would say, for the most part, it’s just that the intermediate and high uptake that is greater than the liver or equal to or greater than the parotid, those are the lesions of concern. The SUV I would sometimes take with a grain of salt as it’s a semi-quantitative number. But these are reasonable approaches. And like Mike said, using all the planes, right? The min, max intensity projection is a 3-dimensional rendering. I encourage people to look at the coronal images. And over the years, I’ve learned to appreciate coronal images when looking at lymph nodes and prostate cancer. These are all things to think about.

Michael Gorin, MD: Another thing we often talk about is: does anatomical location make sense for prostate cancer metastasis? In this patient, this node is right at the bifurcation of the internal and external iliac, exactly where you would expect to see lymph node metastasis. And regardless of the value of the SUV, I put more weight on it being a site of disease than if we had found, say, an inguinal lymph node that had that level of uptake.

Lawrence Saperstein, MD: That’s a great point. And what we always talk about is that we don’t read these scans as radiologists in a vacuum. We know the patient population, we know their pre-imaging risk assessment, so we know what we’re looking for. Because there is a lot of variability. And as we do these analyses, we see more and more uptake variants. And we’ll talk about that as we go through the cases. Big point, though.

Transcript edited for clarity.

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