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2018 Congress of the Mexican Association of Oncological Urology

Will Molecular Imaging Change Advanced Prostate Cancer Staging?

Acapulco, GRO, Mexico (UroToday.com) From a surgeons perspective. The role of modern radical prostatectomy is to achieve complete excision of cancer with preservation of function. But prostate cancer is a microscopic disease, so we cant see the margins during surgery and decision making is based on preop information. Depending on this information, different surgeons would perform different techniques, partial vs complete neuropreservation for example. On the other hand, we know that postitive surgical margins affect prognosis, therefore the importance of performing a complete resection has a huge impact. MRI has helped us obtain preop visualization of the disease, it helps to determine if there is extraprostatic involvement for example. However in some cases, the precise extent of the disease cant be determined. We need other tools to allow us to better guide the surgeon.

The same happens with lymph nodes, the best template is extended template, but we know that we will still miss 35% of landing sites. Molecular imaging appears to give us a better understanding and accuracy regarding this problem.

PSMA is the most important molecule in prostate cancer, an excellent target for imaging, and currently the most popular.

However, when it comes to lymph nodes, its accuracy depends on the size of the LN and how we define positivity. For example with a cut off of 2 SUVmax there is a specificity of 95% and sensibility of 87%. If we use a cut off of 1.5 SUVmax, we increase detection of positive LN detection but also of false positives. When it comes to size, PSMA doesn´t detect lesions of less than 2mm., it detects 60% of lesions between 2-4mm and 86% of 5 mm or more.

Molecular

An example was presented, of a man with prostate cancer, after resection and he presented elevation of PSA after surgery. A PET-scan was performed and recurrence in the bulbar urethra was detected, the lesion was biopsied and reported prostate cancer, it was resected.

it is important to mention that PSMA performance is not that good with PSA lower than 0.5ng/dL. It improves with higher values. New technology is being used and there is promising research regarding intraoperative imaging, with nanoparticles, in open and laparoscopic surgery, after completing the prostatectomy, to assess for residual disease.

Presented by: Karim Touijer, MD

Written by: Paulina Bueno Garcia Reyes, MD, medical writer for UroToday.com and Ashish Kamat, MD, Professor of Urology and Director of Urologic Oncology Fellowship at M.D. Anderson Cancer Center, at the Mexican Urologic Oncology Association Meeting - July 26 - 28, 2018