Newer and more sensitive scans have become commonplace for both uses of prostate cancer diagnosis and treatment decision making. One of the more commonly used new scans is PSMA PET/CT with 68 Ga-PSMA-11.
In preclinical studies, it has been found that short-term androgen deprivation therapy (ADT) can significantly increase PSMA expression on PC cells. Additionally, retrospective clinical data in large cohorts suggest a positive association between long-term ADT and a pathological PSMA PET/CT scan.
A retrospective analysis was performed of all 1,704 men who underwent a 68 Ga-PSMA-11 PET/CT scan study in one institution between the years of 2011 and 2017. The study analyzed the influence of long-term ADT on PSMA PET/CT findings.
They found that they visualized 31 prostate caner lesions in ten men before they started ADT. During ongoing ADT (duration of 42 to 369 days with a median of 230 days), only 14 lesions were visible in eight of the ten men. They also observed that average tracer uptake values decreased in 71% and increased in 12.9% of the prostate cancer lesions. Of all lesions, 33.3% were still visible in six men with a complete PSA response (≤0.1 ng/ml).
Conclusion: Continuous long-term ADT significantly reduces the sensitivity and visibility of castration-sensitive prostate cancer on PSMA PET/CT scans. Since the objective is to visualize the maximum number of lesions men should not start ADT before having a PSMA PET/CT.
This study only speaks to the sensitivity of a PSMA PET/CT scan in castrate sensitive prostate cancer; it does not have any relevance to men who are castrate resistant. Additional studies are needed to answer the question, does ADT effect PSMA PET/CT scan results in men who are castrate resistant?
Joel T. Nowak, MA, MSW wrote this Post. Joel is the CEO/Executive Director of Cancer ABCs. He is a Cancer Thriver diagnosed with five primary cancers - Thyroid, Metastatic Prostate, Renal, Melanoma, and the rare cancer Appendiceal cancer.