Long-Term ADT Affects PSMA Scans

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?

https://www.ncbi.nlm.nih.gov/pubmed/29980832

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.