Assessing Ga-68-PSMA PET/CT as a Biomarker in Prostate Cancer

A study aimed to assess the utility of Ga-68 PSMA positron emission tomography (PET)/computed tomography (CT)-based response to neoadjuvant androgen deprivation therapy (ADT) as a possible predictive biomarker in patients with node-positive prostate cancer treated with radiotherapy. The results were presented at the 2022 American Society for Radiation Oncology Annual Meeting.

In this study, presenting author Vedang Murthy, MD, and colleagues analyzed 93 patients with newly diagnosed nonmetastatic prostate cancer with regional nodal involvement as indicated by Ga-68-PSMA PET/CT scan. The population of interest was administered neoadjuvant ADT and treated with image-guided radiotherapy with long-term ADT. The average duration of neoadjuvant ADT was 6 months.

According to the results, a complete Ga-68-PSMA PET/CT-based response was observed in 62% patients for pelvic nodes and 7% for prostate. The researchers noted that a partial response was observed in 23% for pelvic nodes and 55% for prostate, while stable disease was observed in 11% and 18% for pelvic nodes and prostate, respectively. Additionally, progressive disease was observed in 4% for pelvic nodes and 14% for prostate. “Both the absolute and the relative decline in SUV_max for pelvic nodes showed statistically significant association with [biochemical failure] posttreatment using logistic regression (P=.05 each),” the researchers said of the results.

The investigators concluded, “A steeper decline in absolute and relative nodal SUV_max on Ga-68-PSMA PET/CT with neoadjuvant ADT is associated with lower probability of [biochemical failure] postradiotherapy in node positive prostate cancer.”

Source: Mehta PS, Mohite A, Maitre P, et al. Predictive value of Ga68-PSMA PETCT-based response to neoadjuvant androgen deprivation therapy in node positive prostate cancer treated with radical radiotherapy. Abstract 223. Presented at the 2022 ASTRO Annual Meeting; October 23-26, 2022; San Antonio, TX.