The effect of Lu-177 Pluvicto therapy treatments on PSA levels

Introduction: As medicine progresses, new options for treating and managing prostate cancer have emerged. Pluvicto (Lu-177 vipivotide tetraxetan) is a radiopharmaceutical used to treat patients with prostate specific membrane antigen (PSMA) positive metastatic castration resistant prostate cancer (mCRPC). Pluvicto targets the PSMA biomarkers on the outside of prostate cancer cells and delivers a small amount of radiation to kill the cancer cells. Pluvicto therapy has been shown to decrease prostate specific antigen (PSA) levels by 50% in 46% of patients who receive the treatment who are also utilizing best standards of care. The purpose of this study was to determine the percent change in initial (pre-treatment) PSA values to subsequent PSA values in patients with mCRPC undergoing Pluvicto therapy at Marshfield Medical Center.

Novartis. Efficacy of PLUVICTO. https://www.hcp.novartis.com/products/pluvicto/psma-positive-mcrpc/efficacy/#psa-decline. Accessed February 2023.

Methods: This study retrospectively examined 15 patients, between 58-84 years of age (median age = 71.3 years), receiving one to six Pluvicto therapy treatments over the past 15 months at our facility. Of these, 3 patients expired prior to completing the six treatment therapy course, 3 patients withdrew due to declining health, and only two patients have received all six doses of the treatment. Prior to receiving each treatment, lab values were recorded and evaluated to ensure each patient met the criteria to receive treatment. However, only the PSA levels were analyzed for this study. To determine whether the Pluvicto therapy treatments are contributing to a decrease in PSA, percent change calculations were performed between the initial pre-treatment PSA values and the most recently recorded value. Each patient’s individual PSA percent change per dose was evaluated along with the overall PSA percent change for all patients in the study. A separate overall percent change in PSA was also calculated removing the six patients who had either expired or were no longer seeking treatment.

Results: When comparing the patients’ initial pre-treatment PSA to their most recent value, 9 of the Pluvicto therapy patients saw a decrease in PSA and 4 patients saw an increase, which resulted in an average decrease in PSA of 8%. Excluding the six patients no longer receiving treatments, the average change between initial to most recent PSA revealed a 32% decrease. Individually, 33% of patients indicated a decrease in PSA of 50% or greater. Two patients who received one treatment do not have lab values for comparison.

Conclusions: On average, patients undergoing Pluvicto therapy at MMC had an 8% decrease in PSA values between their initial pre-treatment and post-therapy values. Individually, 5 patients saw a decrease of 50% or greater from their initial PSA value. Due to the small number of participants in this study, we obtained a 50% PSA decrease in 33% of our patients receiving Pluvcito therapy rather than 50% PSA decrease in 46% of patients, as stated in the Pluvicto efficacy information. With three deaths and three withdrawals among the small group of participants, it is likely this treatment option was presented to these patients too late, therefore introducing patients to this therapy earlier may be the key to overall better outcomes.