Comparing PSA and SUVs in PSMA Positive Prostate Cancer for Patients with and without Prostatectomy

Introduction: Piflufolastat is a Positron Emission Tomography (PET) radiopharmaceutical used to find Prostate Specific Membrane Antigen (PSMA) positive prostate cancer. This abstract will look to see if there is any correlation between PSA (Prostate Specific Antigen) values and positive PSMA PET imaging. This retrospective examination of patient data examines trends of patient’s SUVs (Standard Uptake Values) and PSAs for this patient group.

Methods: Data was collected for 121 patients’ and included PSA values taken within 30 days of PET imaging, whether the patient had a prostatectomy or not, and the SUV_MAX. The patient’s PSA values were compared to the SUV_MAX. These values were used to examine incidence of positive scans in two locations: the prostate bed or prostate gland and pelvic lymph nodes. The data collected was compared to determine if there was a correlation between PSA values and SUV_MAX for the sites of interest. If two PSAs were collected within the same number of days the higher value was used.

Results: Patients without their prostate had a lower incidence of having abnormal uptake in the prostate bed. The patients without their prostates had a 16.7% incidence of abnormal uptake in their prostate bed while patients retaining their prostate had a 67.2% incidence of abnormal uptake in their prostate. Those without their prostates had a 50.0% incidence of abnormal uptake in the lymph nodes while patients without their prostates had a 54.1% incidence of abnormal uptake in their lymph nodes. PSA and SUV_MAX were graphed linearly for the prostate or prostate bed and pelvic lymph nodes for patients with their prostates and the same was done for patients without their prostates. The Pearson Correlation Coefficient was used to assess the data.

Conclusions: The data shows that patients with a prostatectomy had a lower overall incidence of recurrence in both the prostate bed and pelvic lymph nodes. The incidence rate for both sites had a marked difference in whether a SUV_MAX was abnormal. The greatest difference was in the prostate bed with a 50.5% higher incidence in patients retaining their prostate than those without. The pelvic lymph nodes had a difference between patients with and without their prostates; however, the difference was only 4.1% higher for patients retaining their prostates. The comparison of PSA and SUV_MAX of the prostate, prostate bed and pelvic lymph nodes showed visual trends with little correlation. The only SUV_MAX which showed a moderate correlation of -0.31 via the Pearson Correlation Coefficient was the comparison of PSA and SUV_MAX examined for patients without their prostate in the prostate bed. This showed an increase of 0.137 SUV_MAX per one point of PSA. This correlation could be due to a smaller sample size since most patients without a prostate had normal values. The correlation for these data sets shows that more data would be needed to assess whether a better correlation exists.