Comparing F-18 Axumin results with PSA values in patients with prostate cancer

Objectives: For over 30 years Prostate Specific Antigen (PSA) has been the gold standard for finding prostate cancer in early stages and following effectiveness of treatment for patients with prostate cancer. But is it good enough on its own to effectively evaluate disease progression without a F-18 Axumin scan? This research is to determine if there is a correlation between PSA values and Axumin scan results in patients with prostate cancer.

Methods: Data were retrospectively collected and analyzed from 117 consecutive F-18 Axumin scans completed between March and December 2017 at the NorthShore University HealthSystem (NS). A GE Discovery 710 PET/CT scanner, with Time of Flight software was used. Per the manufactures protocol, the patients were injected with 9-12 mCi of F-18 Axumin on the imaging table and immediately had the CT portion of the exam. This was directly followed by the PET acquisition. Patients were scanned mid-thigh to base of skull, acquiring 7-8 bed positions, depending patient’s height. The first 2 bed positions are 5 minutes a position, with the remaining set to 3 minutes per position. For each of the 117 PET scans analyzed a recent PSA value was recorded. 21 of the 117 patients did not have a PSA value available, so they were omitted from the study. PSA values used were obtained using the Roche PSA method, and patients with a value greater than 4.5 ng/mL were considered abnormal. For a negative Axumin scan, patients were reported having normal biodistribution in bone marrow, liver, pancreas, muscles and urinary tract. A positive Axumin scans would be abnormal biodistribution in the bladder, rectum, lungs, lymph nodes, liver, bone, or other body tissues.

Results: Total of 77/96 (80.2%) had a positive Axumin scan and 19/96 (19.8%) had a negative scan. The mean PSA values for the patients with a positive scan were 26.21 ng/mL, with a max of 270ng/mL and minimum of 0.03 ng/mL. The mean for patients with a negative scan was 1.18 ng/mL, with a max of 3.72 ng/mL and minimum of 0.02 ng/mL. A Mann-Whitney U test was performed and gave a value of p<0.0001. This result showed that there was statistical difference between PSA values in a positive and negative PET Axumin scans.

Conclusions: There is a visual difference between the two mean PSA values, and also a statistically significant difference between the PSA values and a positive or negative Axumin scan. Based on these results, a higher PSA value could be used independently to predict the extent of the disease without an Axumin scan. This research would have been helped with a larger sample size, and categorizing patients based on treatments.