Retrospective Evaluation of PET/CT Scans of Intermediate Risk Prostate Cancer Patients

Abstract

Prostate cancer has a high incidence rate. Research into predictive factors for reoccurrence of prostate cancer can improve patient care and improve mortality rates. A clinical trial at the Cross Cancer Institute, aimed to determine if PET/CT scans using the radioactive tracer 11C choline can predict the treatment outcome of intermediate to high risk prostate cancer patients. 30 patients were enrolled in the clinical trial, of which 25 continued on to successful data acquisition. After a baseline scan, treatment occurred over the next 7-8 weeks and patients were followed for up to 5 years. Chosen treatment outcome markers were the most recent PSA (prostate specific antigen) level and biochemical failure (PSA >2 over nadir). Quantitative PET data (standard uptake value – SUV) from interprostatic lesions was exported into Excel in the form of a time activity curves. A computer code, written in VBA (visual basic for applications), was used to sort, group, calculate and graph several parameters and values from patient data. Charts were visually inspected for correlation between any parameter and treatment outcome. Some separation was observed between high and low most recent PSA values and maximum SUV after 40 minute uptake time. Biochemical failure shows some correlation with integral SUV mean. Further evaluation of statistical power is required to determine significance. Biochemical failure occurred in only 4 patients during the 5 year follow-up period, thus limiting these findings. Furthermore, patient withdrawal during the trial limits statistical significance of later time points.