Prostate Cancer Testing
A more recent publication in JAMA (v 294, p440, 2005) specifically considers patients who undergo external beam radiation therapy. Since an increase in PSA of 2 ng/mL per year causes a large increase in prostate cancer mortality despite surgery, this study examines whether the same enhanced risk occurs for patients who undergo radiation therapy. The study took place over a period of 13 years, involving 358 men treated with radiation therapy.
The study finds that patients who experienced a rise of more than 2 ng/mL per year prior to the treatment, had a shorter time to prostate cancer-specific mortality (Risk Ratio of 12, and a Margin of Error between 3 and 54), compared with men who had a lower PSA increase rate. The actual risks differ, based on the T stage and Gleason score. For low risk disease and high PSA increase rate (>2), the seven year prostate cancer mortality rate was 19% (2% to 39% Margin of Error), compared with 0% men who had a low PSA increase rate. For men with a higher risk, the seven year mortality rate was 24% (PSA rate > 2) and 4% (PSA rate <2).
In conclusion, although the errors are large, these results are consistent with the ones from surgery. A PSA increase rate greater than 2 ng/mL is associated with a much higher risk of death due to prostate cancer following radiation therapy or surgery. The researchers suggest that androgen suppression therapy should be used for these cases in combination with the treatment, to enhance the chances for survival.