The use of prostate-specific antigen (PSA) for the monitoring of radiation therapy in prostate cancer.

Background: The classic methods for surveilling the efficacy of radiotherapy in prostate cancer are not accurate enough. The objective of this analysis was to determine whether prostate-specific antigen could perform this task.
Materials and Methods: From 1/95 to 10/95, 16 patients were treated at our clinic. 7 of these underwent primary irradiation, 4 treatment for local recurrence, and 5 had adjuvant radiotherapy. Radiotherapy was carried out with a total dose of 60 Gy in 30 fractions, 10 fractions per week, to the prostate bed plus 2 cm safety margin.
Results: PSA levels usually start to decline between the 3rd and the 4th week of radiotherapy with a half-life of 2.5 months. Five patients had equal or rising PSA levels, including all three patients with recurrent tumor.
Discussion: In most cases, PSA declined continuously from the 3rd week of therapy. Our median half-life was similar to other reported results. Persisting or rising PSA levels are an indicator for local or distant recurrence; all our patients who developed a recurrence showed a corresponding PSA increase.