Prostate-Specific Antigen Kinetics After Brachytherapy or External Beam Radiotherapy and Neoadjuvant Hormonal Therapy

Abstract

Objectives To characterize the kinetics of prostate-specific antigen (PSA) after radiotherapy (RT) and neoadjuvant hormonal therapy (NHT) for localized prostate cancer. Methods The PSA kinetics of 75 consecutive patients who had undergone RT and NHT (median time 4 months) were followed up for a minimum of 24 months after treatment. RT included a permanent iodine-125 implant (n = 29), a temporary iridium-192 implant as a boost to external beam RT (n = 21), and sole external beam RT (n = 25). A median number of 11 PSA levels per patient were analyzed. Results After a first nadir (median level 0.1 ng/mL 3 months after RT), rising PSA levels were found in 83% of patients and progressively rising PSA levels until the end of follow-up or salvage hormonal therapy for 21% of patients. The PSA levels dropped again after one (23%), two (21%), or more (17%) consecutive increases up to a median level of 0.6 ng/mL (median time 16 months after RT), so that a nadir of 0.1 ng/mL was reached for a second time (median time 35 months after RT). A first nadir of less than 0.1 ng/mL, a PSA increase of less than 1 ng/mL, and a longer PSA doubling time (median time 10 months) were strongly predictive for long-term biochemical control. Conclusions Temporarily rising PSA levels can be expected for most patients after primary RT and NHT following a first nadir. The increasing effects of testosterone owing to NHT withdrawal have a stronger effect than RT in the first months after treatment.