Prostate-specific antigen bounce after high-dose rate interstitial radiation therapy as monotherapy for prostate cancer

Aim: to evaluate prevalence of prostate-specific antigen (PSA) bounce after high-dose rate interstitial radiation therapy as monotherapy for prostate cancer in two different regimens, and to perform an analysis of possible causes for this phenomenon. Materials and methods: in 2012-2017 one hundred ninety eight prostate cancer patients underwent high-dose rate brachytherapy (HDR-BT) as monotherapy in N.N. Petrov National Medical Research Center of Oncology. Treatment was performed with one of two regimens: two 13 Gy sessions (group I) - 67 (33,8%) patients, and three 11,5 Gy sessions (group II) - 131 (66,2%) patients. Patients were treated using Microselectron device with Oncentra Prostate (Elekta) planning system (192Ir). All patients underwent 1 session of HDR-BT during 1 hospitalization with 1 fraction per I implantation with an average period between fractions being 3 weeks. PSA bounce was defined as PSA elevation to 0.3 ng/ml or above during its progressive decline after treatment completion with subsequent return to baseline (pre-bounce) or even lower values during surveillance or anti-inflammatory therapy...