ABSTRACT

Brachytherapy of localized prostate cancer is implemented mainly in two different dose rates, being Low Dose Rate (LDR) and High Dose Rate (HDR). The α/β ratio of prostate cancer cells, although controversial, is predicted by invio and invitro experiments to be ≤3. This characteristic provides a theoretical advantage in favor of HDR brachytherapy in the treatment of prostate cancer. Whereas for LDR monotherapy which clinical experience is of long standing, 1 to 4 month elapsed time needed to reach total treatment dose due to low radioactivity of the sources and their low average photon energies make this treatment mode less effective radiobiologically, partially caused by low proliferation capacity of prostate cancer. HDR brachytherapy is more often used for high-risk patients as a boost treatment combined with external beam radiotherapy. On the other hand, the necessity of more than one implantation in contrast to LDR brachytherapy and high doses per fraction constitutes a disadvantage for HDR monotherapy against the normal tissue complication probability, even though lower total dose is required. Due to limited clinical experience, HDR monotherapy is not recommended except in controlled clinical trials. The aim of this review is to summarize radiobiologic essentials of brachytherapy practice in the treatment of prostate cancer.