Conformal Radiotherapy (CRT) Alone Versus CRT Combined With HDR BT or Stereotactic Body Radiotherapy for Prostate Cancer

Prostate cancer is considered as a disease with relatively slow natural course and good clinical prognosis. Such description, however, does not well refer to intermediate and high-risk cases where long-term rate of biochemical progression remains not satisfactory, and the available treatment modalities entail a considerable morbidity. Over the last decade several competitive therapeutic approaches have evolved in curative treatment for intermediate and high-risk prostate cancer. The use of intensity-modulated radiation therapy (IMRT) made possible to escalate the total dose to the prostate without excessive toxicity. Based on assumption of low value of low α/β value for adenocarcinoma of prostate, there is a potential of escalating the biological dose to the tumor with higher dose per fraction. High-dose-rate brachytherapy (HDR-BT) is one of the options, with the ability to conform radiation dose to the prostate with sharp dose gradient adjacent to critical organs. An increasing number of studies suggest its usefulness as a boost in intermediate and high risk disease. The randomized trial conducted in UK compared external beam radiotherapy (EBRT) alone with EBRT and HDR brachytherapy as a boost. Combining EBRT with HDR BT - boost resulted in significantly higher relapse-free-survival (RFS) with comparable incidence of severe late toxicity. However, the total dose used in EBRT alone - arm and radiotherapy technique may be considered suboptimal according to current standards. Stereotactic body radiotherapy (SBRT) may be an interesting alternative to HDR brachytherapy, not requiring implantation of multiple catheters and anesthesia. SBRT boost for advanced localized prostate cancer has the potential to reduce toxicity while escalating the dose. First results of trials combining conventional irradiation with hypofractionated stereotactic boost and institutional pilot results gave promising outcome. The comparison of these modalities of radiation therapy for prostate cancer will be performed in the current phase III trial study.