Conformal hypofractionated and accelerated radiotherapy with cytoprotection (HypoARC) for high risk prostatic carcinoma: rationale, technique and early experience.

Recent radiobiological analysis of the radiotherapy results for prostate cancer revealed that prostate carcinoma behaves as a late responding tissue, sharing an alpha/beta ratio lower than 2Gy. These findings suggest that hypofractionation may be more effective. Reduction of the overall treatment time could further increase response by abrogating the effect of rapid tumor repopulation. In the present study we report a conformal technique applied (to pelvis and prostate) for the treatment of high-risk prostate cancer, using hypofractionated and accelerated radiotherapy (3.4Gy x 15 consecutive fractions) supported with high-dose daily amifostine (1000mg subcutaneously) to protect normal tissues against early and late effects. The biological dose delivered to the prostate cancer by this HypoARC (hypofractionated accelerated radiotherapy with cytoprotection) technique is estimated to be 71.4Gy (alpha/beta= 1.5 Gy). The time-adjusted biological dose is estimated to 77-94 Gy. Amifostine tolerance was excellent. All seven patients recruited up to now have accomplished their treatment with grade 0-1 cystitis or diarrhoea (5/7 grade 0). The study is ongoing to assess efficacy and late effects of HypoARC.