Dynamics of Radiation Toxicity after Hypofractionation Proton-X-Ray, or Conformal X-Ray only Radiotherapy in Locally Advanced Prostate Cancer
The purpose to evaluate the dynamics and prognostic factors of acute and late toxicity after different variants hypofractionation proton boost - photon vs. traditional conformal photon only irradiation for locally advanced prostate cancer. This investigation involves 272 patients with high and intermediate progression risk. 114 patients received 3D conformal local treatment of prostate with the use of a 220 MeV passively scattered proton beam and a special rectal marker - endostate under requirement of portal visualization. Taking into account the photon component (44 Gy at 22 fractions for the whole volume of the small pelvis), the dose for prostate amounted to 72.7 and 72.0 Gy (RBE), respectively. 158 patients in the control group received, ad- ditionally to the similar doses to the small pelvis, the local 4-field 68.0-72.0 Gy photon irradiation of the prostate. An acute gas- tro-intestinal (GI) toxicity of the maximal grade 2 intensity (RTOG/EORTC) was occurred reliably rarely after the proton - photon therapy: in 54.4 % cases against 69.2 % in the control group (p<0.01). In spite of the proportion of patients who had grade 1-2 GI or GU toxicity was reduction in 30 % and 15 %, respectively, during 10 year after treatment, the cummulative risk of grade 3-4 GU injuries increased to 9 % of cases. The precise local proton beam treatment with the fractional dose 3-5.5 Gy (RBE) and with the total dose 28.0-28.8 Gy (RBE) as a boost to the photon treatment of the whole volume of pelvis reliably re- duces the intensity of acute and late post-irradiation rectitis, but does not cut the risk of the low urinary tracts, and does not influ- ence the anti-tumor efficacy of the treatment as compared to the traditional conformal photon radiation therapy.