[Options of hypofractionation of proton boost in locally advanced prostate cancer]

The aim was to evaluate the effectiveness of various fractionation proton boost in the proton-photon radiation therapy of locally advanced prostate cancer. The study included 272 patients with prostate cancer and intermediate-to-high risk of progression. 114 patients received 3-D conformal local irradiation of the prostate by proton beam 220Mev. The focal dose of 28-28,8 SoGy-eq was fed to the prostate for 8, 5 or 3 fractions for 3, 4 or 5.5 Gy-eq, respectively. Given the photon component (44 Gy in 22 fractions to the whole volume of the pelvis), the dose to the prostate was 72.8., 72 and 72SoGr-eq, respectively. In 158 patients in the control group the similar doses to the pelvis were supplemented by local 4-dipole photon irradiation of the prostate to 68-72 Gy in 12-14 fractions of 2 Gy. Acute gastro-intestinal (GI) toxicity maximum, 2 St expression, were found significantly less frequently after the proton-photon therapy: in 54.4% of cases, versus 69.2% in the controls (p <0,01). Differences between acute genito-urinary (GU) toxicity were not observed. The frequency of late GI damage of 2 St. was 3 times less frequently observed in the study group: 10.2% versus 34,8 +/-% in controls. Damages of 3-4 St. were found in 1 patient of the main group and in 2 patients in the control group. GU damages of 2 St. were equally common after the proton-photon or just photon irradiation in 8.3% and 9.1% of patients respectively. Damages of 3-4 St. were diagnosed in 2.8% and 3.8%, respectively (p> 0.05). A 5-year survival without biochemical recurrence was in the study and control groups 60,0 +/- 5,4% and 61,9 +/- 4,4%, and a 9-year survival--45,5 +/- 8,5% and 42,8 +/- 7 1%, respectively (p > 0.05). Thus, precise local irradiation by a proton beam with ROD 3-5.5 Gy-eq. and SOD 28-28,8 Gy-eq supplementing photon irradiation of total small pelvis significantly reduces the severity of early and late post-radiation proctitis but does not reduce the risk of damage to the lower urinary tract and does not influence the anti-tumor treatment effectiveness compared to conventional conformal photon radiotherapy. In this case, the proton boost modes: 8 fractions for 3 Gy, 5 fractions for 4 Gy and 3 fractions for 5.5 Gy does not significantly differ in the level of toxicity.