Is the α/β ratio for prostate tumours really low and does it vary with the level of risk at diagnosis?

To answer the questions: Is the α/β ratio (radiosensitivity to size of dose-per-fraction) really low enough to justify using a few large dose fractions instead of the traditional many small doses? Does this parameter vary with prognostic risk factors? Three large statistical overviews are critiqued, with results for 5,000, 6,000 and 14,000 patients with prostate carcinoma, respectively. These major analyses agree in finding the average α/β ratio to be less than 2 Gy: 1.55, (95% confidence interval=0.46-4.52), 1.4 (0.9-2.2), and the third analysis 1.7 (1.4-2.2) by the ASTRO and 1.6 (1.2-2.2) by Phoenix criteria. All agree that α/β values do not vary significantly with the low, intermediate, high and "all-included" risk factors. The high sensitivity to dose-per-fraction is an intrinsic property of prostate carcinomas and this supports the use of hypo-fractionation to increase the therapeutic gain for these tumours with dose-volume modelling to reduce the risk of late complications in rectum and bladder.