3. Being the chi-square value 11.07 for 5 degrees of freedom and a 5% significance level, it cannot be rejected the JQ1 ic50 hypothesis that the fit is acceptable. NTCP values have been recalculated for the

two arms with the optimized parameters; the values of clinical incidence fall now inside the confidence intervals of NTCP, as shown in Table 3. Table 3 Clinical incidence of ≥ G2 late toxicity and NTCP calculations   A B Clinical incidence 14.0% 12.3% NTCP (prior to optimization) TD50 = 80 Gy, α/β = 3 Gy 10 ± 3% 6 ± 2% NTCP (after optimization) TD50 = 76 Gy, α/β = 2.3 Gy 15 ± 5% 12 ± 4% Discussion In this work, a modeling of late rectal toxicity in patients with localized prostate cancer was performed. The patients were randomly assigned to receive 80 Gy in 40 fractions over 8 weeks Selleck GSK2245840 (arm A) or 62 Gy in 20 fractions over 5 weeks to the prostate (arm B). The comparison between the conventional and the hypofractionated arms allowed Linsitinib concentration to evaluate the response of rectal toxicity to changes in fractionation. The crude rate of ≥ G2 late rectal toxicity were 14.0% and 12.3% for arm A and B respectively, thus very close to the actuarial values at 30 months (Fig. 3), indicating that this time can be considered

adequate to report the late rectal toxicity, as documented also by other studies [18, 22, 23]. The comparable toxicity rates observed in the two arms suggest that the hypofractionated regimes in prostate cancer are feasible, as previously reported in other studies [24–29], though using different fractionation schemes Dichloromethane dehalogenase and end point definitions. Lukka et al. [24] compared two fractionation schemes

for patients with localized prostate cancer, in a randomized trial designed to give 66 in 33 fractions or 52.5 Gy in 20 fractions to the prostate. The authors reported similar ≥ G3 late rectal toxicity incidence in both arms (1.3%), with a long median follow-up time of 5.7 years. Livsey et al. [26] also analyzed bowel toxicity in hypofractionated regime, giving to the prostate 50 Gy in 16 fractions. The reported ≥ G2 bowel toxicity was lower (5%), presumably due to the consistently lower total dose. Among all studies, the present work is best comparable to the study of Faria et al. [29], who analyzed late rectal toxicity in prostate cancer patients receiving 66 Gy in 22 fractions. They reported a crude incidence of ≥ G2 late rectal toxicity of 18%, with a median follow-up time of 30 months. The deviation from our rate of toxicity probably arise from the different total dose (66 against 62 Gy). Assuming to prescribe to our patients of arm B 66 Gy in 22 fractions to the PTV, with the same relative dose distribution to the rectal wall, the average NTCP would result 17.5 ± 4.8% with our best-fit parameters.