Prediction of toxicities of prostate cancer radiotherapy.

We treated a cohort of 116 patients with prostate cancer with three-dimensional conformal hypofractionated radiotherapy to a total dose of 52.8 Gy in 16 fractions (3.3 Gy per fraction). The correlation between acute and late gastrointestinal (GI) and genitourinary (GU) toxicity and dose-volume parameters was analysed.

Comparison of observed incidence of toxicity and normal tissue complication probability calculated from dose-volume histograms (DVH) of all patients using radiobiological Lyman-Kutcher-Burman model was performed. The results of our study suggest that acute gastrointestinal toxicity ≥ grade 2 (G2) is the significant predictor of late toxicity ≥ G2 (p=0. 006). Observed incidence of acute and late GI toxicities ≥ G2 was 9. 7% and 11. 5%, respectively. NTCPs of acute and late GI complications ≥ G2 were 11. 3% and 2. 5%. Observed incidence of late GU toxicity ≥ G2 was 14. 2%, NTCP was 0. 8%. Comparison of calculated probability of acute GI toxicity ≥ G2 and observed incidence indicates that parameters of radiobiological models are set appropriately. Comparison of observed incidence of late GI and GU complications ≥ G2 and calculated NTCPs shows the need of refinement of LKB model parameters for acute and late GI and GU complications ≥ G2.   Keywords: prostate cancer, radiotherapy, acute and late toxicity, radiobiological modeling.

Neoplasma. 2015 Dec 07 [Epub ahead of print]

B Hostova, P Matula, P Dubinsky