ESTRO 2025 - Abstract Book

S1933

Clinical - Urology

ESTRO 2025

The incidence of reported toxicity was 21% (16 out of 76 patients) and 9.68% (6 out of 62) in mHypo and standard group respectively. RAP [cc] volume parameter mean differences were 6.56 ± 3.9 cc and 8.3 ± 3.8 cc for standard and mHypo group respectively. The result is statistically significant (p<0.01) in respect to the two-sided t-Welch test. Mean DVH and mean differences between values can be found of fig.1. Green circles represent statistically significant results (p<0.01) in respect to the two-sided t-Welch test. Graphs of RAP parameter against irradiated volumes can be found on fig.2. It can be noticed that all points that lies above mean line that are in bleeders’ group are also in mHypo group (blue dots with green circle). For V75Gy graph there can be clearly seen that in general most of the points above mean line are from mHypo group (blue dots). Conclusion: Geometrical plan-related parameters combined with selected dose volumes (fe. Used in this article RAP [cc] with V65-75Gy) can be used as at least indicators maybe as a predictor for rectal bleeding in prostate cancer patients. It can be seen as a step for direct and simple incorporation of clinical results into planning routine. References: [1] Bae, B.K., Kim, J.E., Pyo, H. et al. Long-term findings of rectal endoscopy and rectal bleeding after moderately hypofractionated, intensity-modulated radiotherapy for prostate cancer. Sci Rep 13, 22099 (2023). https://doi.org/10.1038/s41598-023-43202-x [2] Laterza, L., Cecinato, P., Guido, A., Mussetto, A., & Fuccio, L. (2013). Management of radiation-induced rectal bleeding. Current gastroenterology reports , 15 (11), 355. https://doi.org/10.1007/s11894-013-0355-z [3] Withers HR, Thames HD Jr., Peters LJ. A new isoeffect curve for change in dose per fraction. Radiother Oncol 1983; 1:187-191. Keywords: hypofractionation, toxicity indicator