The relationships between the total volumes of OARs and the doses they received in the case of EBRT treatment of the prostate cancer

In the case of the external beam radiotherapy (EBRT) treatment of the prostate cancer there exist two categories of toxicity effects: genito-urinary and gastro-intestinal. The main objective of this work is to investigate the relationships between the total volumes of organs at risk (OARs) and the doses they received in the case of the EBRT treatment of prostate cancer. Knowing these relationships it could be possible to reduce the dose contributions to the OARs by increasing or decreasing their volumes by the intake of an amount of a fluid or applying a special diet during the EBRT treatment and, consequently, in such a way to decrease the possibility of appearing of toxicity effects. Through this work the results obtained by analysis of the data collected from dose volume histograms of 30 patients have been presented. The correlations between the doses received by bladder and rectum and theirs volumes have been investigated. We found the strong significant Pearson’s negative correlations, obtained in the case of bladder between D mean and the volume ratios V / V PTV ( r = -0.729 and r = -0.707, p < 0.01) as well as between V 65 and V / V PTV ( r = -0.627 and r = -0.605, p < 0.05). In the case of rectum only significant positive Spearman’s correlation was found between D max and V ( r = 0.524, p < 0.05). The obtained results impose the necessity for monitoring and applying a special and planned diet, as a part of the whole EBRT treatment of prostate cancer in order to ensure the reproducible conditions for OARs.