Secondary cancer risk estimation following prostate cancer radiotherapy through gEUD concept and NCRP-116 recommendations

Radiotherapy is one of the practical modalities in prostate cancer treatment, but there is a risk of developing secondary cancers caused by unintended radiation inside the non-target organs. The current study aimed to evaluate the risk of secondary cancer development in organs at risk (the bladder and rectum) following prostate cancer radiotherapy.

A group of 39 patients with prostate cancer who were treated with 3-dimensional conformal radiotherapy (3D-CRT) were enrolled. A dose-volume histogram (DVH) corresponding to each patient was utilized to estimate the absorbed dose for the rectum and bladder and to calculate their respective generalized equivalent uniform dose (gEUD). Finally, the risk of secondary malignancies was estimated by employing the gEUD values and recommended risk factors by the National Council on Radiation Protection and Measurements (NCRP) 116.

The gEUD values for the rectum and bladder ranged from 50–75 and 25-80, respectively. The mean gEUD values for the rectum and bladder were correspondingly equal to 60.97 Sv and 53.74 Sv, respectively. The mean secondary cancer risk (SCR) value for the rectum was 30.4%, while about 16.1% was estimated for the bladder. The estimated SCR in the rectum was 1.88 times higher than in the bladder.

The rectum is more exposed to radiation and is endangered by the development of secondary cancer following prostate cancer radiotherapy. Nevertheless, the probability of cancer incidence in the bladder was also considerable.