ABSTRACT
Complications of pelvic irradiation have gained more attention because of increased survival of patients. CO-60 Teletherapy has wide penumbra in comparison with linear accelerator that can cause testes irradiation during radiotherapy in vicinity of lower border of pelvic portal when treated for rectal cancer. In this study we compared testicular doses of testes when pelvis is irradiated for rectal cancer and its effect on sex hormone levels. In a cohort study, rectal cancer patients treated by pelvic irradiation concomitant with chemotherapy in two group. A group treated by Co-60 Teletherapy and another group by Linear Accelerator [LINAC]. Sex hormones serum levels were measured immediately before and 3 to 6 weeks after finishing irradiation. Testicular doses were measured by TLD [LiF], 3 times during whole course of irradiation in 5 patients of each group. T test and Mann-Whitney were used to compare data. 28 patients entered in study but 2 patients died early in course of radiotherapy [1 in each group], and one patient excluded because testes was inside of treatment portals. Patients and disease characteristics were similar between groups. Testes doses in patients treated by LINAC [55 +/- 24.7 mGy] was significantly lower than Co-60 [120 +/- 23 mGy] [p <0.001]. FSH and LH serumic level increased after irradiation in both groups and there is not a relation between FSH and LH levels with treatment machine [p<0.2] for LINAC and p<0.6 for Co-60. Decrease in serumic levels of testosterone was significant in patients treated by CO-60 [p<0.05], but was not significant in LINAC group [p<0.3]. It seems using LINAC in treating patient with rectal cancer can decrease testes doses but can not prevent hormonal changes. We suggest extra shield to decrease testes doses below the toxic dose