Byline: Evrim. Duman, Yilmaz. Bilek, Gokay. Ceyran
Purpose: To evaluate the target volume (TV) and critical organ doses with priority of testes with the comparison of conformal radiotherapy (CRT), dynamic intensity-modulated radiotherapy (DIMRT), and volumetric modulated arc therapy (VMAT) techniques. Materials and Methods: CRT, DIMRT, and VMAT techniques were generated on computed tomography images in prone position of 10 male patients with distal rectal cancer. Conformity index (CI), heterogeneity index (HI), treatment time, and monitor units were examined; dose-volume-histograms (DVHs) for the TV and the organs at risk (OARs) were evaluated. Results: Target dose coverage of all treatment plans was similar. HI and CI values for DIMRT and VMAT were closer to '1' compared to CRT. DVH parameters for OARs were decreased with DIMRT and VMAT compared to CRT. The percent volume (V[sub]x) of 3 Gy dose of testes was 62.01% ([+ or -]25.45%), 42.68% ([+ or -]16.42%), and 35.89% ([+ or -]14.97%) in the CRT, DIMRT, and VMAT techniques, respectively. V[sub]3 of testes decreased with VMAT compared to CRT and DIMRT (P = 0.008 and P = 0.051, respectively). Conclusion: Modern radiotherapy techniques are superior to conformal techniques in planning quality parameters and sparing OARs. DIMRT and VMAT could be considered instead of CRT in the desire to preserve fertility of patients with rectal cancer.
Colorectal cancer is the third most commonly diagnosed cancer, with a 10.9% worldwide incidence per year in males. Rectal cancers constitute approximately one-third of all colorectal cancers, and the cumulative incidence risk of a male for rectal cancer is 1.2% from birth to 74 years.,
The primary treatment for a potential curative disease is surgery, and the addition of radiotherapy and chemotherapy improves the local control rates in patients with a risk of local recurrence. Neoadjuvant chemoradiotherapy before surgery has become the standard treatment in patients with locally advanced rectal cancer. Neoadjuvant chemoradiotherapy often reduces the local recurrence risk of resectable tumors, downstages the tumor, and improves resectability in most of the unresectable tumors.,
Radiotherapy is currently recommended for many patients, and long-term survival after modern multimodal treatment is expected in at least 60% of patients with rectal cancer. Although the most common side effect related to radiotherapy is intestinal toxicity, sexual dysfunction is one of the problems encountered, especially during prolonged survival.,,,,, Lower serum testosterone and lower calculated free-testosterone values have been reported in patients who have been irradiated.
Testicular function loss is especially prevalent in distal rectum tumors due to proximity of the testes to the radiotherapy treatment area. The testes are outside the target radiation volume in most patients, but they can still be exposed to scattered radiation. Although radiotherapy-induced testicular damage is related to the testicular dose of irradiation, the radiation dose limit for the testis has not been clearly defined., The germinal epithelium of the testis is very sensitive to radiation-induced damage, and the changes in spermatogonia occur after as little as 0.1 Gy. The number of spermatogonia reduces progressively over 21 weeks to their minimum levels after...