Abstract
Objective: High-dose radiotherapy (RT) in prostate cancer has a high local control rate. Generally, the normal tissue toxicity of high doses is overlooked. We aimed to evaluate the rectal volume, diameter, and related dosimetric evaluation that may cause acute gastrointestinal (GIS) side effects in prostate cancer that we treated with intensity-modulated radiotherapy (IMRT).
Method: Seventy-nine patients we treated with definitive or postoperative IMRT were evaluated for acute GIS toxicity according to Radiation Therapy Oncology Group (RTOG) toxicity criteria. The presence of acute GIS side effects and dosimetric parameters including grade and rectal volume and diameter were evaluated.
Results: Seventy-nine patients treated with IMRT were evaluated. Acute GIS toxicity was observed in 21 (26.6%) patients after RT, Grade II side effects were observed in 7 (8.8%), and grade I acute side effects were observed in 14 (17.6%). Grade III and IV toxicity was not observed in any of the cases. No significant correlation was found between the grade of acute GIS side effects and the rectum values of V75, V65, V40, and V30 in dose-volume histograms (DVH), respectively, and rectal volume (cm3) and largest diameter (cm) measurements (p>0,05). The D median for definitive RT of PTV was 78 Gy, and the D median was 66 Gy for postoperative RT. No significant correlation was found between the occurrence of acute GIS side effects and grade of definitive or postoperative radiotherapy (p values, respectively, p=0.693, p=0.307). No significant correlation was found between the widest rectal diameter of less than 5 cm in planning and acute GIS side effects and acute GIS side effects Grade I (p=0.414, p=0.546).
Conclusions: Prostate cancer treatment with IMRT had low rates of acute GIS toxicity. According to our study, the occurrence of acute GIS side effects was independent of rectal volume, diameter, and dosimetric parameters.