3D-CRT Versus SIB IMRT Acute Toxicity Outcomes in Preoperative Concurrent Chemo-Radiotherapy for Locally Advanced Rectal Cancer

The primary aim of this study is to compare the acute toxicity profiles between locally advanced rectal cancer (LARC) patients treated with preoperative 3-dimensional conformal radiotherapy (3D-CRT) and simultaneous integrated intensity modulated radiation therapy (SIB-IMRT). 40 patients with LARC were equally divided into 2 groups; arm A received preoperative 3D-CRT concurrent with Capecitabine, while arm B received preoperative SIB-IMRT concurrent with Capecitabine. All patients were seen and evaluated once a week during chemo-radiation and any acute toxicity was recorded. Significantly fewer patients experienced grade 3 genitourinary toxicities in arm B vs arm A with a p-value = 0.048. Regarding grade 2 and grade 3 gastrointestinal toxicities, it was significantly higher in arm A compared to arm B with p-values of 0.043 and 0.021 respectively. There were no statically significant differences between Dmean & Dmax of the urinary bladder (UB) and small bowel (SB) in both techniques. The V45 of the UB was higher significantly in the 3D-CRT plans compared to the SIB-IMRT plans, with a p-value of 0.003. The V45 of SB was higher in the 3D-CRT arm with a p-value of 0.001. The V45 of UB & SB was statistically less in the IMRT plans compared to the 3DCRT plans. This was reflected in the toxicity profile of the patients, grade 2 GU as well as grades 2 & 3 GI toxicities were statistically of lower frequency in the IMRT group compared to the 3DCRT group.