The goal of this prospective phase II study was to determine whether personalized planning-based nCRT for LARC would indeed decrease small bowel dose, and whether selected plans, specifically prioritizing lower dose to small bowel, would result in lower rates of acute GI toxicity compared with previously reported rates.

The standard of care for locally advanced rectal cancer is neoadjuvant chemoradiotherapy. However, acute gastrointestinal (GI) toxicity is common. Some retrospective studies suggested that Intensity Modulated Radiation Therapy( IMRT) reduces acute bowel toxicity compere to 3D conformal radiotherapy (3DCRT).The aim of this prospective phase II study to determine whether the use of IMRT planning in neoadjuvant chemoradiotherapy in patients with locally advanced rectal cancer can decrease small bowel irradiation dose compared to commonly used 3D conformal techniques ,and the rate of acute GI toxicity.

Patients (pts) with clinical stage II-III rectal adenocarcinoma were enrolled in a prospective phase II study of preoperative chemoradiation. For each patient two radiation plans were performed: IMRT and 3DCRT. After comparing two DVH (dose volume histogram) plans for organs at risk (OARs), such as small bowel and bladder, pts were treated according to the plan with maximal critical organs sparing. All Patients received 45 Gy in 25 fractions to the rectum and draining lymph nodes, followed by boost to the tumor, with concurrent capecitabine or 5- Fluorouracil .Weekly follow up was performed to assess acute toxicity.

The investigators hypothesize that the use of IMRT in neoadjuvant chemoradiation for locally advanced rectal cancer may reduce the small bowel and bladder irradiated volume and consequently reduce acute toxicity.

Inclusion Criteria:

• Patients with locally advanced rectal adenocarcinoma
• Performance status of 0-2
• Adequate hematologic, renal, and hepatic function

Exclusion Criteria:

• Prior radiotherapy to pelvis
• Metastatic disease at diagnosis