The aim of this study is to evaluate the increase of radiation dose administered in patients diagnosed with locally advanced rectal cancer in terms of ypRC with tolerable toxicity, using IMRT (concomitant boost technique).

The hypothesis that arises is an improvement in the proportion of pathological complete responses, resulting therapeutic gain, as a result of a higher dose of radiation delivered to the tumor volume without incurring a higher gastrointestinal toxicity to the patient or surgical complications later, thanks to the use of intensity modulated radiotherapy (concomitant boost technique) that allows us to significantly reduce the administered dose organs at risk.

Inclusion Criteria:

• Pathologically proven diagnosis of adenocarcinoma of the rectum

• Clinically determined to be stage T3 or T4,N0-N2, and M0 -staged by MRI or transrectal ultrasound of the rectum

• Patients who are medically operable and who have resectable adenocarcinoma of the rectum at least <11cm from the anal verge

• Adequate liver/renal and haematological function.

• Eastern Cooperative Oncology Group (ECOG) performance 0-2

• Age ≥ 18 years

• Full blood count obtained within 2 weeks prior to registration on study, with adequate bone marrow function defined as follows:

  • Absolute neutrophil count (ANC) ≥ 1,800 cells/mm3
  • Platelets ≥ 100,000 cells/mm3
  • Haemoglobin ≥ 8.0 g/dl
  • Serum creatinine within normal institutional limits
  • Bilirubin within normal institutional limits
  • AST and ALT < 2.5 x the IULN

• Patient must sign study specific informed consent prior to study entry

Exclusion Criteria:

• Prior systemic chemotherapy for colorectal cancer; note that prior chemotherapy for a different cancer is allowable.
• Prior radiotherapy to the region of the study cancer that would result in overlap of radiation therapy fields
• Any evidence of distant metastases (M1)
• A synchronous primary colon carcinoma