Colorectal cancer (CRC) is the third leading cause of cancer related death worldwide . It is becoming increasingly important to identify prognostic and predictive markers for rectal cancer. Surgical resection remains the definitive treatment for CRC. However, rectal cancers are more challenging to resect than their colonic counterparts due to limited access within the pelvic space, as well as close proximity to the mesorectal fascia and pelvic organs. As a result, patients with rectal cancer consistently suffer from inferior survival outcomes relative to colon cancer patients . Preoperative radiotherapy aims to downstage the primary tumor, eradicate microscopic disease, and reduce recurrence rates [3–5]. Unfortunately, tumor response to radiotherapy varies between individuals, even after adjusting for clinico-histopathological variables. Tumor down staging following preoperative radiotherapy occurs in approximately 60% of patients, but only 10–30% will display a complete response  . The availability of a predictive marker of radiation sensitivity would enable selective administration of therapy to those most likely to respond.