Cancer, Rectal (Rectum)

Colon and rectal cancer (CRC) combined is the third most commonly diagnosed cancer and the second deadliest in the United States. Rectal cancer has distinct environmental associations and genetic risk factors different from colon cancer. The incidence of new cases and mortality of rectal cancer has been steadily declining for the past years, although noticed to rise in recent years on younger adults (less than 50 years). The transformation of the normal rectal epithelium to a dysplastic lesion and eventually an invasive carcinoma requires an accumulation of genetic mutations either somatic (acquired) and/or germline (inherited) in approximately 10 to 15 years period. Tumor regression grade after pre-operative therapy and pathological staging are the most important prognostic indicators of rectal cancer. All newly diagnosed patients with rectal cancer should be universally screened for DNA mismatch repair/microsatellite status that is present in up to 13% of all sporadic rectal cancer cases. A careful history and physical examination, including a digital rectal exam, are paramount on clinical suspicion. An endoscopy examination with rigid sigmoidoscopy is required to measure the distance from the lesion to the anal verge (less than 15 cm) and for tissue biopsy for pathological confirmation of rectal cancer. Baseline computed tomography of the chest, abdomen, and pelvis may initially grossly rule out metastatic stage. Nevertheless, a combined approach by magnetic resonance imaging or transrectal ultrasound will accurately determine tumor extension and node status of the local rectal disease at diagnosis. An interprofessional evaluation by medical oncology, radiation oncology, and surgical oncology should discuss the best peri-operative chemo-radiotherapy route that could augment the chance of cure on high-risk patients. Oligo-metastatic, liver and lung, and local-recurrence patients with rectal cancer are potentially curable with multimodality therapies. Palliative systemic therapy is reserved for non-surgical candidates to ameliorate symptoms, improve quality of life and prolong life expectancy. [1][2][3][4]