Rectal Cancer

Excerpt

Colon and rectal cancers (CRC) combined are the third most commonly diagnosed cancer in the United States and the second deadliest. Rectal cancer has distinct environmental associations and genetic risk factors different from colon cancer. The transformation of the normal rectal epithelium to a dysplastic lesion and eventually an invasive carcinoma requires a combination of genetic mutations, either somatic (acquired) or germline (inherited), over an approximately 10 to 15 year period. Response to pre-operative therapy and pathological staging are the most important prognostic indicators of rectal cancer.

Initial workup starts with a careful history and physical examination, including a digital rectal exam. An endoscopic examination with rigid sigmoidoscopy is required; this is important to measure the distance from the lesion to the anal verge and for tissue biopsy to confirm rectal cancer. Once rectal cancer has been established pathologically, an MRI or transrectal ultrasound can accurately determine local tumor extension and node status. Baseline computed tomography of the chest, abdomen, and pelvis rules out metastatic lesions. An interdisciplinary evaluation by medical oncology, radiation oncology, and surgical oncology is important to discuss the best combination of perioperative chemo-radiotherapy (in addition to possible surgical resection) that could augment the chance of cure, particularly in high-risk patients. Oligo-metastatic disease to the liver and lung and local-recurrence patients with rectal cancer are still 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.