Cancer of the Rectum
Summary of Key Points
Incidence
• Approximately 40,000 new cases of rectal cancer are diagnosed in the United States annually.
• Since 1998, the incidence rate has been decreasing by 2% to 3% per year.
• The peak incidence of rectal cancer is during the fifth decade of life.
• Aspirin and nonsteroidal antiinflammatory drugs have been shown to be effective in the chemoprevention of colorectal cancer by decreasing the risk of adenoma formation as well as the incidence and mortality of colorectal cancer.
Clinical Presentation
Numerous clinical features suggest the presence of rectal cancer, including:
• Located approximately 12 cm from the anal verge
• Rectal bleeding, often bright red and on the surface of the stool
• Subtle changes in bowel habits
• Decreased caliber of stool; mucus in stool
• Sensation of fullness and tenesmus
• Increased straining during defecation
• Synchronous colon cancer (in 2% to 9% of patients with rectal cancer)
Staging and Assessment
• Careful rectal examination yields 67% to 84% accuracy in staging (superficial, mobile, tethered, fixed) and should include pelvic examination for women and prostate examination in men.
• Rigid proctosigmoidoscopy provides the most accurate assessment of distance, size, and position, as well as tethering to surrounding structures.
• Colonoscopy, colonography, or double-contrast barium enema is used to assess for synchronous colon tumors.
• Endorectal ultrasound can assess the depth of invasion and nodal status. Nodal assessment is less reliable.
• Magnetic resonance imaging (MRI) with endorectal coil and ultrasound are useful to stage rectal cancer and are more sensitive and specific than computed tomography (CT) alone. MRI is used to assess locally advanced or recurrent local disease. CT should be performed on all patients to assess intraabdominal spread. CT or chest x-ray is required to evaluate for synchronous lung metastases.
• The liver is the most frequent site of distant spread, followed by lung, retroperitoneum, ovary, and peritoneal cavity.
• Baseline carcinoembryonic antigen (CEA) levels are assessed and followed postoperatively, even if initially normal.
Treatment
• Goals of treatment are cure, local control, and quality of life.
• All retrorectal tumors should be resected, and preoperative biopsy must be avoided.
• Full-thickness local excision is feasible for highly selected patients with T1 mucosal, submucosal, and early invasive cancer, particularly in patients with high-risk comorbidities.
• For T1 to T3 rectal adenocarcinomas, surgical procedures are total mesorectal excision, low anterior resection, low colorectal or coloanal anastomosis with J pouch, and abdominoperineal resection, leaving at least a 2-cm distal margin and clear lateral margins. With surgery, mortality rates are 1% to 7% and morbidity rates are 13% to 46%. The survival rate at 5 years is 74% to 87%.
• Combined therapy cures 50% of N1 patients; 25% of tethered or fixed rectal cancers treated by neoadjuvant chemoradiotherapy are subsequently resected and cured.
• Of patients who die of rectal cancer, 25% fail with pelvic disease only.
1. Imaging features, pros-cons of different strategies. A 68-year-old man presented to his family doctor with rectal bleeding. Physical exam, including a rectal exam were unremarkable. Colonoscopy revealed a mass in the rectum, 9 cm from the anal verge. The mass measured 5 cm and occupied two-thirds of the circumference of the bowel. Remainder of the colonoscopy to the cecum was unremarkable. Biopsy of the mass confirmed moderately differentiated adenocarcinoma. Blood tests revealed a Hgb of 10.8, normal liver function tests, and a carcinoembryonic antigen of 2.1. In planning his treatment, the best next step is:
