Rectum

Eyob, Bret , Dustin , Faleesa , Jake , Holly , Nick
 * **Epidemiolgy:** || In the United States each year about 42,000 individuals are diagnosed with rectal cancer, and 8,500 die of this disease. 1 As with colon cancer, Western nations tend to have a higher incidence than Asian and African countries and incidence peaks in the sixth and seventh decades. In spite of the low incidence of cancer in Africa, survival rates are very low, not exceeding 55% at 5 years in Zimbabwe. This has been explained by poor distribution of resources among other reasons. These figures are expected to worsen in the future due to increased urbanization, adoption of the Western diet and relatively poor funding for cancer-related conditions in Africa. ||
 * **Etiology:** || Etiology is multifactorial in origin. It includes environmental factors, such as diet, and a large genetic component. 1 In the West about two thirds of cases are sporadic and develop in people with no specific risk factors; while the other one-third occur in people with either a positive family history or a personal history of colorectal cancer or polyps. A smaller percentage occur in people with genetic predispositions, such as hereditary nonpolyposis colorectal cancer or familial adenomatous polyposis. ||
 * **Signs & Symptoms:** || The most common signs and symptoms of rectal cancer patients include 2 :
 * Rectal Bleeding (Most common)
 * Change in bowel habits
 * Diarrhea versus constipation
 * Change in stool caliber
 * Pencil-thin stools
 * Tenesmus
 * Pain
 * Nausea
 * Vomiting ||
 * **Diagnostic Procedures:** || Diagnostic procedures for rectal cancers include 2 :
 * Physical Exam
 * Digital Rectal Exam
 * Endoscopy
 * Pelvc Examination (women)
 * CT
 * MRI
 * Laboratory Studies
 * PET ||
 * **Histology:** || Adenocarcinomas account for the vast majority of rectal cancers. 3 Other histologic types of colorectal cancer account for an estimated 2% to 5% of colorectal tumors. The World Health Organization (WHO) classification of tumors of the colon and rectum include the following:
 * Epithelial Tumors
 * Adenoma
 * Tubular
 * Villous
 * Tubulovillous
 * Serrated
 * Intraepithelial neoplasia (dysplasia) associated with chronic inflammatory diseases
 * Low-grade glandular intraepithelial neoplasia
 * High-grade glandular intraepithelial neoplasia
 * Carcinoma
 * Adenocarcinoma
 * Mucinous adenocarcinoma
 * Signet-ring cell carcinoma
 * Small cell carcinoma
 * Adenosquamous carcinoma
 * Medullary carcinoma
 * Undifferentiated carcinoma
 * Carcinoid (well-differentiated neuroendocrine neoplasm)
 * Mixed carcinoma-adenocarcinoma

G1 Well differentiated G2 Moderately differentiated G3 Poorly differentiated G4 Undifferentiated || Initial posteroanterior (A) and lateral (B) irradiation fields used in adjuvant treatment of rectal cancer. In patients with tumor adherence to prostate, bladder, vagina, or uterus, the anterior border of lateral field is modified so that it is anterior to the symphysis pubis to provide coverage of the external iliac nodes. (APR, abdominoperineal resection; AR, anterior resection.) (From Martenson JA Jr, Schild SE, Haddock MG. Cancers of the gastrointestinal tract. In: Khan FM, Potish RA, eds. //Treatment Planning in Radiation Oncology//. Baltimore, MD: Williams & Wilkins, 1997.) || Bladder: 65 Gray (Gy): Bladder contracture and volume loss Femoral head: 52Gy: Necrosis Spinal cord: 20cm 47Gy: Myelitis necrosis Colon: 45Gy: Obstruction, perforation, ulceration, fistula ||
 * Nonepithelial Tumors
 * Lipoma
 * Leiomyoma
 * Gastrointestinal stromal tumor
 * Leiomyosarcoma
 * Angiosarcoma
 * Kaposi sarcoma
 * Melanoma
 * Others
 * Malignant lymphomas ||
 * **Lymph node drainage:** || Lymphatic drainage of the upper rectum is through the superior rectal vessels into the inferior mesenteric system. The middle and lower rectum lymphatic drainage is through the middle rectal vessels, with the main nodal group being the internal iliac nodes. 2 ||
 * **Metastatic spread:** || Rectal CA metastasize by direct extension, lymphatic’s, and homatogenous spread. 2 The initial lymphatic spread is through the perirectal nodes. Metastasis by blood is most common to the liver because venous drainage of the gastrointestinal system. The lung is the second most common site for mets due to embolus into the inferior vena cava. ||
 * **Grading:** || GX Grade cannot be assessed 2
 * **Staging:** || The American Joint Committee on Cancer uses the tumor-node-metastasis system (TNM) system for staging of rectal cancer. One advantage of this system is it can be used clinically for preoperative and postoperative cases. 4 T is used to describe how far the primary tumor has grown into the wall of the bowel of if the tumor has grown into surrounding tissue. N describes any lymph node involvement and M indicates any spread or metastasis to other parts of the body. Each letter in the TNM system can be followed by a number between 0 and 4, which can indicate the severity. If the letter X is ever used then the information was not given or available to be assessed. ||
 * **Radiation side effects:** || Side effects from radiation therapy are directly related to dose, volume, and tissue irradiated. Acute toxicities of treatment include diarrhea, abdominal cramps, bloating, proctitis, bloody or mucus discharge, and dysuria. 2 If the patient is having the perineum treated, then a severe skin reaction may require the need for a break. Chronic effects occur less often than acute side effects but can be more serious. Diarrhea, increased frequency, proctitis, urinary incontinence, and bladder atrophy can occur. The most common long-term complication is damage to the small bowel, resulting in enteritis, adhesions, and obstruction. 2 ||
 * **Prognosis:** || * Tumor penetration of the bowel wall and lymph node involvement, both are associated with increased risk of local recurrence. 4
 * # and proportion of involved lymph nodes
 * Presence of extension into bowel wall and lymph node involvement is more ominous than the presence of either alone.
 * 5-year survival is 62% with chemo alone, and 58% with chemoradiation therapy
 * 5-year disease-free survival is 51% ||
 * **Treatments:** || * Shrinking field technique should be used - initial fields include the primary tumor in addition to lymph nodes 4
 * Smaller fields used to treat the primary tumor bed to higher volumes
 * Width of PA field should cover entire pelvic inlet with a 2 cm margin; the superior margin is 1.5 cm above the level of the sacral promontory
 * If patient had anterior resection, usual inferior margin is below the obturator foramen
 * Lateral fields used as a portion help spare the small bowel
 * Prone positions also help displace the small bowel
 * Lateral fields- posterior margin should be at least 1.5 to 2.0 cm behind the anterior bony sacral margin
 * Entire sacral canal should be included for locally advanced disease
 * Radiopaque markers can be used to outline perineal scar during simulation
 * Mobile lesions- 20-25 Gy in 4-5 Fx pre-op; more advanced- 45 Gy in 25 Fx
 * In patients with distal lesions, the posterior vaginal wall or prostate should be included
 * Dose to large fields, including tumor bed and regional lymph nodes, should be 45 Gy in 5 weeks. Then boost to 50.4 Gy with small bowel out of field.
 * **Endocavitary radiation** can be performed, introducing a 3 cm diameter applicator into the rectum after verification by ultrasound
 * Four 30-Gy treatments separated by 2 weeks
 * **TD 5/5:** || Tolerance doses that within 5 years will cause a minimum 5% complication rate. 4
 * **References:** || # Rectal cancer. Ptolemy project Web site. http://www.ptolemy.ca/members/archives/2008/Rectalca/#T3. Accessed June 11, 2013.
 * 1) Washington CM, Leaver D. // Principles and Practice of Radiation Therapy // . 3rd ed. St. Louis, MO: Mosby Elsevier; 2010.
 * 2) Cellular Classification and Pathology of Rectal Cancer. National Cancer Institute Web site. [] . Assessed June 10, 2013.
 * 3) Chao K, Perez C, Brady L. //  Radiation Oncology Management Decisions.  // 3rd ed. Philadelphia, PA: Lippincott, Williams & Wilkins; 2011. ||

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