Colon


 * **Epidemiolgy:** || Risk of development increases with age, but no gender difference has been demonstrated.[1] ||
 * **Etiology:** || Dietary factors, especially diets high in animal fats and meat and low in fiber and calcium, chronic ulcerative colitis, familial adenomatous polyposis. An increased risk is demonstrated in patients with a first degree family member diagnosed with colorectal cancer before the age of 60.[1,2] ||
 * **Signs & Symptoms:** || Most common sign of lower sigmoid colon and rectal cancer is hematochezia (blood in stool). Abdominal pain is a common complaint with colon cancer. Other indicators include change in bowel habits, nausea and vomiting, abdominal mass and anemia.[2] ||
 * **Diagnostic Procedures:** || The diagnosis of colon cancer involvesan extensive work up of including a history and physical examination, laboratory, colonoscopy and medical imaging studies. A colonoscopy is often done to examine the extent of the tumor and to obtain biopsies of the tumor. If a colonoscopy is not possible, barium enema x-rays can be obtained. Abdominal pelvis computed tomography or magnetic resonance imaging studies are also used. The carcinoembryonic antigen is often used as a prognostic tool as a molecular marker. [2] ||
 * **Histology:** || The most common histologic type of colon cancer is adenocarcinoma. It accounts for more than ninety percent of all colon cancer. It is further classified by cellular differentiation. Colloid or mucinous adenocarcinoma accounts for 17 percent of colon tumors.These tumors are defined by the amount of extracellular mucin retained within the tumor. Also, a rare type of tumor of the colon, known as signet-ring cell carcinoma//,// is known to have a poor prognosis. [2,3] ||
 * **Lymph node drainage:** || The lymphatic drainages of the colon are through the lymphatic channels along the major arteries. The lymphatics of the left colon follow the inferior mesenteric vessels and the lymphatics of the right colon follow the superior mesenteric vessels. The iliac lymph nodes can also be involved if the tumor is located in the true and false pelvis. Also, tumors invading the retroperitoenum, periaortic and external iliac nodes can be involved. [3] ||
 * **Metastatic spread:** || May spread to iliac nodes or periaortic lymph nodes. ||
 * **Grading:** || Tumor Grading for Large Bowel Cancer.

G1: Well differentiated (low grade). G2: Moderately differentiated (intermediate grade). G3: Undifferentiated (high grade). || Tis No extension through muscularis mucosa T1 Invades submucosa T2 Invades muscularis propria T3 Invades through the muscularis propria into perirectal fat T4 Perforates the visceral peritoneum or invades other organs or structures N0 No involved nodes N1 1-3 involved nodes N2 >4 involved nodes M0 No distant metastatic disease M1 Distant metastatic disease
 * **Staging:** || __TNM Staging System for Large Bowel Cancer__ [2]

Stage Groupings I = T1-2, N0, M0 II = T3-4, N0, M0  III = any T, N1-2, M0  IV = any T, N, M1 || Absolute number and proportion of lymph nodes involved are also important predictors of outcome. Presence of both lymph node involvement and extension of disease beyond the bowel wall is more ominous than the presence of either alone. The higher the stage, the worse the prognosis.[3]
 * **Radiation side effects:** || Constipation is the most common acute toxicity during pelvic irradiation. Patients may experience consistently worse bowel function when receiving irradiation and chemotherapy. Ulcers may also develop in patients with intracavitary radiation therapy.[2] ||
 * **Prognosis:** || Tumor penetration of the bowel wall and lymph node involvement are important prognostic factors.They are associated with the increased risk of local recurrence.

Stage 5-year Survival Rate I 74% IIA 67% IIB 59% IIC 37% IIIA 73% IIIB 46% IIIC 28% IV 6% || Radiation treatment after surgery does not help people with colon cancer, but it does prolong survival for people with rectal cancer. Given before surgery, radiation may reduce tumor size. This can improve the chances that the tumor will be removed successfully. Radiation before surgery also appears to reduce the risk of the cancer coming back after treatment. [2] || Bladder 80 Gy 65 Gy Rectum 60 Gy  Femoral Head 52Gy Spinal cord 47 Gy(20 cm) 50 Gy(10 cm) 50(5 cm) [2] || [2] Chao KS, Perez CA, Brady LW. //Radiation Oncology Management Decisions//. 2nd ed. Lippincott Williams & Wilkins; 2002. [3] Hoppe TR, Phillips LT, Roach M. Leibel and Phillips Textbook of Radiation Oncology. 3rd Edition. Philadelphia: Saunders, Elsevier. 2010 || Back to Week 3
 * **Treatments:** || The primary treatment of colon cancer is to surgically remove part or the entire colon. Suggestive polyps, if few in number, may be removed during colonoscopy. Chemotherapy after surgery can prolong survival for people whose cancer has spread to nearby lymph nodes.
 * **TD 5/5:** || __ ORGAN WHOLE ⅓ __
 * **References:** || [1] Washington CM, Leaver D. //Principles and Practice of Radiation Therapy//. 2nd ed. Mosby; 2004.