The colon and rectum can be found between the small intestines and the anus in the digestive system. The colon consists of 4 sections (from nearest to and furthest from the small intestines): ascending colon, transverse colon, descending colon and sigmoid colon.
Colorectal cancer starts in the colon or the rectum and have many features in common. Colorectal cancer generally develops slowly from a non-cancerous polyp on the inner lining of the colon/rectum. Of the different types of polyps, most cancers arise from adenomatous polyps (adenomas). Other colorectal polyps such as hyperplastic polyps and inflammatory polyps, in general, are not pre-cancerous but may be a sign of greater risk to develop adenomas and colorectal cancer.
More than 95% of colorectal cancers are adenocarcinomas, which arise from adenomas. There are other less common colorectal tumors but the focus for this document is on adenocarcinoma of the colon and rectum.
A change in bowel habits that lasts for more than a few days; diarrhea or constipation; narrowing of the stool; feeling that the bowel does not empty completely; rectal bleeding, dark stools, or blood in the stool; cramping or abdominal pain or discomfort; weakness and fatigue; unintended weight loss; unexplained iron-deficiency anemia.
For average-risk individuals, routine colonoscopies every 10 years, or flexible sigmoidoscopies every 5 years starting at age 50, is recommended unless otherwise indicated by findings. Alternatives include annual FOBT or FIT stool testing with or without flexible sigmoidoscopy every 5-10 years, CT-colonography every 5 years, double-contrast barium enema every 5 years, or flexible sigmoidoscopy alone. Screening for those at increased risk, including those with a history of polyps, may involve more frequent colonoscopy screening beginning at an age earlier than 50.
|Early stage cancer||
Surgery is typically used to remove the part of the colon with cancer and nearby lymph nodes. If the cancer is found at a very early stage, a local excision, where the cancer is removed without cutting through the abdominal wall, may be performed. Otherwise, resection (removing a section of the affected colon) and anastomosis (connecting the resected ends) may be considered.
|Advanced stage cancer||
How much colon is removed differs between individuals and is based on the aggressiveness and location of the cancer and how high risk the patient is for second primary tumors.
Surgery removing a part or the entire colon (resection and anastomosis) as well as surrounding tissues, affected organs, and lymph nodes may be performed, followed by adjuvant chemotherapy.
The surgical approach to rectal cancer differs from that of colon cancer, because issues related to maintaining or restoring normal anal sphincter, genitourinary, and sexual functions need to be considered.
Radiation therapy is often used in combination with chemotherapy to treat rectal cancer.
|Metastatic stage cancer||
After surgical resection on affected organs, if feasible, chemotherapy, targeted therapy and/or radiation therapy may be used to treat metastases. Palliative surgeries may be performed for unresectable cancers to control growth or to prevent or relieve symptoms/ complications.
Demographics: Older age, ethnicity - African, Ashkenazi Jewish
Lifestyle: Diet high in red meats and processed meats; tobacco use; low intake of fruits & vegetables; obesity; physical inactivity; heavy alcohol use
Medical History: History of adenomatous polyps or colorectal cancer diagnosis; chronic inflammatory bowel disease; type 2 diabetes; radiation exposure
Risk reduction options: Healthy diet; physical activity; long-term regular nonsteroidal anti-inflammatory drugs (NSAIDS) use; routine screening and removal of polyps
Inherited: Family history of polyps or colorectal cancer diagnosis; inherited genetic syndromes
Associate Genes: MLH1, MSH2, MSH6, PMS2, EPCAM, APC, MUTYH Monoallelic, MUTYH Biallelic, TP53, PTEN, STK11, CDH1, BMPR1A, SMAD4, CHEK2, CHEK2 Biallelic, POLD1, POLE, GREM1, AXIN2, GALNT12, RPS20, RNF43
Associated Myriad MyRisk™ Genes: MLH1, MSH2, MSH6, PMS2, EPCAM, APC, MUTYH, TP53, PTEN, STK11, CDH1, BMPR1A, SMAD4, CHEK2