A cancer that begins in the colon is often called colon cancer and a cancer that begins in the rectum is often called rectal cancer, but sometimes the term colorectal cancer is used for a cancer that begins in either place. This year about 132,700 people in the U.S. will be diagnosed with cancer of the colon or rectum. However, nearly 1.1 million remain alive today after having been diagnosed with colorectal cancer.
The colon and rectum are parts of the large intestine. In the colon, which accounts for most of the length of the large intestine, water and nutrients are extracted from partly-digested food before the food is turned into waste. The waste then enters the rectum before being pushed out of the body, leaving via the short anal canal and the anus (cancers also develop in the anus and anal canal, but they aren't classified as colorectal cancers). Most colon cancers and rectal cancers are adenocarcinomas, tumors that begin in gland-like cells lining the colon or rectum. Other types of cancerous tissues account for only 2% to 5% of colorectal cancers.
Colorectal cancer (and other tumors) can spread (metastasize) from the place where it started (the primary tumor) in 3 ways. First, it can invade the normal tissue surrounding it. Second, cancer cells can enter the lymph system and travel through lymph vessels to distant parts of the body. Third, the cancer cells can get into the bloodstream and go to other places in the body. In these distant places, the colon/rectal cancer cells cause secondary tumors to grow. The main sites to which colorectal cancer spreads are the liver, lungs and peritoneum. To find out whether the cancer has entered the lymph system, a surgeon removes all or part of a node near the primary tumor and a pathologist examines it to see if cancer cells are present. Several kinds of imaging also can be performed to determine if the cancer has spread. These include chest x-rays, MRI, CT scans and PET scans.
The FDA has approved several targeted therapies for treatment of patients with metastatic colorectal cancer. These include bevacizumab (Avastin), cetuximab (Erbitux), panitumumab (Vectibix) and ziv-afibercept (Zaltrap).
Despite significant improvements in the treatment of colorectal cancers, novel therapies and treatment strategies are needed.
Source: National Cancer Institute, 2015
The prognosis of patients with colon cancer is clearly related to the degree of tumor penetration through the bowel wall, the presence or absence of nodal involvement, and the presence or absence of distant metastases. These three characteristics form the basis for all staging systems developed for this disease. Bowel obstruction and bowel perforation are indicators of poor prognosis. Elevated pretreatment serum levels of carcinoembryonic antigen (CEA) have a negative prognostic significance. The American Joint Committee on Cancer and a National Cancer Institute-sponsored panel recommended that at least 12 lymph nodes be examined in patients with colon and rectal cancer to confirm the absence of nodal involvement by tumor. This recommendation takes into consideration that the number of lymph nodes examined is a reflection of the aggressiveness of lymphovascular mesenteric dissection at the time of surgical resection and the pathologic identification of nodes in the specimen. Retrospective studies demonstrated that the number of lymph nodes examined in colon and rectal surgery may be associated with patient outcome.
Many other prognostic markers have been evaluated retrospectively for patients with colon cancer, though most have not been prospectively validated (including allelic loss of chromosome 18q or thymidylate synthase expression). Microsatellite instability, also associated with hereditary nonpolyposis colon cancer (HNPCC), has been associated with improved survival (independent of tumor stage) in a population-based series of 607 patients younger than 50 years of age with colorectal cancer. Treatment decisions generally depend on factors such as physician/patient preferences and the stage of the disease, rather than the age of the patient. Racial differences in overall survival after adjuvant therapy have been observed (although not in disease-free survival), suggesting that comorbid conditions play a role in survival outcome in different patient populations.
Source: National Cancer Institute, 2012
Cancer research and treatments are constantly changing. Knowing the gene associated with your cancer can help doctors determine the most appropriate direction of care for you. To learn how you can find out more about genetic testing please visit http://www.massgeneral.org/cancer/news/faq.aspx
or contact the Cancer Center.
The mutation of a gene provides clinicians with a very detailed look at your cancer. Knowing this information could change the course of your care. To learn how you can find out more about genetic testing please visit http://www.massgeneral.org/cancer/news/faq.aspx
or contact the Cancer Center.