Cancer that affects the colon, which is part of the large intestine or large bowel, is termed as colon cancer, while cancer in the rectum, which is the passageway that connects the colon to the anus, is termed rectal cancer. Often they are classified as a single term, colorectal cancer.
Colorectal cancer is the third most commonly diagnosed cancer in both men and women. Reliable statistics on colon and rectal cancers separately are not available since almost 40% of deaths from rectal cancer are misclassified as colon cancer on death certificates.
The current incidence rates for colon cancer appear to be in decline in persons aged 50 and older, in western countries, a trend thought to be largely a result of screening programs which are compulsory in many countries. Most colon cancers develop first as polyps, which are abnormal growths inside the colon or rectum that may later become cancerous if not removed. Screening can identify and remove precancerous polyps in the colon, and prevent colon cancer.
However, contrasting results have been recently found. Younger adults are increasingly being diagnosed with colon cancer, at ages when they should be nearing the age to begin screening programs. Cancer, among this subset of population, is especially alarming as, most often, the cancer is at an advanced stage.
Obesity, a diet high in red or processed meats and lack of physical activity are among the factors tied to increased risk, but new research is looking at other possible causes. A recent study indicated that prolonged use of antibiotics during adulthood was associated with a greater risk of developing precancerous polyps, possibly because antibiotics can alter the makeup of the gut microbiome.
Symptoms include a change in bowel habits, including diarrhea or constipation or a change in the consistency of stool, that lasts longer than four weeks, rectal bleeding or blood in the stool, persistent abdominal discomfort, such as cramps, gas or pain, feeling that the bowel doesn’t empty completely, weakness or fatigue, unexplained weight loss. The stage is one of the most important factors in deciding how successful treatment might be and is based on the TNM classification. Early stages include 0, 1, and II (a, b, and c) where the tumor has not infiltrated to the nearby structures. The cancer may be advanced in stages III and IV depending on extent of spread as determined by imaging and pathology reports.
Colon cancer, when discovered early, is highly treatable. Even if it spreads into nearby lymph nodes, surgical treatment followed by chemotherapy is highly effective. In the most difficult cases — when the cancer has spread to the liver, lungs or other sites — treatment can help make surgery an option for many, as well as prolonging and adding to one’s quality of life.
Most patients with colon cancer are adequately treated with surgery with or without adjuvant systemic therapy. There is an established role for the routine use of radiation as an adjuvant (additionally enhancing) therapy in colon cancer. Radiation plays an important role in patients with locally advanced disease that is not amenable to surgery or in patients with local recurrence in organs and tissues located behind the peritoneum. Current recommendations include patients with T3 &T4 cancer stage.
Recurrent disease patients that may benefit include tumor bed recurrences as well as locally advanced nodal recurrences. Intraoperative radiotherapy has also been found as a useful tool as evidenced by improved survival rates .Stereotactic Body Radiotherapy (SBRT) is proving an additional way of tackling liver and lung metastases from Colon cancer.