Colorectal cancer happens when cells that are not normal grow in your colon or rectum . These cells grow together and form polyps. Over time, some polyps can turn into cancer. This cancer is also called colon cancer or rectal cancer, depending on where the cancer is.
Metastatic cancer is cancer that has spread to other parts of the body. When colon or rectal cancer spreads, it most often spreads to the liver. Sometimes it spreads to the lungs, bones, or other organs in the body.
Colorectal cancer (CRC) is the third most commonly diagnosed malignancy and the fourth leading cause of cancer-related deaths in the world, and its burden is expected to increase by 60% to more than 2.2 million new cases and 1.1 million cancer deaths by 2030.
Colorectal cancer (CRC) incidence and mortality rates vary markedly around the world. Globally, CRC is the third most commonly diagnosed cancer in males and the second in females, with 1.4 million new cases and almost 694,000 deathsestimated to have occurred in 2012 . Rates are substantially higher in males than in females. Global, country specific incidence and mortality rates are available in the World Health Organization GLOBOCAN database.
In the United States, both the incidence and mortality have been slowly but steadily decreasing . Annually, approximately 135,430 new cases of large bowel cancer are diagnosed, of which 95,520 are colon and the remainder are rectal cancers . Annually, approximately 50,260 Americans die of CRC, accounting for approximately 8 percent of all cancer deaths.
Incidence — Globally, the incidence of CRC varies over 10 fold. In the latest data from 2012 from the Globocandatabase, the highest incidence rates are in Australia and New Zealand, Europe, and North America, and the lowest rates are found in Africa and SouthCentral Asia. These geographic differences appear to be attributable to differences in dietary and environmental exposures that are imposed upon a background of genetically determined susceptibility.
Low socioeconomic status (SES) is also associated with an increased risk for the development of CRC; one study estimated the CRC risk to be about 30 percent increased in the lowest as compared with the highest SES quintile . Potentially modifiable behaviors such as physical inactivity, unhealthy diet, smoking, and obesity are thought to account for a substantial proportion (estimates of onethird
toonehalf) of the socioeconomic disparity in risk of new onset CRC .
Other factors, particularly lower rates of CRC screening, also contribute substantively to SES
differences in CRC risk.
Colorectal cancer Symptoms
Early CRC often has no symptoms, which is why screening is so important. As a tumor grows, it may bleed or obstruct the intestine. In some cases, blood loss from the cancer leads to anemia (low number of red blood cells), causing symptoms such as weakness, excessive fatigue, and sometimes shortness of breath. Additional warning signs include:
- Bleeding from the rectum
- Blood in the stool or in the toilet after having a bowel movement
- Dark or black stools
- A change in bowel habits or the shape of the stool (e.g., more narrow than usual)
- Cramping or discomfort in the lower abdomen
- An urge to have a bowel movement when the bowel is empty
- Constipation or diarrhea that lasts for more than a few days
- Decreased appetite
- Unintentional weight loss
How Colorectal cancer Spread/Transmitted
Colorectal cancer usually begins as a noncancerous growth called a polyp that develops on the inner lining of the colon or rectum and grows slowly, over a period of 10 to 20 years.4, 5 An adenomatous polyp, or adenoma, is the most common type. Adenomas arise from glandular cells, which produce mucus to lubricate the colorectum. About one-third to one-half of all individuals will eventually develop one or more adenomas.6, 7 Although all adenomas have the potential to become cancerous, fewer than 10% areestimated to progress to invasive cancer.8, 9 The likelihood that an adenoma will become cancerous increases as it becomes larger.10 Cancer arising from the inner lining of the colorectum is called adenocarcinoma and accounts for approximately 96% of all CRCs.
Once cancer forms in the inner lining of the large intestine, it can grow into the wall of the colon or rectum . Cancer that has grown into the wall can also penetrate blood or lymph vessels, which are thin channels that carry away cellular waste and fluid. Cancer cells typically spread first into nearby lymph nodes, which are bean-shaped structures that help fight infections. Cancer cells can also be carried in blood vessels to other organs and tissues, such as the liver, lungs, or peritoneum (membrane lining the abdomen). The spread of cancer cells to parts of the body distant from where the tumor originated is called metastasis.
Regional: Cancers that have spread through the wall of the colon or rectum and have invaded nearby tissue, or that have spread to nearby lymph nodes
Distant: Cancers that have spread to other parts of the body, such as the liver or lung
Prevention of Colorectal cancer
There is no sure way to prevent colorectal cancer. But there are things you can do that might help lower your risk, such as changing the risk factors that you can control.
Colorectal cancer screening
Screening is the process of looking for cancer or pre-cancer in people who have no symptoms of the disease. Regular colorectal cancer screening is one of the most powerful weapons for preventing colorectal cancer.
From the time the first abnormal cells start to grow into polyps, it usually takes about 10 to 15 years for them to develop into colorectal cancer. With regular screening, most polyps can be found and removed before they have the chance to turn into cancer. Screening can also find colorectal cancer early, when it is highly curable.
Screening is recommended starting at age 50 for people who are not at increased risk of colorectal cancer. There are several different screening options available. People at higher risk, such as those with a strong family history of colorectal cancer, might benefit from starting screening at a younger age.
If you have a strong family history of colorectal polyps or cancer, talk with your doctor about your risk. You might benefit from genetic counseling to review your family medical tree to see how likely it is that you have a family cancer syndrome.
Body weight, Physical activity, and Diet
You might be able to lower your risk of colorectal cancer by managing some of the risk factors that you can control, like diet and physical activity.
Weight: Being overweight or obese increases the risk of colorectal cancer in both men and women, but the link seems to be stronger in men. Having more belly fat (that is, a larger waistline) has also been linked to colorectal cancer. Staying at a healthy weight and avoiding weight gain around the midsection may help lower your risk.
Physical activity: Increasing your level of activity lowers your risk of colorectal cancer and polyps. Regular moderate activity (doing things that make you breathe as hard as you would during a brisk walk) lowers the risk, but vigorous activity might have an even greater benefit. Increasing the intensity and amount of your physical activity may help reduce your risk.
Diet: Overall, diets that are high in vegetables, fruits, and whole grains (and low in red and processed meats) have been linked with lower colorectal cancer risk, although it’s not exactly clear which factors are important. Many studies have found a link between red meats (beef, pork, and lamb) or processed meats (such as hot dogs, sausage, and lunch meats) and increased colorectal cancer risk.Limiting red and processed meats and eating more vegetables and fruits may help lower your risk.
In recent years, some large studies have suggested that fiber in the diet, especially from whole grains, may lower colorectal cancer risk. Research in this area is still under way.
Alcohol: Several studies have found a higher risk of colorectal cancer with increased alcohol intake, especially among men.Avoiding excess alcohol may help reduce your risk.
Long-term smoking is linked to an increased risk of colorectal cancer, as well as many other cancers and health problems. Quitting smoking may help lower you risk of colorectal cancer and other types of cancer.
Vitamins, calcium, and magnesium
Some studies suggest that taking a daily multi-vitamin containing folic acid, or folate, may lower colorectal cancer risk, but not all studies have found this. In fact, some studies have hinted that folic acid might help existing tumors grow. More research is needed in this area.
Some studies have suggested that vitamin D, which you can get from sun exposure, in certain foods, or in a vitamin pill, might lower colorectal cancer risk. Because of concerns that excess sun exposure can cause skin cancer, most experts do not recommend this as a way to lower colorectal cancer risk at this time.More studies are needed to determine if vitamin D can help prevent colorectal cancer.
Low levels of dietary calcium have been linked with an increased risk of colorectal cancer in some studies. Other studies suggest that increasing calcium intake may lower colorectal cancer risk. Calcium is important for a number of health reasons aside from possible effects on cancer risk. But because of the possible increased risk of prostate cancer in men with high calcium intake, the American Cancer Society does not recommend increasing calcium intake specifically to try to lower colorectal cancer risk.
Calcium and vitamin D might work together to reduce colorectal cancer risk, as vitamin D aids in the body’s absorption of calcium. Still, not all studies have found that supplements of these nutrients reduce risk.
A few studies have found a possible link between a diet that is high in magnesium and reduced colorectal cancer risk, especially among women. More research is needed to determine if this link exists.
Non-steroidal anti-inflammatory drugs (NSAIDs)
Many studies have found that people who regularly take aspirin or other non-steroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen (Motrin, Advil) and naproxen (Aleve), have a lower risk of colorectal cancer and polyps.
But aspirin and other NSAIDs can cause serious or even life-threatening side effects such as bleeding from stomach irritation or stomach ulcers, which may outweigh the benefits of these medicines for the general public. For this reason, most experts don’t recommend taking NSAIDs just to lower colorectal cancer risk if you are someone at average risk.
However, for some people in their 50s who have an elevated risk of heart disease, where low-dose aspirin is found to be beneficial, the aspirin may also have the added benefit of reducing the risk of colorectal cancer.
Because aspirin or other NSAIDs can have serious side effects, check with your doctor before starting any of them on a regular basis.
Hormone replacement therapy for women
Taking estrogen and progesterone after menopause (sometimes called menopausal hormone therapy or combined hormone replacement therapy) may reduce a woman’s risk of developing colorectal cancer, but cancers found in women taking these hormones after menopause may be at a more advanced stage.
Because taking estrogen and progesterone after menopause can also increase a woman’s risk of heart disease, blood clots, and cancers of the breast and lung, it is not commonly recommended just to lower colorectal cancer risk.
Treatment for CRC has advanced rapidly over the past several decades, including improvements in imaging, surgical techniques, and chemotherapy.However, it has also become increasingly clear that treatment outcomes vary widely based on tumor-specific molecular features.Treatment decisions are made by patients with their physicians after considering the best options available for the stage, location, and other tumor characteristics, as well as the risks and benefits associated with each.
Most people with colon cancer will have some type of surgery to remove the tumor. Adjuvant chemotherapy (chemotherapy given after surgery) may also be used. Radiation is used less often to treat colon cancer.
Carcinoma in situ
Carcinoma in situ is cancer that has not spread beyond the layer of cells in which it began. Surgery to remove the growth of abnormal cells may be accomplished by polypectomy (polyp removal) or local excision through the colonoscope. Resection of a segment of the colon may be necessary if the tumor is too large to be removed by local excision or if cancer cells are found after the polyp is removed.
Localized stage refers to invasive cancer that has penetrated the wall of the colon. Surgical resection to remove the cancer, together with a length of colon on either side of the tumor and nearby lymph nodes, is the standard treatment.
Regional stage includes cancers that have grown through the wall of the colon, as well as cancers that have spread to nearby lymph nodes. If the cancer has only grown through the wall of the colon but has not spread to nearby lymph nodes, surgical resection of the segment of colon containing the tumor and the surrounding lymph nodes may be the only treatment needed. If the cancer is likely to come back because it has spread to other tissues or has high-risk characteristics, chemotherapy may also be recommended. If the cancer has spread to nearby lymph nodes, surgical resection of the segment of colon containing the tumor is the first treatment, usually followed by chemotherapy. Adjuvant chemotherapy based on the drug fluorouracil (5-FU) is typically used in patients with stage III or high-risk stage II disease who are in otherwise good health.Oxaliplatin is often part of adjuvant chemotherapy as well.However, some patients may not tolerate this regimen given its toxicity, and there is growing appreciation for the need to confine its use to those patients who are most likely to benefit.Adjuvant chemotherapy for colon cancer is as effective in patients ages 70 and older (almost half of all patients) who are otherwise as healthy as younger patients, although certain drugs (e.g., oxaliplatin) may be avoided to limit toxicity. However, studies indicate that individuals 75 and older are far less likely than younger patients to receive this treatment.
At this stage, the cancer has spread to distant organs and tissues, such as the liver, lungs, peritoneum (lining of the abdomen), or ovaries. When surgery is performed, the goal is usually to relieve or prevent blockage of the colon and to prevent other local complications. If there are only a few metastases to the liver or lungs, surgery to remove these, as well as the colon tumor, may improve survival.
Chemotherapy and biologically targeted therapies may be given alone or in combination to relieve symptoms and prolong survival. A number of targeted therapies have been approved in recent years by the US Food and Drug Administration to treat metastatic CRC. Some of these drugs inhibit new blood vessel growth to the tumor by targeting a protein called vascular endothelial growth factor (VEGF). Others interfere with cancer cell growth by targeting the epidermal growth factor receptor (EGFR) or other proteins. Tumors with certain genetic mutations do not benefit from treatment with some of these drugs.