Colorectal cancer, or bowel cancer, is the collective term for colon and rectal cancers.1
Colorectal cancer is a form of cancer that develops when cells in the colon or rectum start to grow uncontrollably. The colon, also referred to as the large intestine or large bowel, is a component of the digestive system that absorbs water and nutrients from food. The rectum, on the other hand, links the colon to the anus and is in charge of storing and eliminating waste from the body.
Polyps are growths in the colon or rectum that may turn into cancer if left untreated. Screening tests can detect and help remove polyps before they become cancerous. Regular screening is also helpful in detecting colorectal cancer early when treatment has the best chance of success2.
Risk Factors
Cancer is caused by changes in genes, which can happen randomly or due to exposure to cancer-causing substances. The disease can be caused by environmental factors, viruses, or genetics.
The risk factors associated with cancer can be broadly categorized into different groups 3:
Biological or internal factors refer to age, gender, inherited genetic defects, and skin type,
environmental exposure includes exposure to radon and UV radiation, as well as to fine particulate matter,
occupational risk factors may include exposure to carcinogens such as many chemicals, radioactive materials, and asbestos, and
lifestyle-related factors can also contribute to the development of cancer.
Specific risk factors related to colorectal cancer 4:
Risk factors that can be changed include being overweight or obese, lack of physical activity, unhealthy diets, smoking, and alcohol use.
Risk factors for colorectal cancer that can’t be changed include personal history of polyps or colorectal cancer, inflammatory bowel disease, family history of colorectal cancer, and inherited syndromes, such as Lynch syndrome. Other risk factors include racial/ethnic background and type 2 diabetes.
Prevalence
Excluding skin cancers, colorectal cancer is the third most common cancer diagnosed in both men and women in the United States. The American Cancer Society estimates that there will be approximately 106,590 new cases of colon cancer and 46,220 new cases of rectal cancer in the United States in 2024.5
An estimated 3,500 people are diagnosed with bowel cancer annually in Finland, making it the country’s third most common cancer.1
Colon and rectal cancer diagnoses have decreased since the mid-1980s. Incidence rates fell by about 1% yearly from 2011 to 2019 due to screening and lifestyle changes. However, younger adults have seen an increase in rates by 1% to 2% annually since the mid-1990s.
The lifetime risk of developing colorectal cancer is approximately 1 in 23 for men and 1 in 26 for women. However, it’s essential to note that individual risk factors can affect one’s chances of developing colorectal cancer, which may make their risk higher or lower than the average.5
Background for inherited colorectal cancer caused by Lynch syndrome
Cancer isn’t inherited, but the risk of developing it can be. Identifying a genetic defect causing inherited cancer susceptibility directs carriers to more detailed monitoring and may affect treatment. Approximately 5% of all colorectal cancers are caused by a genetic predisposition that increases the risk of developing the disease.
Lynch syndrome is a hereditary cancer syndrome that increases the risk of colorectal and endometrial cancer. It is the most common type of hereditary colorectal cancer. Lynch syndrome is suspected when a person is diagnosed with colorectal or endometrial cancer at a young age, if multiple tumors are found in the same person, or if multiple close relatives have been affected by these cancers at a younger age than usual.6
A genetic predisposition to cancer can be identified by the occurrence of cancer at a young age or in multiple closely related family members with the same type of cancer. Hereditary factors are responsible for about 2-3% of new cases of colorectal cancer detected annually. For instance, in Finland, there are roughly 380 extended families in which a gene defect, leading to susceptibility to hereditary non-polyposis colorectal cancer (Lynch Syndrome), has been identified.7
Globally, Lynch syndrome is the most common hereditary cancer syndrome, affecting an estimated 30 million people worldwide, with a prevalence of 1 in 279.8
Symptoms
Colorectal cancer is almost asymptomatic in its early stages. Typical symptoms are changes in bowel function, new or varying diarrhea or constipation, a feeling that the bowel is not emptying properly, or bowel obstruction.9
The tumor’s surface has a rough texture, which causes it to bleed easily. As a result, the stool may contain clear blood or become dark. If the bleeding persists over an extended period, the patient may develop anemia, which causes symptoms such as shortness of breath, paleness, and dizziness.
Occasionally, people may experience general symptoms like weight loss, abdominal pain, and loss of appetite. Symptoms caused by metastases can vary depending on the organ affected. The liver, lungs, and distant lymph nodes are the most common sites of metastases. In such cases, patients may experience mild symptoms or be asymptomatic.9
Prognosis
Colorectal cancer is the second most common cause of cancer-related deaths in the Western world although a worldwide population-based study has shown that 5-year relative survival for colorectal cancer seems to be generally higher in high-income countries.10
In the United States, colorectal cancer is the third leading cause of cancer-related deaths in both men and women, and it’s the second most common cause of cancer deaths when numbers for men and women are combined. It’s expected to cause about 52,550 deaths during 2023.
The death rate from colorectal cancer has been decreasing in both men and women for several decades. There are numerous reasons for this positive trend. One of them is that colorectal polyps are now being detected more frequently through screening, and removed before they can develop into cancer. Screening also results in many colorectal cancers being discovered early on when they are more likely to be treatable. Moreover, advances in treatments for colorectal cancer have been made in recent decades.5
The outlook for individuals diagnosed with colon cancer largely depends on how far the cancer has spread. For those with early-stage tumors, the chances of recovery are generally positive, and many individuals can be cured through surgery alone or with the help of radiotherapy and/or chemotherapy. However, for those with more advanced cancer, the prognosis is typically less favorable.9
Prevention
A healthy lifestyle can prevent cancer by exercising regularly, eating a varied diet with lots of plant-based foods and fiber, and avoiding smoking, excessive drinking, and overexposure to the sun. Regular medical check-ups and participating in cancer screenings can also help in taking better care of oneself.
Colorectal cancer is a type of cancer that is more commonly diagnosed in elderly people. Several lifestyle and environmental factors play a crucial role in increasing the risk of developing this type of cancer. Research has shown that up to 80% of colorectal cancer cases can be prevented or caused by dietary habits.
According to research, it is widely believed that diet plays a significant role in the onset of colorectal cancer, particularly in Western-type diets. In 2007, the World Cancer Research Fund and the American Institute for Cancer Research published a comprehensive global review titled ‘Food, Nutrition, Physical Activity and the Prevention of Cancer’, which supported this notion. The review, which was based on mainly prospective cohort studies, concluded that the consumption of red and processed meat, a high intake of alcoholic beverages, excess body and abdominal fat, and factors that contribute to greater adult attained height or its consequences are all causes of colorectal cancer.
Additionally, it was found that foods containing dietary fiber, garlic, milk, and calcium probably protect against this cancer. Furthermore, non-starchy vegetables, fruits, fish, and foods containing folate, vitamin D, or selenium may offer protection against colorectal cancer, while foods containing animal fats or sugar may cause it. A study also showed that re-occurrence of colorectal cancer was significantly higher in individuals who consumed a Westernized diet compared to those who ate diets with more fiber and less fat and sugar.10
Regular exercise and maintaining a healthy weight are crucial factors that can help prevent cancer and reduce the chances of its recurrence. Conversely, the consumption of tobacco and alcohol has been linked to a higher risk of colon cancer and other types of cancer. If someone experiences long-term stomach issues or “bloody stool,” it is essential to seek medical attention. As a person ages, the likelihood of requiring a colonoscopy increases.9
Screening is the process of checking for cancer or pre-cancer in individuals who do not exhibit any symptoms of the disease. Regular screening for colorectal cancer is one of the most effective ways to prevent the occurrence of the disease. The growth of abnormal cells into polyps usually takes about 10 to 15 years before they develop into colorectal cancer. Regular screening helps in identifying and removing most polyps before they become cancerous. Screening can also detect colorectal cancer at an early stage when it is small and simpler to treat.
Starting at the age of 45 or older, it’s recommended that individuals undergo screening for colorectal cancer. There are several types of tests available, and it’s important to consult with a healthcare provider about the options. No matter which tests are chosen, the most important thing is to get tested. If there is a strong family history of colorectal polyps or cancer, it’s essential to talk with a doctor about the risks. It may also be beneficial to consider genetic counseling to review the family medical history and determine the likelihood of having a family cancer syndrome.11
Prevention and Lynch syndrome
Lynch syndrome is a genetic condition that increases the risk of developing cancer up to 80%. It is common for affected individuals to develop multiple cancers in their lifetime. If someone is diagnosed with Lynch syndrome, it is crucial to have their family members tested, as the condition is dominantly inherited with a 50% chance of passing it on. It is estimated that about 1,200,000 people in the United States have Lynch syndrome.
Early diagnosis of Lynch syndrome is crucial because it allows for predicting illness and monitoring changes, such as precancerous conditions, that can lead to cancer development. Identifying Lynch syndrome is especially significant when it comes to cancer treatment. For example, a malfunctioning MMR repair mechanism causes tumor instability (microsatellite instability, MSI), based on which effective immunotherapy used for MSI cancers can be used in cancer treatment. In addition, recent studies suggest that this characteristic of Lynch syndrome cancers would offer the possibility of developing a cancer-preventing vaccine.
The diagnosis of Lynch syndrome leads to personalized treatment and regular monitoring for the patient and their family members who have inherited the syndrome.
DiagMMR is a test that can detect Lynch syndrome. This technology helps to identify Lynch syndrome at an early stage and target expensive monitoring and treatment to people who are at real risk, both in the general population and in Lynch syndrome families. DiagMMR technology plays an important role in preventing cancer, significantly reducing healthcare costs and saving lives.
References
[1] Colorectal cancer screening – HUS patient information
[2] What Is Colorectal Cancer? – Centers for Disease Control and Prevention.
[3] What is cancer? – Cancer Society of Finland
[4] Colorectal Cancer Risk Factors – American Cancer Society
[5] Key Statistics for Colorectal Cancer – American Cancer Society
[6] Periytyvä syöpäalttius – Lääkärikirja Duodecim
[7] Cancer genetics – Cancer Society of Finland
[8] Peltomäki P, Nyström M, Mecklin J-P, Seppälä TT, Lynch syndrome genetics and clinical implications, Gastroenterology (2023), DOI: 10.1053/j.gastro.2022.08.058.
[9] Suolistosyöpä – Lääkärikirja Duodecim
[10] Nyström M, Mutanen M. Diet and epigenetics in colon cancer. World J Gastroenterol 2009; 15(3): 257–263, DOI: 10.3748/wjg.15.257.
[11] Can Colorectal Cancer Be Prevented? – American Cancer Society