Rectal Cancer specifically forms in the tissues of the rectum (roughly the last 30cm of the large intestine closest to the anus). The rectum starts at the end of the final segment of your colon and ends when it reaches the short, narrow passage leading to the anus. The rectum is part of the body’s digestive system, where food is processed for its nutrients and waste is excreted from the body. Rectal cancer and cancer inside the colon (colon cancer) are often referred to together as “colorectal cancer”.
Similar to how bowel cancer develops, healthy cells in the rectum develop changes (called mutations) in their instructions (known as DNA). These mutations tell the cells to grow uncontrollably and to continue living after healthy cells would otherwise die. The rapidly growing cells then start form a tumour, called a polyp. With time, the cancer cells can grow to invade healthy tissue nearby, as well as travelling (metastasise) to other parts of the body.
Rectal Neuroendocrine Tumours (NETs) are amongst the most common intestinal NET (about 14%) and are the most uncommon colorectal cancer (less than 1%). Around half of cases are diagnosed during tests or treatments for other conditions. Rectal NETs can cause bleeding, constipation, or pain on defaecation (opening your bowels), but they may cause no symptoms at all – which may delay diagnosis.
Signs and symptoms of rectal cancer include:
- A change in bowel habits, such as diarrhoea, constipation or more-frequent bowel movements
- Dark maroon or bright red blood in stool (faeces or poo)
- Narrow stool (faeces or poo)
- A feeling that your bowel doesn’t empty completely
- Abdominal pain
- Unexplained weight loss
- Weakness or fatigue
If you experience any of these symptoms or have concerns, please contact your general practitioner (GP).
It is estimated that 4,670 Australians were diagnosed with rectal cancer in 2022. Males are more likely to be diagnosed with rectal cancer, with 2,829 men diagnosed in 2022 compared to 1,841 women. A person’s chance of living 5 years with this cancer has increased from 53% (in 1989–1993) to 70.5%.
Factors that may increase the risk of rectal cancer are the same as those that increase the risk of colon cancer. Risk factors include:
- Older age. Rectal cancer can be diagnosed at any age, but most people with this type of cancer are older than 50.
- A personal or family history of colorectal cancer or polyps.
- Inflammatory bowel disease, such as ulcerative colitis and Crohn’s disease.
- Inherited syndromes increase rectal cancer risk, including FAP (Familial adenomatous polyposis) and Lynch syndrome.
- Eating a diet low in vegetables and high in red meat, particularly when the meat is charred or well done.
- Too little exercise. Getting regular physical activity may reduce your risk of cancer.
- People with poorly controlled type 2 diabetes may have an increased risk of rectal cancer.
- Obese people have an increased risk of rectal cancer when compared with people considered at a healthy weight.
- People who smoke may have an increased risk of rectal cancer.
- Regularly drinking more than three alcoholic beverages a week may increase your risk of rectal cancer.
- Radiation therapy directed at the abdomen to treat previous cancers may increase the risk of rectal cancer.
Rectal cancer can be found during a screening test for colon cancer or it may be suspected based on your symptoms. Tests and procedures used to confirm the diagnosis include:
- Digital rectal exam: An exam of the rectum. The doctor or nurse inserts a lubricated, gloved finger into the lower part of the rectum to feel for lumps or anything else that seems unusual.
- Using a scope to examine the inside of your colon and rectum (colonoscopy). Colonoscopy uses a long, flexible tube attached to a video camera and monitor to view your colon and rectum. If cancer is found in your rectum, your doctor may recommend examining your colon in order to look for additional suspicious areas.
- Removing a sample of tissue for testing (biopsy). If any suspicious areas are found during your colonoscopy, your doctor can pass surgical tools through the tube to take tissue samples (biopsies) for analysis and remove polyps.
Any tissue samples collected will then sent to a lab to be examined by doctors who specialise in analysing blood and body tissues (pathologists). Tests can determine whether the cells are cancer, whether they’re aggressive and which genes in the cancer cells are abnormal. Your doctor uses this information to understand your prognosis and determine your treatment options.
Once you’re diagnosed with rectal cancer, the next step is to determine the cancer’s extent (stage). The stage of your cancer helps determine your prognosis and your treatment options. Tests that might be performed to determine your stage include blood tests (to look at levels of tumour markers in your blood or to measure organ function) and body scans (known as CT or MRI scans) to see if the cancer has spread to other parts of your body.
Rectal cancer treatment often involves a combination of therapies. When possible, surgery is used to cut away the cancer cells. Other treatments, such as chemotherapy and radiation therapy, may be used after surgery to kill any cancer cells that remain and reduce the risk that cancer will return.
If surgeons are concerned that the cancer can’t be removed completely without hurting nearby organs and structures, your doctor may recommend a combination of chemotherapy and radiation therapy as your initial treatment. These combined treatments may shrink the cancer and make it easier to remove during an operation.
Rectal cancer is often treated with surgery to remove the cancer cells. Which operation is best for you depends on your particular situation, such as the location and stage of your cancer, how aggressive the cancer cells are, your overall health, and your preferences.
Chemotherapy uses drugs to destroy cancer cells. For rectal cancer, chemotherapy might be recommended after surgery to kill any cancer cells that might remain. Chemotherapy combined with radiation therapy might also be used before an operation to shrink a large cancer so that it’s easier to remove with surgery. Chemotherapy can also be used to relieve symptoms of rectal cancer that can’t be removed with surgery or that has spread to other areas of the body.
Radiation therapy uses powerful energy sources, such as X-rays and protons, to kill cancer cells. In people with rectal cancer, radiation therapy is often combined with chemotherapy that makes the cancer cells more likely to be damaged by the radiation. It can be used after surgery to kill any cancer cells that might remain. It can also be used before surgery to shrink a cancer and make it easier to remove.
Targeted drug therapy
Targeted drug treatments focus on specific abnormalities present within cancer cells. By blocking these abnormalities, targeted drug treatments can cause cancer cells to die. Targeted drugs are usually combined with chemotherapy. Targeted drugs are typically reserved for people with advanced rectal cancer.
Immunotherapy is a drug treatment that uses your immune system to fight cancer. Your body’s disease-fighting immune system may not attack your cancer because the cancer cells produce proteins that help them hide from the immune system cells. Immunotherapy works by interfering with that process. Immunotherapy is usually reserved for advanced rectal cancer.
Australia has a National Bowel Cancer Screening Program (for large bowel cancer, which includes the rectum) that provides free and easy bowel cancer tests for individuals aged over 50.
The program’s aim is early detection of bowel cancer in individuals before any serious symptoms appear. The screening test is called a Faecal Occult Blood Test (FOBT), which detects blood in stool samples. The test does not diagnose bowel cancer, but can find tiny traces of blood in stool samples, which may be an early sign of disease. The results will indicate if a further test is needed to rule out bowel cancer.
Research has shown screening for bowel cancer, using the FOBT, can reduce bowel cancer deaths by 15 to 25%.
You can learn more about the National Bowel Cancer Screening Program by clicking here.
Avoiding the risk factors listed above can help to reduce the chance of developing rectal cancer. Protective steps include quitting smoking, doing physical activity and maintaining a healthy body weight. This includes changes in lifestyle habits, such as having a diet high in fibre, eating fresh fruit and vegetables and cutting down on processed meat.