What is Rectal Cancer?

Colon and rectal cancers, when combined, form the third most commonly diagnosed cancer and the second deadliest type in the United States. Rectal cancer, in particular, has different environmental and genetic risk factors compared to colon cancer. The normal lining of the rectum changing into an abnormal growth and then into invasive cancer typically takes about 10 to 15 years. This process involves a variety of genetic changes, some of which can be inherited and some can be acquired. The main factors that can affect the outcome of rectal cancer include how the cancer responds to treatment before surgery and how far the cancer has spread, as determined by tests.

When checking for rectal cancer, doctors usually begin by asking about your medical history and carrying out a physical examination, which includes a manual check of the rectum. Then, a special instrument known as a sigmoidoscope is used to examine the rectum internally. This helps to gauge how far the cancer is from the anus and also allows the doctor to take tissue samples for further testing. Once rectal cancer is confirmed through these samples, an MRI scan or an ultrasound of the rectum can help to find out if the cancer has spread locally to nearby tissues or lymph nodes. A CT scan of the chest, abdomen, and pelvis can help to find out if the cancer has spread to other parts of the body.

Assessing the cancer from various angles, through medical, radiation, and surgical specialists, is crucial in deciding the most effective combination of chemotherapy, radiotherapy, and potentially surgery to optimize the likelihood of a cure, especially in high-risk patients. Even in cases where the cancer has spread to the liver and lungs, or returned after treatment, there is still a potential for a cure with the right combination of treatments. If surgery is not an option, palliative therapy can be used to manage symptoms, enhance the quality of life, and extend the life expectancy.

What Causes Rectal Cancer?

Most cases of colorectal cancer, which includes rectal cancer, occur randomly and aren’t inherited (70%), and usually affect people above 50 years old. Only a small portion (10%) actually inherit the disease, which carries a higher risk for people under 50, while 20% of cases show a tendency to run in families without a clear inherited pattern. Familial adenomatous polyposis (a condition where many polyps form in the colon and rectum) and Lynch syndrome (a condition that increases the risk of many types of cancer) account for about 5% of all colorectal cancer cases.

There are certain risk factors that can increase your likelihood of developing colorectal cancer. These include: a personal or family history of colorectal cancer or certain types of polyps, and inflammatory bowel diseases like ulcerative colitis and Crohn’s disease that affect the rectum. If you’ve been diagnosed with ulcerative colitis, your risk of getting colorectal cancer increases over time, with up to a 30% chance of developing it in the fourth decade after diagnosis. There’s also an increased risk of rectal cancer in men who have had radiation treatment for prostate cancer.

Lifestyle and environmental factors can also influence your risk of colorectal cancer. For example, being obese, consuming red/processed meat, using tobacco, consuming alcohol, androgen deprivation therapy (a type of hormone therapy to treat certain cancers), and gallbladder removal are associated with a higher risk of colon cancer, not necessarily rectal. On the plus side, being physically active, eating a diet rich in fruits, vegetables, fiber, resistant starch, and fish, taking certain vitamin supplements and drugs like aspirin and non-steroidal anti-inflammatory drugs, hormonal replacement therapy in postmenopausal women, statins (medicine for lowering cholesterol), bisphosphonates (bone-strengthening drugs), and angiotensin inhibitors (blood pressure medications) have been found to reduce the risk of both colon and rectal cancer. One study even found that taking aspirin can reduce the risk of developing polyps and cancer in patients with Lynch syndrome. However, this association hasn’t been thoroughly studied in the general population.

Risk Factors and Frequency for Rectal Cancer

Colorectal cancer impacts a large number of people in the United States, with around 135,439 new cases each year. Out of these, 30% or 39,910 cases are due to rectal cancer. However, the exact mortalities from rectal cancer are unclear, as some deaths get wrongly classified as colon cancer deaths. When combined, colorectal cancers are the second leading cause of cancer-related deaths in the United States, taking an estimated 50,260 lives each year.

Interestingly, around 18% of rectal cancer cases occur in individuals under 50 years of age, and these cases often have a more advanced stage and unfavorable prognosis. Even as the overall rate of colorectal cancer has been falling by 3% annually since 2004, the rate has been increasing by 2% each year among screened young adults. This uptick is mainly due to increases in left-sided colon cancer and rectal cancer.

The occurrence of colorectal cancer is higher in developed countries compared to developing ones. People with a lower socioeconomic status have a greater risk of contracting this type of cancer, and this risk is especially high for rectal cancer. Poor health habits and limited access to healthcare are believed to be the main reasons for this. White Americans have an average lifetime risk of 5% for colorectal cancer, but the risk is higher for men than women, and for African Americans as compared to non-Hispanic whites. Fortunately, the mortality rate for colorectal cancer in the U.S. has dropped by 51% between 1975 and 2014 due to better detection and treatment methods. According to the National Cancer Institute, approximately 65% of patients treated for colorectal cancer are expected to be alive after five years.

Signs and Symptoms of Rectal Cancer

Colorectal cancer (CRC), can present itself in multiple ways. The vast majority (80%) are diagnosed during a colonoscopy when there are signs or symptoms that cause concern. Some people (11%) are diagnosed during a regular check-up when there are no symptoms, while 7% of diagnoses happen unexpectedly during emergency surgeries for unrelated issues. It’s worth noting that people who are diagnosed during a routine screening often have an earlier stage of the disease compared to those found during surgery.

People are prompted to undergo diagnostic colonoscopy for a few common reasons, including bleeding from the rectum (37%), abdominal pain (34%), and anemia (23%). Emergency surgeries usually occur due to obstruction (57%), inflammation of the peritoneum (25%), or perforation (18%).

Symptoms vary based on where the tumor is located in the rectosigmoid, which is the last part of the colon. These can be:

Change in bowel habits
Bleeding from the rectum
Painful bowel movements
Leakage diarrhea
Constipation

Sometimes, the first signs of cancer are symptoms of metastatic disease, meaning cancer that has spread to other parts of the body. The form these symptoms take will depend on the organ affected. A physical check-up should look for any signs of excessive fluid in the abdomen, enlarged liver, and swollen lymph nodes, and also include a rectal exam to check for tumors.

Another important aspect of patient evaluation is to collect a thorough family history. This can help identify patterns that might suggest increased risk, which could influence the approach to monitoring and treatment.

Testing for Rectal Cancer

For patients newly diagnosed with rectal cancer, it’s standard to check for DNA mismatch repair/microsatellar status. This is a condition present in up to 13% of all unrelated cases of rectal cancer.

The first tests might involve the use of barium put into the rectum then X-rayed (a barium enema) or a CT scan of the colon. However, to get a tissue sample for further testing, an endoscopy is necessary. Specifically, a colonoscopy – a test which examines the entire length of the colon – will provide a full picture. A sigmoidoscopy – a test that only checks the lower part of the colon – is not a complete substitute but can be an effective screening tool in reducing the risk of colon cancer. There’s also a capsule endoscopy device, PILLCAM 2, approved by the Federal Drug Administration (FDA) for cases where a full colonoscopy can’t be completed. Other screenings and related recommendations will be provided in a separate article.

Typical lab tests may include complete blood count (CBC), iron panel, basic metabolic panel, liver function test, and coagulation tests, which help to plan treatment. The Carcinoembryonic antigen (CEA) – a type of protein – is also checked. If this is higher than five ng/mL it generally indicates a poor prognosis (outlook), but it is not always reliable for diagnosis, hence CEA is mainly used to check the effect of treatment and to monitor cancer recurrence.

Above all, CT scans of the chest, abdomen, and pelvis with intravenous (injected into a vein) and oral contrast are the generally preferred imaging test before any surgical action is taken. They are most helpful in identifying any distant spread of the disease. Other scan types like MRI and ‘triple-phase’ CT can be more effective at finding liver spread. However, using PET (a type of scan that uses radiation to create 3D color images of the functional processes in the body) to stage colon cancer before surgery isn’t routinely recommended. Any findings that suggest cancer has spread somewhere else in the body ought to be confirmed via a biopsy.

The precise location of the tumor, may it be low, middle, or high rectal cancer, is measured from the anal verge (the line separating the outside skin from the inner lining of the rectum) using a rigid sigmoidoscopy. The way to determine the exact location, size, and the risk of cancer spread requires precise imaging by transrectal ultrasonography (TRUS) and pelvic magnetic resonance imaging (MRI). These help doctors decide the best treatment approach: immediate surgery, radiation therapy, or combined chemotherapy and radiation. Both TRUS and MRI provide critical, complementary information although TRUS has more limitations in assessing cancer response after pre-operative treatment, while MRI has a more accurate display of the post-treatment anatomy.

Treatment Options for Rectal Cancer

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There are various conditions that can cause similar symptoms in our digestive system. If you’re experiencing discomfort, a doctor might consider the following potential causes:

Coeliac disease (a reaction to gluten)
Diarrhea
Diverticulosis (bulging pouches in the lining of your digestive system)
Food intolerance
Hemorrhoids (swollen veins in the rectum or anus)
Inflammatory bowel disease
Irritable bowel syndrome (IBS)
Radiation enteritis (inflammation of the intestines due to radiation therapy)

What to expect with Rectal Cancer

Colorectal cancer, when detected early, can be treated very effectively. The general survival rate after five years for rectal cancer is 67%, but various factors, primarily the stage of the cancer, can significantly alter this figure.

If the cancer is discovered when it’s in the localized stage (meaning it’s confined to a certain area), the survival rate drastically increases to 89%. If the cancer has spread to surrounding tissues, organs, or regional lymph nodes (which are small structures that work as filters for harmful substances), the 5-year survival rate is around 71%.

However, if the cancer has spread to distant areas of the body, a condition known as metastatic spread, the 5-year survival rate decreases significantly to 15%.

Possible Complications When Diagnosed with Rectal Cancer

Possible complications from rectal cancer may include a blockage in the bowel, the cancer returning or getting another colon or rectal cancer, and the cancer spreading to other parts of the body.

Common Complications:

Bowel obstruction
Recurring cancer
Developing another colo-rectal cancer
Metastatic disease (the cancer spreading to other parts of the body)

Preventing Rectal Cancer

The best way to fight colon and rectal cancers (commonly known as colorectal cancer) is to prevent them from developing and to find them early if they do develop. Factors that can increase your chances of developing these cancers include your age and your genetic history. Doctors generally recommend that people who are over the age of 50 get screened for colorectal cancer every 10 years. Screening can help detect the disease early when it’s easier to treat.