Rectal Cancer Overview
The rectum is the lower part of the colon that connects the large bowel to the anus. The rectum’s primary function is to store formed stool in preparation for evacuation. Like the colon, the 3 layers of the rectal wall are as follows:
In addition to these 3 layers, another important component of the rectum is the surrounding lymph nodes (also called regional lymph nodes). Lymph nodes are part of the immune system and assist in conducting surveillance for harmful materials (including viruses and bacteria) that may be threatening the body. Lymph nodes surround every organ in the body, including the rectum.
Of the 150,000 cases of colorectal cancer diagnosed each year in the United States, more than 40,000 people are diagnosed with rectal cancer. The most common type of rectal cancer is adenocarcinoma, which is a cancer arising from the mucosa. Cancer cells can also spread from the rectum to the lymph nodes on their way to other parts of the body.
Like colon cancer, the prognosis and treatment of rectal cancer depends on how deeply the cancer has invaded the rectal wall and surrounding lymph nodes. However, although the rectum is part of the colon, the location of the rectum in the pelvis poses additional challenges in treatment when compared with colon cancer.
This article only discusses issues related to rectal adenocarcinoma.
Rectal Cancer Causes
Rectal cancer usually develops over several years, first growing as a precancerous growth called a polyp. Some polyps have the ability to turn into cancer and begin to grow and penetrate the wall of the rectum.
The actual cause of rectal cancer is unclear. However, the following are risk factors for developing rectal cancer:
Family history is a factor in determining the risk of rectal cancer. If a family history of colorectal cancer is present in a first-degree relative (a parent or a sibling), then endoscopy of the colon and rectum should begin 10 years before the age of the relative’s diagnosis or at age 50 years, whichever comes first.
An often forgotten risk factor, but perhaps the most important, is the lack of screening for rectal cancer. Routine cancer screening of the colon and rectum is the best way to prevent rectal cancer.
Rectal Cancer Symptoms
Rectal cancer can cause many symptoms that require a person to seek medical care. However, rectal cancer may also be present without any symptoms, underscoring the importance of routine health screening. Symptoms to be aware of include the following:
When to Seek Medical Care - Questions to Ask the Doctor
If a person has been diagnosed with rectal cancer, the doctor should be asked the following questions:
Exams and Tests
Appropriate colorectal screening leading to the detection and removal of precancerous growths is the only way to prevent this disease. Screening tests for rectal cancer include the following:
Exams and Tests continued...
If rectal cancer is suspected, the tumor can be physically detected through either digital rectal examination (DRE) or endoscopy.
Because the depth of the cancer’s growth into the rectal wall is important in determining treatment, an endoscopic ultrasound (EUS) may be performed during endoscopy. An endoscopic ultrasound uses an ultrasound probe at the tip of an endoscope that allows a doctor to see how deeply the cancer has penetrated. In addition, a doctor can measure the size of the lymph nodes around the rectum during an endoscopic ultrasound. Based on the size of the lymph nodes, a good prediction can be made as to whether the cancer has spread to the lymph nodes.
Once an abnormality is seen with endoscopy, a biopsy specimen is obtained using the endoscope and sent to a pathologist. The pathologist can confirm that the abnormality is a cancer and needs treatment. A person may experience small amounts of bleeding after a biopsy is performed. If this bleeding is heavy or lasts longer than a few days, a doctor should be notified immediately.
A chest x-ray and a CT scan of the abdomen and pelvis are most likely performed to see whether the cancer has spread further than the rectum or surrounding lymph nodes.
Routine blood studies are performed to assess how a person might tolerate the upcoming treatment.
In addition, a blood test called CEA (carcinoembryonic antigen) is obtained. The CEA is often produced by colorectal cancers and can be a useful gauge of how the treatment is working. After the treatment, the doctor may regularly check the CEA level as one indicator of whether the cancer has returned. However, checking the CEA level is not an absolute test for colorectal cancers, and other conditions may cause a rise in the CEA level. Likewise, a normal CEA level is not a guarantee that the cancer is no longer present.
Rectal Cancer Treatment - Medical Treatment
The treatment and prognosis of rectal cancer depend on the stage of the cancer, which is determined by the following 3 considerations:
The stages of rectal cancer are as follows:
Localized rectal cancer includes stages I-III. Metastatic rectal cancer is stage IV.
The goals of treating localized rectal cancer are to ensure the removal of all the cancer and to prevent a recurrence of the cancer, either near the rectum or elsewhere in the body.
If stage I rectal cancer is diagnosed, then surgery is likely to be the only necessary step in treatment. The risk of the cancer coming back after surgery is low, and, therefore, chemotherapy is not usually offered.
Sometimes, after the removal of a tumor, the doctor discovers that the tumor penetrated into the mesorectum (stage II) or that the lymph nodes contained cancer cells (stage III). In these cases, chemotherapy and radiation therapy are offered after recovery from the surgery to reduce the chance of the cancer returning. Chemotherapy and radiation therapy given after surgery is called adjuvant therapy.
If the initial exams and tests show a person to have stage II or III rectal cancer, then chemotherapy and radiation therapy should be considered before surgery. Chemotherapy and radiation given before surgery is called neoadjuvant therapy. This therapy lasts approximately 6 weeks. Neoadjuvant therapy is performed to shrink the tumor so it can be more completely removed by surgery. In addition, a person is likely to tolerate the side effects of combined chemotherapy and radiation therapy better if this therapy is administered before surgery rather than afterward. After recovery from the surgery, a person who has undergone neoadjuvant therapy should meet with the oncologist to discuss the need for more chemotherapy.
If the rectal cancer is metastatic, then surgery and radiation therapy would only be performed if persistent bleeding or bowel obstruction from the rectal mass exist. Otherwise, chemotherapy alone is the standard treatment of metastatic rectal cancer. At this time, metastatic rectal cancer is not curable. However, average survival times for people with metastatic rectal cancer have lengthened over the past several years because of the introduction of new medications.
The following chemotherapy drugs may be used at various points during therapy:
Medications are available to alleviate the side effects of chemotherapy and antibody treatments. If side effects occur, an oncologist should be notified so that they can be addressed promptly.
Surgical removal of a tumor is the cornerstone of curative therapy for localized rectal cancer. In addition to removing the rectal tumor, removing the fat and lymph nodes in the area of a rectal tumor is also necessary to minimize the chance that any cancer cells might be left behind.
However, because the rectum is in the pelvis and is close to the anal sphincter (the muscle that controls the ability to hold stool in the rectum), rectal surgery can be difficult. With more deeply invading tumors and when the lymph nodes are involved, chemotherapy and radiation therapy are usually included in the treatment course to increase the chance that all microscopic cancer cells are removed or killed.
Four types of surgeries are possible, depending on the location of the tumor in relation to the anus.
Radiation therapy uses high-energy rays that are aimed at the cancer cells to kill or shrink them. For rectal cancer, radiation therapy may be used either before surgery (neoadjuvant therapy) or after surgery (adjuvant therapy), usually in conjunction with chemotherapy.
The goals of radiation therapy are as follows:
Typically, radiation treatments are given daily, 5 days a week, for up to 6 weeks. Each treatment lasts only a few minutes and is completely painless; it is similar to having an x-ray film taken.
The main side effects of radiation therapy for rectal cancer include mild skin irritation, diarrhea, rectal or bladder irritation, and fatigue. These side effects usually resolve soon after the treatment is complete.
Chemoradiation is often given for stages II and III rectal cancer. Preoperative chemoradiation is sometimes performed to decrease the size of the tumor.
Next Steps - Follow-up
Because a risk exists of rectal cancer coming back after treatment, routine follow-up care is necessary. Follow-up care usually consists of regular visits to the doctor’s office for physical exams, blood studies, and imaging studies.
In addition, a colonoscopy is recommended 1 year after a diagnosis of rectal cancer. If the findings from the colonoscopy are normal, then the procedure can be repeated every 3 years.
Appropriate colorectal screening leading to the detection and removal of precancerous growths is the only way to prevent this disease. Screening tests for rectal cancer include fecal occult blood test and endoscopy.
If a family history of colorectal cancer is present in a first-degree relative (a parent or a sibling), then endoscopy of the colon and rectum should begin 10 years before the age of the relative’s diagnosis or at age 50 years, whichever comes first.
The outlook for recovery from rectal cancer is unique for each individual. Many factors are involved when considering the chance of survival after rectal cancer treatment.
Long-term survival generally depends upon the stage of the cancer at the time of diagnosis and treatment.
According to stage, the following approximations of the likelihood of survival 5 years after treatment are as follows:
Support Groups and Counseling
Being diagnosed with cancer is a physically and emotionally trying experience. Many avenues of support exist within the local community and beyond, both for people diagnosed with cancer and for their family and friends. The American Cancer Society provides information on local support groups. In addition, social workers, counselors, psychiatrists, and clergy can also be helpful in providing information and companionship through the difficult times caused by a cancer diagnosis