95% of all rectal cancers are adenocarcinomas. Adenocarcinoma is a cancer that arises from the glandular lining, or mucous membranes of the colon, rectum and appendix. Colorectal adenocarcinoma is the third most common cancer in men and women and second leading cause of death for both men and women in the United States. As a group, colorectal cancers are the most common gastrointestinal (GI) carcinomas and have the best prognosis of all GI cancers. Rectal cancer is a special case of colorectal cancer, since it occurs in the last part of the large intestine, the rectum, which is located within the bony confines of the pelvis. Since the pelvis is a tighter space with many other important organs, such as the bladder and reproductive organs, treatment of rectal cancer presents some unique challenges to curing this disease.
What are the risk factors for rectal cancer?
It is important to understand that while a family history is considered a risk factor for the development of colorectal cancer, greater than 75% of colon and rectal cancers occur in people with no family history. Colorectal cancer may occur at any age, although over 90% of the patients are over age 40 at diagnosis. Following this the risk doubles every ten years. In addition to age, other high risk factors include:
- African American
- Males show a slight predominance
- Personal risk factors:
- Family history of polyps or cancer
- Personal history of colonic polyps
- Inflammatory Bowel Disease
- Chronic ulcerative colitis
- Chronic Crohn's colitis
- Personal history of cancer, especially:
- Lifestyle/environmental risks
- Tobacco consumption
- Alcohol consumption
- Physical inactivity
- Diet high in red meats & animal fats
- Low fiber diet
- Inheritable genetic conditions
- Familial Adenomatous Polyposis
- Herediary Non-Polyposis Colon Cancer
Approximately 10% of cases are linked to insufficient activity. The risk for alcohol appears to increase at greater than one drink per day. There is no absolute risk factor for the development of colorectal cancer, therefore, even though living a healthy lifestyle is helpful, it cannot prevent the development of colorectal cancer entirely. It is for this reason that colorectal cancer screening through colonoscopies is advised.
What causes rectal cancer?
Many colorectal cancers are thought to arise from adenomatous polyps in the rectum. It is believed that nearly all colon and rectal cancer begins in benign polyps. These pre-cancerous growths occur on the bowel wall eventually increasing in size and becoming cancer. This sequence can be averted through a preventative colonoscopy.
What are the symptoms of rectal cancer?
It is important to understand that the most common symptom of colorectal cancer and polyps are no symptoms at all. For this reason it is important that colorectal cancer screening begins at the age of 50 or starting at the age of 40 for individuals who are experiencing rectal bleeding or have a first-degree relative (parent or sibling) with colon cancer or polyps should start their colon cancer screening at the age of 40. The goal is to identify the potential for disease or the condition early when it is easier to prevent or cure.
Colorectal cancer is known as a "silent" disease, because many people do not develop symptoms, such as bleeding or abdominal pain until the cancer is difficult to cure. In fact, the possibility of curing patients after symptoms develop is only about 50%. On the other hand, if colorectal cancer is found and treated at an early stage, before symptoms develop, the opportunity to cure is 80% or better. Late symptoms of rectal cancer include: blood in the stool, change in bowel habits including narrowing of the stool, constipation, diarrhea, rectal pain, unexplained weight loss.
How is rectal cancer diagnosed?
The majority of the time, the diagnosis of early rectal cancer is through a colonoscopy. The symptoms of rectal cancer to watch out for include any change in bowel habits such as constipation, narrowing of the stools or diarrhea and any blood in the stools. A colonoscopy will often be necessary to obtain a tissue biopsy and confirm the diagnosis of a more advanced colorectal cancer as well, although the initial diagnosis may be made with another modality, such as a CT scan. Additional studies such as a CT scan and a PET scan will typically be done to stage the cancer, especially to evaluate whether the cancer has spread to the lymph nodes or other organs, such as the liver.
Both colon and rectal cancers are adenocarcinomas and have a similar pattern of spread to lymph nodes. The treatment of rectal cancers differs slightly from colon cancer because the rectum is located in the bony confines of the pelvis where there are many closely spaced organs in both men and women. Additionally for the rectum, as the last segment of the large intestine, preservation of the anal sphincters is an important consideration when planning a surgical intervention. Sphincter-sparing surgeries are an important part of the colorectal surgeon’s armamentarium in the fight against rectal cancers while maintaining quality of life for patients.
Rectal Adenocarcinoma Treatment
In the early stages of rectal cancer, like colon cancer, surgery alone can be curative. In more advanced rectal cancer, where the cancer has spread to the lymph nodes, chemotherapy and radiation are generally advised.
Pre-treatment staging is important to optimize overall recovery and likelihood of a cure. This will typically consist of a combined PET scan/ CT scan, rectal ultrasound or MRI. The purpose of these tests is to determine, to the best our technologic ability, two factors. First, how deeply into the bowel wall has the primary cancer invaded and if it has invaded directly into adjacent organs such as the prostate in men or the vagina in women. Second, whether the cancer has developed the ability to spread, or metastasize to local lymph nodes. If the primary tumor has invaded through all the layers of the rectal wall, or has evidence of spread to local lymph nodes, neo-adjuvant (before surgery) combined chemotherapy and radiation is generally advised. If the pre-treatment staging indicates the cancer is an early stage, patients may proceed directly to surgery.
Surgery involves removal of all or part of the rectum, usually about 12 inches, along with its associated blood supply and lymph nodes. This is called a total mesorectal excision or TME. This is followed by reconnection of the bowel to re-establish continuity, which is called an anastomosis. If the patient has had neo-adjuvant chemotherapy and radiation a diverting loop ileostomy is typically performed to protect the newly reconnected bowel. Once the anastomosis has healed properly, the ileostomy is reversed or closed.
In some cases the rectal cancer is so low that it invades into the muscles responsible for control over bowel movements, the sphincter muscles. In those cases, it is necessary to remove the anus with the rectum to ensure that the entire cancer is removed. Under those circumstances the surgeon will also create a permanent colostomy.
What is the prognosis of rectal cancer?
It is to the patient’s advantage to have the operation performed by a colon and rectal surgeon because we are experienced in performing rectal surgeries and therefore our ability to reconnect the bowel and perform sphincter-sparing surgeries is better than those with less experience with these technically demanding cases. Surgery can be accomplished with a traditional, open approach or with some of the newer minimally-invasive surgeries such as laparoscopic and robotic techniques. The operation is performed on an inpatient basis and patients typically are in the hospital for 5 days after surgery.
As in colon cancer, it is important to remove all of the cancer in one piece along with a rim of surrounding healthy tissue to ensure that none of the cancer is left behind. The lymph nodes are also removed and evaluated. Although pre-treatment staging has been done, the pathologist must still determine how deeply into the rectal wall the cancer has invaded, that all of the primary cancer has been removed and if the cancer has developed the ability to spread in a dis-continuous fashion or metastasize away from the primary tumor. If the pathologist confirms that a rectal cancer is in the early stages, surgery may be all that is required for optimal treatment of the cancer. In patients who have already had neo-adjuvant chemotherapy and radiation the pathologist will also determine the level of response to the chemotherapy and radiation. Finally, in some cases, patients who appeared to have an early stage rectal cancer will be found by the pathologist to have evidence of cancer spread to the lymph nodes. In this event, the radiation and chemotherapy is administered after recovery from surgery.
Rectal cancer requires surgery to remove the affected rectum in nearly all cases for complete cure. Between 80-90% are restored to normal health if the cancer is detected and treated in the earliest stages. The cure rate drops to 50% or less when diagnosed in the later stages. Thanks to modern surgical techniques, particularly in the hands of a board certified colon and rectal surgeon, less than 5% of all colorectal cancer patients require a creation of a permanent end colostomy.