Both colon cancers and rectal cancers affect the large intestine, so the symptoms, screening tools, prevention, risk factors, and diagnosis are the same for both. The treatment, however, could be different.
The rectum is the final part of the colon; it is about 6 inches long, and its main function is to store stool until a bowel movement can be made. A cancer of the colon can start anywhere in the colon, which is about five feet long and absorbs water from stool.
If the rectum is removed, a person may no longer have as much an ability to hold bowel movements, resulting in frequent, urgent trips to the bathroom.
“Any cancer of the rectum, we treat a little bit differently than cancer of the colon, for the reason that because it sits in the pelvis, which is essentially a bony ice cream cone, it makes any surgery in this area much more challenging,” Dr. Kyle Cologne, a professor of clinical surgery at the Keck School of Medicine at USC, told SurvivorNet in a previous conversation. “This is also why for rectal cancer we may use, much more so than colon cancer, things like chemotherapy, potentially even before surgery, radiation, and these all are part of your diagnosis that your surgeon should talk to you about.”
When you have a colonoscopy, the gastroenterologist performing the procedure is looking at the inside of your colon and rectum to detect growths and to pinpoint their location in the colon or rectum.
Where the cancer is located (whether it is in the colon or rectum) is important because the rectum does not have the same protective outer layer (called the serosa) as the colon, so it may be easier for a tumor to break through and begin to spread locally in the body. This also means that rectal cancer is more likely to recur after treatment compared to colon cancer. In addition, because of the rectum’s important function as a storage organ for stool, surgery to remove the rectum causes significant changes in quality of life when compared to surgery to remove part of the colon. This changes the considerations to select tools such as chemotherapy and radiation in addition to, or sometimes even instead of, surgery.
“With rectal cancers, they come in all shapes and sizes,” says Dr. Cologne. “And what I like to tell patients is, it’s like buying a house. It’s all about location. So, tumors that are in the upper rectum are much easier to treat than tumors in the lower rectum.”
So, what does this mean when it comes to treating rectal cancer? Before making treatment decisions, your medical team will need to stage the disease to determine the extent of the tumor. The staging for rectal cancer involves having chest and abdominal CT scans and an MRI scan of the pelvis. These scans can help determine:
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Some tumors may be localized near the verge of the anus, infiltrating the anal sphincter (the muscle that holds stool inside the rectum and enables voluntary bowel movements). In this situation, a combination of chemotherapy and radiation may be warranted before surgery. This is called neoadjuvant therapy and is used to try to shrink a tumor and kill off lymph nodes in the area that are affected by the cancer. If the neoadjuvant treatment is successful, a person may be able to go on to have surgery with something called sphincter preservation, which will allow patients to continue having regular bowel movements.
In some cases, neoadjuvant therapy works so well that the tumor disappears and surgeons may recommend a watch-and-wait strategy instead of surgery. This approach has gained traction over the past decade as new medical evidence supports this option for certain patients. Major cancer centers such as Memorial Sloan Kettering and MD Anderson support using this approach for patients who are eligible.
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For this strategy to work, however, the therapy and subsequent follow-ups must be performed in specialized cancer centers under the surveillance of experts in the field. Patients should also be active partners with the health professionals they are working with, speaking up and asking questions about treatments or other issues they may be concerned about. For the watch-and-wait approach to work, patients must also adhere to regular follow-up visits, which will likely including tests such as MRI scans and colonoscopies.
Patients who are undergoing surgery for colon or rectal cancer should have a candid conversation with their doctors about potential side effects. Side effects will depend largely on how much of the colon had to be removed and exactly where the cancer was located, but many of these procedures can be carried out with minimal long-term effects.
Because these surgeries operate on a very delicate area and there is the potential for side effects — in things like bowel function as well as sexual function — experts in the field stress the importance of seeing a colorectal surgeon certified by the American Board of Colon and Rectal Surgery.
“[Potential side effects are] one of the reasons that we usually recommend that people see a rectal cancer specialist,” Dr. Heather Yeo, a colorectal cancer surgeon at Weill Cornell Medical Center, told SurvivorNet. “…the area of the rectum you have to take out sits right on top of a bed of nerves, and you can almost always see those nerves pretty clearly, but sometimes the cancers are stuck to them, so you really want a specialist there to try and preserve as much of the nerve structure as they can [because] there is the potential for a long term sexual dysfunction. Not only sexual dysfunction, but the patients can have a long term dysfunction from a urinary standpoint, and even if they’ve been put back together, they can have problems with their bowels afterwards.”
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