Rectal cancer is the same type of adenocarcinoma seen in colon cancer, but is located in the last 15 cm of the colon, which is known as the rectum. The rectum differs from the colon in that it is located deep in the pelvis and attached to the anus. These differences present treatment plans that can differ from colon cancer treatment. The rectum can receive radiation therapy, a modality generally not used in colon cancer. Also, the anus may need to be resected along with the rectum to ensure complete tumor removal, which can result in a permanent colostomy.
Symptoms of Rectal Cancer
Due to the proximity of the rectum to the anus, patients may be more likely to notice symptoms of rectal cancer. These symptoms may include bleeding, mucus discharge, irregular shape and size of bowel movements, unusual rectal pain and pressure, or fecal incontinence.
Rectal cancer is diagnosed by the pathology of a biopsy specimen. An accurate diagnosis is important due to the complex nature of treatments. If a cancer is very close to the anus, it is important to distinguish an anal canal cancer from a rectal cancer because they are treated differently.
Rectal Cancer Staging
Small rectal cancers can be treated by resection alone. Larger tumors are treated by adjuvant therapy, which means radiation therapy and chemotherapy prior to surgical excision. To properly determine the size of a tumor and its depth of penetration clinicians often rely on endorectal ultrasound. An endorectal ultrasound involves a small device that can be inserted through the anus allowing the tumor to be imaged. Valuable information obtained by endorectal ultrasound can assist in determining the need for adjuvant therapy.
Large rectal tumors are generally treated by 4-5 weeks of radiation therapy and chemotherapy. A radiation oncologist and a medical oncologist provide these treatments. Radiation treatments are administered at radiation oncology facility and generally given daily, 5 days a week, for 4-5 weeks duration. The chemotherapy is usually given as an oral medication during this time period.
Planning for Surgery
If adjuvant therapy is not required, then surgery may be planned at any time. For patients who have received radiation and chemotherapy, then surgery is delayed for about 6 weeks for optimal conditions. Patients are required to have a pre-operative clearance for surgery that may include labs, CXR, EKG, stress tests or pulmonary function tests. Smokers are urged to cut back or stop smoking. You will be given oral antibiotics the night before surgery, and may have to complete a bowel preparation.
Types of Rectal Cancer Surgery & What to Expect after Surgery
There are several surgical options for addressing rectal cancer. Surgeons choose the best option based primarily on removing the cancer completely. Great attention is focused on anal preservation whenever possible but education about options and outcomes is of paramount importance.
Low Anterior Resection. This is when the tumor is located in the proximal rectum, the furthest away from the anal canal. In this situation, the tumor can be removed and the upstream colon attached to the remaining rectum providing bowel continuity.
Ultra Low Anterior Resection. This is when the tumor is located in the middle area of the rectum and the majority of the rectum is removed along with the tumor. The upstream colon is then attached to the rectal stump proving bowel continuity.
Low Anterior Resection with Diverting Loop Ileostomy. This is when the resection is accompanied by also creating a temporary loop ileostomy in the right upper abdomen. This diverts stool away from the newly formed anastomosis allowing it to heal, and potentially offering protection against small leaks during the healing process. Diverting ileostomies are often used when there has been radiation damage to the rectal stump, and healing may be challenged. Sometimes the decision to use a diverting ileostomy is made during the procedure, as radiation effects cannot be assessed well pre-operatively. If a diverting ileostomy is created, then a second surgery is required to take it down and restore bowel continuity.
Abdominal Perineal Resection. This is when the entire rectum and anus are removed together and the anal opening is closed. A permanent colostomy is created with the proximal end of the descending colon. This surgery is utilized for low rectal cancers; or when one surgery would be optimal based on patient characteristics.
It is very important to sit down with your physician and discuss factors that predict the best outcomes. If fecal incontinence is present after radiation therapy, chronic diarrhea and loss of control is a real possibility. In these cases an abdominal perineal resection may be the best choice. Advanced age and other medical co-morbidities may also be important, as one surgery is easier to recover from than two.