The rectum and colon forms the distal most part of the digestive system, and cancers of the colon and rectum are often grouped together under the term colorectal cancer. The rectum (last 12 – 15cm of the colon) is however distinctly different in terms of anatomy and function from the rest of the colon and is therefore treated separately and differently from other colon cancers. The rectum is also confined to the bony pelvis. This makes it ideal for administering radiotherapy as it is in a fixed position, and there are no other sensitive organs close by that will be damaged by the radiotherapy.
What are the symptoms of rectum cancer?
Signs and symptoms of rectum cancer include:
Patients with rectal cancer will mostly present with symptoms of passing fresh blood per rectum (which might be falsely attributed to piles and lead to a delay in diagnosis) and tenesmus (the feeling that something remains in the rectum after passing a stool).
Once the diagnosis has been confirmed with a colonoscopy and biopsies of the tumour, the patient will be staged by performing a CT scan of the chest and abdomen and an MRI scan of the pelvis and/or an endo-anal ultrasound.
The MRI scan will provide valuable information on the position, size and extent of rectal cancer. Most rectal cancers (except the very early ones) will now be treated with pre-operative (also called neo-adjuvant) radiotherapy. A mild dose of chemotherapy will be added to improve the effectiveness of the radiotherapy. This usually takes 2 - 3 months to complete.
What are the possible treatment options for rectal cancer?
Once the neo-adjuvant treatment is completed, the patient will be re-evaluated for surgery:
For very early tumours it might be possible to perform a transrectal endoscopic microsurgical (TEM) resection of the cancer, thus avoiding major abdominal surgery.
The close proximity of the anal sphincters (muscles that ensures continence) makes surgery of the rectum difficult. If the cancer is very close to these muscles, they have to be resected, and the patient will be left with a permanent stoma/colostomy. By administering radiotherapy pre-operatively, the cancer can be reduced in size, which theoretically might make it possible to save these important muscles.
For all other tumours, the position of the cancer relative to the anal sphincters will determine what procedure will be done. Whatever procedure is done, the resection of the rectum needs to be done employing the technique of total mesorectal excision (TME). With this technique the whole rectum as well as all the lymphatic tissue that drains it is resected as an intact ‘package’. The introduction of this technique is partly responsible for the recent reduction in local recurrence rates seen after rectal resections.
If the cancer is far enough away from the sphincters, the patient will undergo a low anterior resection (LAR). During this procedure, Dr Cooper will resect the rectum and the upper (proximal) colon is brought down and joined (anastomosed) to the remaining rectum. This anastomosis has a high leak rate with potentially serious complications. In order to avoid these complications, the surgeon may recommend an ileostomy (bringing the distal small bowel out as a stoma) which will be performed as a temporary measure. This stoma will divert stool from the anastomosis and will give it time to heal. It will be reversed in 6 – 12 week’s time. This procedure (LAR) can be done in an open or minimally invasive manner.
If the sphincters cannot be saved, the patient will undergo an abdominoperineal resection (APR). During this procedure Dr Cooper will resect the rectum as well as the sphincters. The perineum (bottom) is sutured close, and the upper (proximal) colon is brought out onto the skin as a permanent colostomy/stoma. This procedure (APR) can be done in an open or minimally invasive manner.
Adjuvant (post-operative) treatment will be necessary in most cases. The need for this will be determined by the pathological (histological) features of the cancer. It may consist of conventional chemotherapy and/or targeted/immunological therapy.