COLORECTAL CANCERS

    Although colon and rectal malignancies are the second most common cancer in the U.S., little attention was given to it especially when screening can effectively reduce the incidence and death rate. When Katie Curic advocated for screening colonoscopy, a significant increase in numbers of Americans undergoing such procedure took place. Indeed the majority of colorectal carcinoma develop from a growth starting as a bump on the surface of the bowel and growing to an inch or larger.  This process usually takes several years and the responsible polyp can be detected by colonoscopy and X-rays with contrast.  When snipped off before it becomes cancerous, subsequent morbidity associated with colorectal cancer is prevented. It is a disease of developed countries where the incidence can be several fold higher than in individuals leading the hunter/gatherer life style.  When symptoms develop, such as rectal bleeding, change in bowel habits or weakness due to anemia, the diagnosis can be confirmed by endoscopy and biopsy, and it usually grown already into an advanced stage.  Screening, early detection and prevention is by far preferable to finding the established cancer.

 

MINIMALLY INVASIVE RESECTION

   Clearly, in some patients, minimally invasive techniques can lead to more rapid healing, and lesser pain in the post-operative period. The techniques are still in evolution. The tumor can be removed through a smaller incision combining the use of the surgical hand, intra-abdominal camera view magnification, and laparoscopic instruments. Or the technique can begin with laparoscopic surgery, then the tumor can be delivered and bowel re-connection performed outside the abdomen by making a small incision.    From a cancer control standpoint we cannot yet endorse using laparoscopic techniques for T3 and T4 tumors due to the potential for tumor cell spillage and higher rates for local and regional recurrence.

   It is easy to be persuaded by someone who shows the result of small scars and swift recovery and conclude that minimally invasive surgery is superior to other operations requiring a larger incision. The result that really counts is the cure and disease free rates and admittedly these results are harder to measure and not available at this time.  The best option is to consult a seasoned surgical oncologist who has a track record in obtaining high cure rates and who can also employ the techniques of minimally invasive surgery. One must also consider the options of chemo and biological therapy with or without radiation to minimize the risk of recurrent disease.

  Much publicity has been given to the robotic techniques.  The Da Vinci robot (Intuitive Surgical, Inc) has the advantage of reproducing the surgical wrist motion and has slightly increased visual depth due to the bicameral optics, however it lacks in the touch sensory ability of the hand held laparoscopic instruments, it has long set up time, higher cost and need for greater personnel assistance.  It has created a cadre of prostate and heart surgeons who prefer the robot.  In colorectal surgery, ho wever,the advantages have yet to be demonstrated.

 

HOW TO AVOID A COLOSTOMY

  The surgical goals in colorectal cancer is to remove the tumor with surrounding tumor drainage in lymph nodes to assure low local, regional and distant recurrences. In order to accomplish this goal, sufficient margin on the bowel itself and on the mesentery (vascular and lymphatic network of the bowel) need to be removed. Re-connection or anastomosis of the bowel can be done with staples or suturing techniques. When it is not safe or technically impossible, then a colostomy (most likely temporary) is placed to the abdominal skin. For non-rectal cancers, the colostomy is usually temporary, and re-connection can be performed as early as two months.  Some rectal cancers require a permanent colostomy depending on the stage and proximity to the anus.  The risk of avoiding a permanent colostomy for cancers near the anus needs to be balanced by the risks of  cancer recurrance.  This risk can be reduced with pre-operative chemoradiation and newer surgical techniques which preserves the anus and resects the tumor clear of the anal structures.

PREVENTION AND COLONOSCOPY

   It is intuitive that eating "healthy" diet will protect you against colorectal cancers.  Proving this common "observation" has been difficult and no specific reccomendations can be rendered. General advice for the healthy diet is high in fruits and vegetables, low in animal protein and fat and moderate calories.  Animal studies have indicated that balanced diet resulting in reduction of 10-15% below the ideal weight decreases cancer risk and increases longevity.  Exercise and physical activity is also associated with reduction of cancer risk. The risk is not limited to colon cancers and also contribute in reduction of cardiovascular diseases.

   Studies in patients with the precursor of colon cancer, the polyp, have indicated the value of aspirin, calcium and selenium. At this point in time, a baby aspirin daily can decrease the risk of recurrent polyps and probably of cancer as well.  This risk reduction could be offset by the risk of stomach irritation and bleeding.  More studies are required to refine the risk reduction in groups with increased risk of polyps and cancer compared to potential risks of side effects of the treatment.

  Colonoscopy is the most effective way to screen for colon and rectal cancers.  Low risk individuals should begin with their first colonoscopy at 50 years of age and every 10 years if low risk is established.  The screening should be more frequent and start at younger age, if there is a family history of cancer or if polyps are found.

    The Southwest Oncology Group will soon be sponsoring a prevention trial, the CASE STUDY which will enroll patients with known polyps, recently treated early colorectal cancers and patients who are survivors of colorectal cancers. This trial will randomize volunteers on baby aspirin to the combination of aspirin, calcium and selenium.

NEW STUDY FROM THE WOMEN'S HEALTH INITIATIVE (WHI):

    Vitamin D 400 IU per day and Calcium 1000 mg daily was not associated with decrease colorectal cancer rates (New England Journal of Medicine, March 2006, volume 354, pages 7-14).  Calcium at 1500 mg daily has been found to lower recurrent polyp rates in a population with known adenomas that were cleared with colonoscopy (Baron et al. New England Journal of Medicine, 1999) and in a trial employing recently resected colorectal cancer patients using 1800 mg of calcium on a daily basis (Chu et al, abstract AACR Prevention Research 2007).  The possible discrepancy can be explained by the lower calcium dose in the WHI study and the fact that the women on study did not undergo systematic colonoscopies at the beginning and end of study which spanned over 5 years.  The lesson of WHI study is that for effective prevention,  screening must be carried out even when effective chemopreventive agents are taken.