Calcium/Vitamin D, Biomarkers & Colon Polyp Prevention (PPS4B)

• Biomarkers of Risk for Colorectal Neoplasms [ Time Frame: 1 year and 3 or 5 years ] [ Designated as safety issue: No ]
  Molecular phenotyping of a panel of putative biomarkers of risk for colorectal neoplasms in the normal appearing colorectal epithelium: COX-2, APC, β-catenin, E-cadherin, MLH1, telomerase, bcl-2, bax, TGFα, TGFβ1
  
  

Problem of Interest Colon cancer is the second most common cause of cancer death in the United States, and is the only major cancer to affect both men and women equally. There is evidence that higher amounts of calcium and vitamin D in the diet may protect against getting colon cancer, but this has not been tested in human trials until now. Much of the advance in reducing mortality from heart disease in this country has been related to making biological measurements (or "biomarkers of risk") on people, such as blood cholesterols. Such measurements help tell us who is at risk, what they need to do about it, and whether or not their efforts (diet, lifestyle modification, medications, etc) are being successful. To date, there have been no such measurements to help cancer prevention efforts. We have developed a set of biomarkers of risk for colon cancer, and in this study we will test 1) whether or not calcium and/or vitamin D supplementation can favorably affect these biomarkers in persons who are at higher than average risk for colon cancer (ie, have already undergone the removal of colon growths, called adenomatous polyps, which are known to be precursors to developing colon cancer), and 2) whether effects on the biomarkers predict who will get new colon polyps or not.

How the Problem Will Be Studied This study will be an add-on study ('adjunct study') to a 'clinical trial' that is currently already being conducted (the 'parent study'). A clinical trial is a type of study in which participants are randomly assigned to different active or inactive (placebo) treatments, and measurements of interest are obtained to see if the active treatment had the desired effect. Our study participants will be composed of persons who attend the Digestive Diseases Clinic, of the Emory Clinic who have had previous colon polyps as described above and are already participating in the "Vitamin D/Calcium Polyp Prevention Study", the parent study. In the parent study, a total of 1,964 people nationally are being randomly assigned to four different treatment groups: 1) calcium supplements, 600 mg twice a day; 2) vitamin D supplements, 500 IU twice a day; 3) both the calcium and vitamin D supplements twice a day; and 4) placebo tablets twice a day. These amounts are in the upper range of normal dietary intakes of these nutrients. Neither the participants nor the investigators, except for an emergency, know what treatment anyone is on until the study is over. The treatment period lasts three to five years at the end of which study participants undergo a follow-up colonoscopy to look for new polyps. The parent study has been underway for about a year, and there are already some patients in the trial who are receiving their study 'treatments' (ie, have been 'randomized'), but more patients will be recruited into the parent study over the next two years.

Depending on whether someone has already been randomized, they will be invited to participate in the adjunct study in one of two ways ('Aim 1' only, or 'All Aims'). First, patients (approximately 124 at Emory) who have already been randomized will be asked to allow biopsies to be made of their rectal tissue during their 3- or 5-year follow-up colonoscopy (Aim 1). Biopsies, which will be used for our biomarker measurements, are very tiny pieces of tissue that can be examined under the microscope. Second, patients (approximately 100 at Emory) who have not yet been randomized will be invited to participate more fully (All Aims) in the adjunct study. This involves having outpatient rectal biopsies taken immediately after their first phone call, their 1-year follow-up visit, and 7 - 21 days before their 3- or 5-year follow-up colonoscopy. These biopsies involve inserting a tube—about as long and big around as a doctor's examining finger—through the anus into the rectum or lower colon to a depth of about 3-4 inches. At this spot, 4 - 6 tiny pinches of tissue one mm thick (less than 1/16 of an inch) will be taken. The procedure takes less than two minutes, is painless (the only discomfort is like that of having a rectal exam), and is very low risk—about like having blood drawn. Finally, during their 3- or 5-year colonoscopy, biopsies will be taken from three areas of the colon: the rectum (same area as the outpatient biopsies), the sigmoid colon, and the ascending colon. From all of the biopsies taken from all of the visits and colon sites, biomarker measurements will be of normal proteins that occur in the surface cells lining the colon. We will then analyze whether calcium and/or vitamin D affect these biomarkers and whether the effects predict who gets new polyps.

How the Research Will Advance Scientific Knowledge and/or Human Health Colon cancer is a very common cancer and there are many factors that play a role in it. By studying the changes in the lining of the colon, we may be able to select the tests that give the most information about someone's risk for re-growing colon polyps or developing colon cancer. In the future, these tests may be used in the general population to identify individuals at high risk of developing colon cancer, determine what preventive actions need to be taken, and monitor whether the preventive actions are working well enough, just as we do for blood cholesterols in efforts to prevent heart attacks.

Also, if we find that calcium or vitamin D, alone or in combination, can favorably affect these changes in the lining of the colon, it may mean that people will have a simple and safe way to reduce their chances for re-growing colon polyps or developing colon cancer.