THE SCOPE OF NUTRITION INTERVENTION TRIALS WITH CANCER-RELATED END-POINTS

The National Cancer Institute currently is supporting three full-scale dietary modification trials with cancer-related endpoints. These stud ies are the dietary component of the Women's Health Initiative, design ed to determine whether a low-fat diet will reduce the incidence of br east and colorectal cancer and/or coronary heart disease; the Women's Intervention Nutrition Study, designed to test whether a dietary fat r eduction program will decrease breast cancer recurrence and increase p atient survival; and the Polyp Prevention Trial, designed to determine whether a low-fat, high-fiber diet will reduce the recurrence of aden omatous polyps. Design issues associated with these full-scale dietary modification outcome trials have been addressed successfully in a ser ies of feasibility studies. The ability to achieve a sustained reducti on of 50% in dietary fat intake with maintenance of nutritional adequa cy has been demonstrated in randomized trials of postmenopausal popula tions with resected breast cancer and in populations at increased risk for breast cancer. In these studies comparing dietary fat reduction p rograms with control lifestyles, a series of associated biologic chang es, consistent with the self-reported dietary alterations, have been o bserved. These changes include body weight reduction, serum and/or pla sma estradiol concentration reduction, fasting plasma cholesterol conc entration reduction, and alteration in free fatty acid levels. Such re sults provide a substantial basis for reliably estimating the level of adherence that can be anticipated in trials of dietary change, a prer equisite for appropriate calculation of the sample size needed for mul ticenter, full-scale outcome studies. As a result, the efficacy of a s eries of dietary alterations (including fat reduction, fiber addition, and/or increased fruit and vegetable intake) on cancer-related endpoi nts with potential major public health significance (breast cancer rec urrence, breast cancer development, and colonic polyp recurrence) now are being addressed definitively in prospective clinical trials.