A major weapon against colon cancer's return could lie in the foods patients eat every day, suggests research published recently in the Journal of the American Medical Association.
A multi-center team led by Dr. Jeffrey A. Meyerhardt, of the Dana-Farber Cancer Institute, Boston, tracked the clinical outcomes of 1,009 patients with node-positive (stage III) colon cancer for a median of 5.3 years. All of the patients had received surgery and postoperative adjuvant chemotherapy as part of a National Cancer Institute-sponsored randomized trial.
However, Dr. Meyerhardt and colleagues also used a reliable, standardized food-frequency questionnaire to track each patient's post-operative intake of 131 different foods.
They looked specifically at two dietary patterns: the so-called "prudent" diet, which relies heavily on fruits, vegetables, poultry and fish; and the 'Western' diet, with its emphasis on red and processed meat, french fries, refined grains and sweets.
While stressing that an observational study cannot definitively determine a cause-and-effect relationship, the team found that "increasing consumption of a Western dietary pattern after diagnosis was associated with an increased risk of cancer recurrence or death" in this cohort of colon cancer patients.
In fact, patients who scored in the top 20 percent in terms of their adherence to the Western diet had almost three times the risk of death or cancer recurrence, compared to people at the bottom of the scale -- closer to the "prudent" diet. That trend persisted even after the team accounted for confounders, such as age, sex, body mass index, level of physical activity, type of treatment, or number of positive lymph nodes.
Why the association between diet and colon cancer recurrence? The study wasn't designed to determine which specific foods &ndash if any &ndash might be responsible. But the researchers note that prior studies have linked Western diets to increased colon cancer risk. Research has also suggested that Western dietary regimens strongly affect insulin levels.
"Both insulin and insulin-like growth factors have been associated with enhanced tumor growth" as well as the suppression of cancer-cell death (apoptosis), according to the study authors. They speculate that, following colon cancer surgery, diets heavy in fat and sugars might therefore "facilitate a milieu that allows microscopic disease to proliferate and spread."
Comment:
In the field of cancer prevention, we all have had a particular fascination with the potential role of diet as a major factor. In truth, despite extensive research, we only recognize a few pockets of where and how this major aspect of our lives plays a significant part. Intuitively, we assume that it is in the cancer of the gastrointestinal tract where diet is likely to have its largest impact, and, indeed, there are data to suggest that increased fruit and vegetable intake, decreased meat and fat intake, as well as caloric restriction all are protective for colorectal cancer.
When the colon cancer patient and spouse sit in the oncologist’s office, however, almost invariably, after reviewing the reports and discussing chemotherapy options, the question will arise, "But what should he/she eat?" Till now, the objective oncologist was usually reduced to mouthing some cliches and pieties about moderation and a good diet and enough vitamins. But here, at last, is a study that, while not at the highest level of evidence (a randomized trial), provides reasonably clear-cut data to support the oncologist in recommending the prudent diet for his patients.
For now, we must remember that it is but an observational study. Was the association truly causal or did those who ate prudently do other things that made them more likely to do well? The WINS study, a randomized trial of a low fat diet in breast cancer patients, suggested that dietary restriction could indeed improve relapse-free survival in cancer patients undergoing normative cancer therapy, so there is room for optimism that the same will be true for this finding as well.
- Alfred I. Neugut, MD, PhD, Columbia University College of Physicians and Surgeons and Mailman School of Public Health/NewYork-Presbyterian Hospital, New York City
