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Diet may affect colon cancer outcomes
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A diet with a high insulin load increased risk for colon can recurrence and mortality, according to results of a prospective, observational study.
Thus, dietary factors may play a role in colon cancer recurrence and survival following resection.
“We now have evidence that [patients] may help avoid a recurrence of the disease and improve their prospects of survival by following a healthy diet,” Vicente Morales-Oyarvide, MD, MPH, from the department of medicine at DanaFarber Cancer Institute, said in a press release. “These research results should be empowering to this group of patients.”
Previous studies have shown that colon cancer survivors who have a healthy lifestyle have better prognosis than survivors who harbor less healthy lifestyles.
Epidemiological research has suggested insulin may play a role due to its signaling abilities relevant to colon cancer pathogenesis and response to treatment.
Morales-Oyarvide and colleagues evaluated the association of dietary insulin load and dietary insulin index with disease recurrence and survival for patients with resected stage III colon cancer.
Investigators also assessed whether microsatellite instability (MSI) and mutational status of KRAS, BRAF, PIK3CA and TP53 affected the association between dietary insulin scores and patient outcomes.
Researchers evaluated dietary questionnaires from 1,023 patients enrolled in the Cancer and Leukemia Group B (CALGB) phase 3 trial for patients with stage III colon cancer, which compared adjuvant chemotherapy with weekly 5-FU and leucovorin vs. weekly irinotecan, 5-FU and leucovorin.
Patients completed questionnaires focused on dietary and lifestyle habits 4 months after surgery and 6 months after completion of adjuvant therapy. The validated questionnaires included 131 food items, as well as questions on vitamin and mineral supplements. Patients also reported average frequency with which they consumed a specific food portion size over the previous 3 months.
Researchers estimated nutrient intake by multiplying the regularity of consumption of each food by the nutrient content of the specified portions using composition values from Department of Agriculture sources supplemented with additional data.
Researchers calculated the dietary insulin load — or the level of insulin produced by the body in response to diet — for each patient by multiplying food insulin index with kilocalories per serving and amount of servings per day. Researchers used this measurement — which they multiplied by 100 and divided by total daily energy intake in kilocalories — to calculate the dietary insulin index.
Diets high in simple carbohydrates, sugar and fat — common features of Western diets — are associated with higher insulin levels, whereas Mediterraneanstyle diets rich in vegetables, fruits, legumes, and healthy fats and proteins are associated with lower insulin levels.
Overall dietary insulin load is informative because it accounts not only for carbohydrate consumption, but fat and protein consumption as well, MoralesOyarvide said.
DFS — defined as time from completion of first questionnaire to colon cancer recurrence, occurrence of new primary colon cancer or mortality related to any cause — served as the study’s primary endpoint.
Other study endpoints included RFS and OS.
Total follow-up was 7 years; follow-up occurred every 3 to 4 months for the first 4 years, then annually for 3 years. Tasks performed at follow-up included serum carcinoembryonic antigen, chest X-rays and CT scans.
For dietary insulin scores, 204 patients scored in quintiles 1 and 5, whereas 205 patients scored in quintiles 2, 3 and 4.
Analyses showed high dietary insulin load was significantly associated with worse DFS (adjusted HR for highest vs. lowest quintiles = 2.77; 95% CI, 1.9-4.02). The association between dietary insulin load and patient outcomes occurred independently of Western and prudent diets, the researchers found.
A high dietary insulin index also appeared associated with worse DFS (HR for highest vs. lowest quintile = 1.75; 95% CI, 1.22-2.51).
RFS and OS results were similar to those for DFS.
The association between higher dietary insulin load and worse DFS varied based on BMI; patients with obesity appeared to have exhibited the strongest association (HR = 3.66; 95% CI, 1.88-7.12).
“Overweight and obese patients in our series might have had elevated basal levels of circulating insulin that were further increased by high dietary insulin load, resulting in higher plasma insulin than a lean patient following the same diet,” the researchers wrote.
Dietary insulin load influence on cancer outcomes did not differ according to mutation status of KRAS, BRAF, PIK3CA or TP53, or with MSI.
“Patients are always interested in what they can do to reduce their risk of cancer recurrence,” Kimmie Ng, MD, MPH, director of clinical research in the gastrointestinal cancer center at Dana-Farber Cancer Institute, and lead study author, said in a press release. “We now have dietary advice that, our research shows, may make a difference.” – by Melinda Stevens
Disclosure s : The authors report no relevant financial disclosures.
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