Insulinogenic diet linked to worse colon cancer survival

Last Updated: 2018-07-03

By Anne Harding

NEW YORK (Reuters Health) - Patients with stage III colon cancer who consume a more insulinogenic diet have higher rates of cancer recurrence and death, according to new findings published in the Journal of the National Cancer Institute.

"This study is important because it is another piece of evidence in an increasing literature suggesting that modifiable diet and lifestyle behaviors may actually play a very important role in risk of cancer recurrence," Dr. Kimmie Ng, director of clinical research at Dana-Farber Cancer Institute in Boston and the study's senior author, told Reuters Health in a telephone interview.

While the American Cancer Society (ACS) has released diet and lifestyle recommendations for cancer survivors, Dr. Ng noted, the advice these patients actually receive is "very variable."

In a separate paper published online April 12 in JAMA Oncology, Dr. Ng and her colleagues reported that stage III colon cancer patients whose diet hewed closest to the ACS recommendations had a 42% lower risk of dying during the study period, and improved disease-free survival (DFS). (http://bit.ly/2MIzt76)

In the new study, Dr. Ng and her team looked at food insulin index (FII), a measure that accounts for the insulinogenic effects of proteins and fat as well as carbohydrates. Dietary glycemic load only addresses carbs.

They analyzed data from the CALGB 89803 trial of adjuvant chemotherapy in 1,023 patients with resected stage III colon cancer, who reported their dietary intake during chemo and six months after the end of treatment. The researchers used FII to calculate dietary insulin load and dietary insulin index.

Patients in the top quintile for dietary insulin load had worse DFS than those in the bottom quintile (adjusted hazard ratio 2.77), while dietary insulin index was also associated with worse DFS (aHR 1.75). Higher dietary insulin load had the strongest relationship with worse DFS in obese individuals (HR 3.66). However, mutations of KRAS, BRAF, PIK3CA, TP53 and microsatellite instability did not affect the association.

Following a more Mediterranean or "prudent" diet, compared to a Western diet pattern, will lead to a lower insulin response, Dr. Ng said. "We have to be cautious in focusing on any one particular type of food. All of these things act together when they're ingredients as part of a meal."

Discussing diet and physical activity with cancer survivors can be empowering, Dr. Ng said, because they often feel as if they have no control over their disease. "I'm not sure that it's being uniformly discussed with cancer survivors, and it would be important to do so," she added.

Dr. Peter Campbell, scientific director of epidemiology research at the American Cancer Society in Atlanta, reviewed the study for Reuters Health. He noted that translating dietary scores into dietary recommendations "isn't easily done," that the study was not a clinical trial, and that the authors did not include blood biomarkers to back up the findings.

Nevertheless, he added, "it's a really well conducted study. It's added a lot to the literature on colon cancer recommendations for patients, and I look forward to seeing more out of this group on these topics and seeing if we can replicate this work in our own cancer prevention study."

SOURCE: http://bit.ly/2MLpUEi

J Natl Cancer Inst 2018.