Oncologists whose patients with treated early colon cancer ask what they can do to prevent it from coming back can now more strongly endorse lifestyle modification, based on findings from a pair of cohort studies reported at a presscast leading up to the annual meeting of the American Society of Clinical Oncology.
Both studies were conducted among more than 800 patients with stage III colon cancer participating in a nationwide randomized adjuvant chemotherapy trial who completed comprehensive lifestyle questionnaires.
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Data for the studies were collected prospectively, noted ASCO President Daniel F. Hayes, MD. “So, that takes a lot of the biases out of the classic retrospective observational studies where patients are asked, ‘Do you remember what you did several years ago?’ Most of us would not. In this case, it was in real time, so it makes these findings even more compelling, in my opinion.
“We can now present optimism to patients with early-stage colon cancer,” Dr. Hayes added. “The odds of surviving colon cancer if it is not metastatic are quite high these days, thanks to lots of hard work and a number of trials done over the last 30 years showing that adequate surgery and adjuvant chemotherapy improve survival.”
Therefore, patients today have even more reason to make a commitment to a healthy lifestyle, which may further improve their outcomes, in addition to its other benefits, he commented.
At the same time, the studies’ findings should not be used to justify skipping good standard of care treatment for early colon cancer, stressed Dr. Hayes, who is also clinical director of the breast oncology program and Stuart B. Padnos Professor in breast cancer research at the University of Michigan in Ann Arbor.
“Nobody wants to undergo chemotherapy. We understand that,” Dr. Hayes said. “But chemotherapy clearly saves lives, so people should not interpret these two abstracts as suggesting that, if you live a healthy lifestyle and if you eat tree nuts, you don’t need to take the chemotherapy that your oncologist would recommend. That’s a very dangerous interpretation, and it’s not what we’re trying to get across. It’s that healthy people live healthier.”
In the first study, Erin Van Blarigan, ScD, assistant professor of epidemiology and biostatistics, University of California, San Francisco, and her colleagues assessed adherence to the American Cancer Society’s Nutrition and Physical Activity Guidelines for Cancer Survivors among 992 patients with stage III colon cancer who enrolled in the Cancer and Leukemia Group B (CALGB) 89803 adjuvant chemotherapy trial within 8 weeks of cancer resection.
“The guidelines are based on published scientific studies, but it’s not actually known if patients who follow the guidelines after diagnosis live longer,” she explained in the presscast.
All patients completed a validated lifestyle questionnaire during and 6 months after completing chemotherapy. Responses were used to assign patients points reflecting guideline adherence on body weight; regular physical activity; a dietary pattern high in vegetables, fruits, and whole grains, and low in red meat and processed meat; and alcohol intake (not specifically included in the guidelines but described in the text).
When lifestyle scores were calculated without consideration of alcohol intake, 26% of patients had a score of 0-1, corresponding to the least healthy lifestyle, while 9% had a score of 5-6, corresponding to the most healthy lifestyle, Dr. Van Blarigan reported.
Risks of both disease-free and overall survival events fell significantly with increasing score (P = .01). Compared with peers who scored 0-1, patients who scored 5-6 had a 42% lower risk of death.
When lifestyle scores were calculated with consideration of alcohol intake, 19% of patients had a score of 0-2, while 16% had a score of 6-8.
Here, too, risks of both disease-free and overall survival events fell significantly with increasing score (P = .002). Compared with peers who scored 0-2, patients who scored 6-8 had a 51% lower risk of death.
“Colon cancer patients who had a healthy body weight, engaged in regular physical activity of approximately 1 hour 5 days a week, and ate a diet rich in a variety of vegetables and fruit – choosing whole grains over refined ones, avoiding red and processed meats, and drinking small to moderate amounts of alcohol – had longer disease-free and overall survival, compared with patients who did not engage in these behaviors,” summarized Dr. Van Blarigan.
The mechanism by which low to moderate alcohol intake, compared with none, may be protective is unclear, but the pattern is consistent with that seen for other diseases, she said.
“There has been some literature in cardiovascular disease about changes in insulin and inflammation and elasticity of blood vessels and things like that,” Dr. Van Blarigan noted. “So, I think that’s something to explore further for colon cancer.”
In the second study, Temidayo Fadelu, MD, a clinical fellow in medicine at the Dana-Farber Cancer Institute in Boston, and his colleagues assessed nut intake among 826 patients enrolled in the same trial. They used questionnaires completed 6 months after the end of chemotherapy, which asked about consumption of tree nuts, peanuts, and peanut butter.
“States of energy excess are associated with an increased risk of colon cancer death and recurrence … and one mechanism is thought to maybe be hyperinsulinemia,” he commented in the presscast. Research has found nut consumption to be associated with lower incidences of type 2 diabetes, metabolic syndrome, and insulin resistance.
Study results showed that the adjusted risks of both disease-free survival and overall survival events fell with increasing frequency of total nut consumption. Patients eating nuts at least twice weekly (19% of the cohort) had a 42% lower adjusted risk of disease-free survival events and a 57% lower adjusted risk of death, relative to counterparts who never ate nuts.
“We don’t really know what the underlying biologic mechanism is for this association, but we hypothesize that it’s perhaps due to the influence of nuts on insulin resistance,” Dr. Fadelu said, noting that they contain fatty acids, fiber, and flavonoids and that insulin levels rise to a lesser degree after eating nuts than after eating foods such as simple sugars. “There need to be further studies to really evaluate this hypothesis,” he added.
“We did a secondary analysis, and we observed that the association described was limited to tree nuts; the association was not seen with peanuts or peanut butter intake,” noted Dr. Fadelu, who reported that he had no disclosures. “Peanuts are technically legumes, and this difference may perhaps be due to the different biochemical composition between peanuts and tree nuts.”
Dr. Van Blarigan reported that she had no disclosures. Dr. Fadelu reported that he had no disclosures.