Good diet and exercise habits may improve survival rates for people who have colon cancer, according to results of an observational study published April 12 in JAMA Oncology.
Patients with stage III colon cancer and a lifestyle considered highly consistent with the American Cancer Society (ACS) guidelines on diet and exercise had a 42% lower relative risk for death compared with patients who did not, said Erin L. Van Blarigan, ScD, from the University of California, San Francisco, and colleagues.
In an accompanying editorial, Michael J Fisch, MD, MPH, and coauthors urged physicians to heed the lesson about the applicability of the ACS Nutrition and Physical Activity Guidelines for people already facing colon cancer.
"If you were skeptical about emphasizing nutrition and physical activity for colorectal cancer survivors based on the nature of the end points previously examined or the size of demonstrated effects, or the fact that most of the similar studies were conducted among patients with breast cancer, these data should soften those concerns," write Fisch, who works for Anthem's AIM Specialty Health, Chicago, Illinois, and coauthors.
The editorialists also say that the new study will allow physicians who previously gave vague advice about diet and exercise to be more precise, and recommend five to six servings of fruits and vegetables per day and 150 minutes of exercise per week.
The editorialists describe the findings as a "cancer control gem that came out of the ashes of" an earlier failed trial.
That trial was the Cancer and Leukemia Group B (CALGB) 89803 study, a chemotherapy trial among patients with colon cancer involving irinotecan and started about 20 years ago. However, a lifestyle survey was administered in the clinic during and after chemotherapy as part of this study. After exclusions, there were 992 patients eligible for analysis by Van Blarigan and colleagues for an observational study.
Over a 7-year median follow-up, there were 335 recurrences and 299 deaths, including 43 deaths without recurrence. Compared with patients with a poor ACS guidelines score (0 to 1; n = 262; 26%), patients with an excellent score (5 to 6; n = 91; 9%) had a 42% lower relative risk for death during the study period (hazard ratio [HR], 0.58; P = .01 for trend) and improved disease-free survival (HR, 0.69; P = .03 for trend).
High adherence to the ACS guidelines (score of 5 to 6) was also associated with a 9.0% absolute reduction in the risk for death at 5 years compared with a score of 0 to 4, reported the study authors.
The editorialists described that mortality difference as "striking."
There may be no harm in recommending that patients who have stage III colon cancer adopt the ACS lifestyle recommendations, while acknowledging that this may be difficult for them, Van Blarigan said in an JAMA podcast interview.
"There's no reason to put it off, but they may not feel up to it if they are currently undergoing treatment," she said.
There's a demand for this kind of detailed information about lifestyle recommendations for people who have been treated for colon cancer, said senior study author, Jeffrey A. Meyerhardt, MD, MPH, from the Dana-Farber Cancer Institute in Boston, Massachusetts, in the same podcast.
"That's a question that patients ask a lot about…'What should I eat? Should I exercise?'" he said.
More Study Details
To compare outcomes based on lifestyle choices, the study authors assigned an ACS guidelines score for each included patient based on a combination of factors: body mass index; physical activity; and intake of vegetables, fruits, whole grains, and red and processed meats. As noted above, scores ranged from 0 to 6, with higher numbers indicating healthier behaviors.
The researchers also examined the connections between these factors and death after colon cancer on their own.
They reported that patients with a body mass index (BMI) of 25.0 to 29.9 had lower risk for death than patients with a BMI of 30 or higher. Compared with patients who abstain from alcohol, heavy drinkers had a non–statistically significant increased risk for death, while patients consuming low to moderate amounts of alcohol had a non–statistically significant decreased risk for death, the authors said.
Consuming five or more servings of vegetables and fruits per day appeared to be helpful, but the findings on red and processed meat ran contrary to what might be expected, the authors said. Low intake of red and processed meat after colon cancer was associated with an increased risk for death.
"Higher protein intake may be beneficial for cancer survivors," Van Blarigan and study colleagues write. "Thus, it is possible that red meat is inversely associated with colon cancer mortality, despite being positively associated with colon cancer incidence."
The authors noted the limitations of their study. They couldn't conclude, for example, that the associations are independent of a patient's prediagnosis lifestyle or that changing behaviors after cancer diagnosis can achieve these results. They also pointed out that the study population was predominantly white and may not be representative of all patients with colon cancer.
The National Cancer Institute funded this study. The study authors and editorialists have disclosed no relevant financial relationships.
JAMA Oncol. Published online April 12, 2018. Abstract