Can lifestyle factors affect mortality outcomes in colorectal cancer?

This study evaluated the association between lifestyle factors and mortality in colorectal cancer.

To date, few studies have examined the relationship of lifestyle factors with mortality among patients with colorectal cancer. The American Cancer Society Guidelines on Nutrition and Physical Activity for Cancer Survivors highlight that survivors should achieve and maintain a healthy weight throughout life, be physically active and eat a healthy diet with an emphasis on plant foods. Other cancer research groups also suggest limiting alcohol consumption.

As cancer survivors are at increased risk of second cancers and comorbidities (co-existing diseases), following an overall healthy lifestyle pattern may be important for improving overall survival. This study analyzed the relationship between pre-diagnosis lifestyle factors and 5-year all-cause mortality (death for any reason), colorectal cancer-specific mortality (death from colorectal cancer) and cardiovascular mortality (death from coronary artery disease, stroke or heart attack).

This study evaluated the records of 4,213 colon cancer cases and 1,514 rectal cancer cases. During the 5-year follow-up, 1,273 of the colon cancer patients died. 856 deaths were due to colon cancer, 125 were due to other cancers, 108 were due to cardiovascular disease and 184 were due to other causes. During the 5-year follow-up, 454 of the rectal cancer patients died. 301 deaths were due to rectal cancer, 49 were due to other cancers, 43 were due to cardiovascular disease and 61 were due to other causes.

In colon cancer pre-diagnosis smoking was associated with an increased risk of 5-year all-cause mortality. Compared to never-smokers, those who were current smokers had a 74% increased risk of death from any cause over the 5 years and a 46% increased risk of death from colorectal cancer. For patients who had already quit cigarettes, there was only a 1% increased risk of death from colorectal cancer compared to those who had never smoked.

Body mass index (BMI) is a measurement of whether someone is over-or underweight, calculated by dividing their weight in kilograms by the square of their height in meters.  In general, a patient with a BMI of over 30 kg/m² is considered obese. In colon cancer, compared to normal-weight individuals (BMI of 18.5 – 24.9 kg/m²), those who were obese had a 19% increased risk of death from any cause, and an 84% increased risk of death from cardiovascular disease. There was a trend towards a 15% increase in risk of colorectal cancer-specific death for obese patients, but this failed to achieve statistical significance.

In rectal cancer cases, those who were current smokers had 2.63 times the risk of death from cardiovascular disease compared to never-smokers.

The Healthy Eating Index-2005 is a measure of diet quality that assesses conformance to Federal dietary guidance. It assesses intake of fruit (whole and juice), vegetables (in particular dark green and orange vegetables and legumes), total grains, whole grains, milk, meat and beans, oils, saturated fat and sodium.  In rectal cancer, those with the highest index scores (77 – 90.2; indicating conformance to federal dietary guidelines) had a 40% reduction in the risk of all-cause mortality compared to those with the lowest scores (21.8 – 56.7; indicating non-conformance or low conformance to guidelines). Those with the highest index scores had a 36% reduction in risk of colorectal cancer-specific mortality compared to those with the lowest scores.

Lifestyle scores took into account the patients’ Healthy Eating Index-2005 scores, BMI measurements, physical activity, alcohol intake and smoking habits. Participant received one point for meeting each of the following recommendations: BMI from 18.5 – 25 kg/m², at least 3 episodes of physical activity per week, Healthy Eating Index-2005 scores of above 71.5, one or fewer drinks per day for women, 2 drinks per day for men and not smoking. For colon cancer cases, compared to those with a score of 1 or less, those who met all 5 recommendations (a score of 5) had a 34% reduced risk of death. For rectal cancer cases, compared to those with a score of 1 or less, those who met all 5 recommendations had a 46% reduced risk of death.

In summary, the authors found that healthier lifestyle before colorectal cancer diagnosis was associated with improved overall survival after diagnosis with colorectal cancer. This information is also useful when considering the risk of recurrent cancer.

Lifestyle factors data was only collected once, before diagnosis and therefore the study does not take into account how diagnosis of cancer may affect these factors.