April 10, 2025
4 min read
Key takeaways:
- Survivors of obesity-related cancers had lower risk for death if they adhered to American Cancer Society guidelines.
- Maintaining healthy habits before and after diagnosis improved survival, too.
Nonsmokers diagnosed with obesity-related cancers had lower risk for death if they adhered to American Cancer Society nutrition and physical activity guideline for cancer survivors, according to results of a prospective cohort study.
Survivors who had the highest adherence scores related to BMI, physical activity, diet and alcohol use had a 24% reduced risk for all-cause mortality compared with those with the lowest scores.
Avoiding obesity and higher physical activity individually correlated with reduced risk for all-cause and cardiovascular disease mortality compared with the lowest scores.
“Once they are diagnosed, people will search for evidence [to reduce their risk for death],” Ying Wang, PhD, senior principal scientist in epidemiology research at American Cancer Society (ACS), told Healio. “This paper is critical for them to understand the benefits they could get from modifying their behaviors after diagnosis.”
‘Teaching moment in life’
Obesity elevates risk for 13 cancer types, according to International Agency for Research on Cancer.
Healio has previously reported results from multiple studies that examined obesity’s impact on cancer incidence and outcomes.
One showed children and adolescents with obesity at cancer diagnosis had a 29% increased risk for 5-year mortality than those without obesity.
Another showed women with early-stage breast cancer and increased BMI had a higher risk for disease-specific mortality and distant recurrence.
Increased rates of overweight/obesity have caused prevalence of early-onset colorectal cancer to rise an estimated 28% to 30%.
And individuals with obesity at first cancer diagnosis had a 29% higher risk for developing a second malignancy.
Results of studies such as these prompted ACS to update its guidelines to highlight the importance of avoiding obesity, engaging in regular physical activity and following a healthy diet.
“A cancer diagnosis is a teaching moment in life, which often motivates people to consider lifestyle changes that may help them live longer and improve their overall well-being,” Wang said.
Wang and colleagues evaluated whether these changes improved survival.
They used the Cancer Prevention Study-II Nutrition Cohort to identify nonsmokers who had been diagnosed with obesity-related cancers between 1992 and 2002. Follow-up continued through 2020.
“In the U.S., 80% of cancer survivors are never or former smokers,” Wang said. “They quit smoking most of the time after cancer diagnosis. It’s really important to understand other lifestyle factors besides smoking.”
The study population included 3,472 survivors (mean age, 67.6 years; standard deviation, 6.4 years; 80.9% women; 97.7% white).
The researchers used ACS guidelines on BMI, diet, physical activity and alcohol consumption to develop an adherence score of 0 to 8. They calculated these scores from surveys returned at least 1 year after diagnosis.
All-cause mortality served as the primary endpoint. Secondary outcomes included cardiovascular disease mortality and cancer-specific mortality.
‘It’s not too late’
In all, 64.9% of the study population died during median follow-up of 15.6 years (interquartile range, 8.4-18.3).
Individuals who had high ACS guideline scores (6 to 8) had significantly lower risk for all-cause mortality (HR = 0.76; 95% CI, 0.68-0.85), cardiovascular disease mortality (HR = 0.67; 95% CI, 0.54-0.83) and cancer-specific mortality (HR = 0.79; 95% CI, 0.64-0.97) compared with those with low scores (0 to 3).
Survivors who had an optimal BMI score (2) — meaning non-obese — had decreased risk for all-cause mortality (HR = 0.9; 95% CI, 0.81-0.99) and cardiovascular disease mortality (HR = 0.73; 95% CI, 0.6-0.88) compared with individuals who had a BMI score of 0.
Those who had a peak physical activity score (2) also had reduced risk for all-cause mortality (HR = 0.78; 95% CI, 0.71-0.87) and cardiovascular disease mortality (HR = 0.74; 95% CI, 0.61-0.9) compared with those who had a score of 0.
However, individuals who had a higher alcohol score (2), meaning they did not consume it, had increased risk for all-cause mortality (HR = 1.2; 95% CI, 1.04-1.39) compared with those with the lowest score (0). Researchers did not observe elevated risk for cardiovascular disease mortality or cancer-specific mortality based on higher alcohol score.
Survivors who had an ACS score of at least 5 before and after their diagnosis had decreased risk for all-cause mortality (HR = 0.79; 95% CI, 0.71-0.88), cardiovascular disease mortality (HR = 0.69; 95% CI, 0.57-0.85) and cancer-specific mortality (HR = 0.83; 95% CI, 0.68-1.02) compared with individuals who maintained scores of 4 or below.
Those who increased their score from 0 to 4 before diagnosis to at least 5 after diagnosis had lower risk for cardiovascular disease mortality (HR = 0.74; 95% CI, 0.56-0.99) than those whose scores did not improve.
“It’s not too late for cancer survivors to change their lifestyle behaviors,” Wang said. “Regardless of their prediagnosis behavior, if they improved their behavior after diagnosis, we still see survival benefits.”
Researchers acknowledged study limitations, including the study’s observational nature, use of self-reported data, lack of diversity and one-time measurement of lifestyle factors after diagnosis.
Wang and colleagues are investigating how survivors’ adherence to ACS guidelines relates to mental and physical health and sleep quality.
They also are examining the potential association between ACS guideline adherence and prostate cancer incidence and mortality among men without cancer.
“In the future, I can imagine using biomarkers,” Wang said. “We want to better understand the mechanisms underlying those associations [and] what metabolic pathways those modifiable lifestyle factors impact.”
For more information:
Ying Wang, PhD, can be reached at ying.wang@cancer.org.
Sources/Disclosures
Disclosures:
The authors report no relevant financial disclosures.