Prognostic factors in early breast cancer associated with body mass index, physical functioning, physical activity, and comorbidity: data from a nationwide Danish cohort

Purpose: To explore the associations between lifestyle-related factors and tumor-related prognostic factors in women treated for primary breast cancer, and to detect possible differences between the associations in pre- and postmenopausal women.

Methods: Associations between tumor-related prognostic factors, including the composite endpoint risk of recurrence (RoR), body mass index (BMI), comorbidity (Charlson comorbidity index), basic physical functioning (SF-36), physical activity, smoking, and alcohol consumption were examined with binary logistic regression analysis in a national cohort of 4917 women treated for primary breast cancer. In addition, statistical interactions between predictors and menopausal status were assessed in order to determine if their strength differed significantly as a function of menopausal status.

Results: Higher BMI, reduced physical function, reduced physical activity, and greater alcohol consumption were all statistically significantly associated with two or more tumor-related factors indicating a poorer prognosis. Interaction analysis revealed that BMI was significantly stronger associated with RoR among premenopausal women than among postmenopausal women (interaction ip = 0.048). Similarly, a significant association between RoR and physical function was only seen in the premenopausal population (ip = 0.008). This pattern was also seen between RoR and daily alcohol consumption, which only reached statistical significance in the total population and in premenopausal women (ip < 0.001).

Conclusion: Premenopausal women who are overweight and have poorer physical function have poorer prognosis at the time of diagnosis, suggesting the possible relevance of stratifying adjuvant treatment according to guidelines, BMI, and menopausal status.