Healthy lifestyle indices are associated with breast cancer immunophenotypes in women

Multiple modifiable lifestyle risk factors are independently associated with breast cancer (BC); however, evidence lacks regarding the joint relationship between lifestyle components and BC immunophenotypes.

We aimed to assess the association among adherence to healthy lifestyle indices and BC immunophenotypes in women.

We conducted a secondary analysis of data from a study performed between 2007 and 2011, comprising 1045 cases and 1030 population controls. We retrieved information on estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor 2 (HER2) expression from medical records to classify BC as luminal (ER+ and/or PR+/HER2-), HER2+ (ER+/- and/or PR+/-/HER2+), or triple negative (TN) (ER- and PR-/HER2-). Through direct interviews, we obtained lifestyle variable information such as diet, physical activity, as well as tobacco and alcohol consumption. We evaluated compliance with the Healthy Lifestyle Index Score (HLIS) and the Healthy Behavior Index (HBI). We used non-conditional logistic regression models to assess the association between BC immunophenotypes and the indices.

Women with higher adherence to the HLIS had a 23 % lower probability of BC (Odds ratio [OR]_{Tertil (T)3vsT1} = 0.77; 95%Confidence Interval [CI]: 0.60, 0.99; p-trend = 0.030), while those adhering to the HBI showed a 68 % reduction (OR _T3vsT1 = 0.32; 95%CI: 0.24, 0.42; p-trend = 0.000). These associations remained negative across all BC immunophenotypes.

Adherence to healthy lifestyle indices might prevent BC. Further research is warranted to elucidate the intricate interplay among lifestyle factors and BC risk across diverse populations and immunophenotypes.