BACKGROUND

Mammary adipocyte size reflects both local excess of adiposity and adipose tissue dysfunction relevant to breast cancer biology.

OBJECTIVE

To identify modifiable factors that are associated with both traditional adiposity indicators and mammary adipocyte size in women with breast cancer, and to compare the individual and simultaneous effect of these factors.

METHODS

Data were collected prospectively from 160 consecutive breast cancer patients (biobank of a breast cancer reference center): factors that may influence body weight and composition (telephone interview), dietary intakes (DHQ-I) and adiposity measurements (anthropometric indices and mammary adipocyte size). Relationships between determinants of adiposity identified in the literature were summarized in a directed acyclic graph. Principal component analysis was conducted to capture dietary intakes from major nutrient intakes. Robust univariate and multivariable linear regression models were used to estimate the associations.

RESULTS

Menopausal status, ever smoking, tumour grade and higher weight at 18 years old were consistently associated with higher adiposity. Higher animal fat intakes was consistently associated with higher body mass index (BMI). High educational attainment was consistently associated with lower BMI and waist-to-height ratio. Higher physical activity was associated with lower adiposity and adipocyte cell size, whereas higher age was associated with higher adiposity and adipocyte cell size only in univariate models. Only menopausal status was consistently associated with higher mammary adipocyte size.

CONCLUSIONS

While excess adiposity is a complex condition that cannot be attributed to a single factor, menopausal status seems to be the main determinant of excess adiposity in women with breast cancer and the only independent determinant of mammary adipocyte size. Among lifestyle factors, ever smoking was the strongest independent determinant of higher adiposity, followed by high intakes of fats, particularly animal fats. If targeted efficiently, some of these modifiable factors could reduce the burden among breast cancer patients.