Obesity and risk of the less commonly diagnosed subtypes of breast cancer

A set of common epidemiologic risk factors have been associated with the risk of breast cancer despite of its molecular sub-classifications. We implemented a case series study with the primary objective of evaluating if obesity is associated with the diagnostic risk of "ER+ and/or PR+, HER2+", "ER-/PR-, HER2-", or "ER-/PR-, HER2+" relative to the most commonly diagnosed subtype of breast carcinoma, "ER+ and/or PR+, HER2-".

Demographic, clinical and pathologic data were collected from existing databases. The statuses of HER2/neu biomarker and hormone receptors were dichotomized as either positive or negative. Immunohistochemical staining was used to assess the prevalence of different subtypes. Body mass index was calculated from weight and height data collected at the time of consultation.

Findings from the present study suggest that excess body weight decreases the diagnostic risk of "ER-/PR-, HER2-", or "ER-/PR-, HER2-" relative to "ER+ and/or PR+, HER2-". Obese and overweight women are more likely to be diagnosed with to "ER+ and/or PR+, HER2-", the subtype that has best prognosis and mostly associated with personal lifestyle. Weight gain with the population attributable-risk factor of 21.3% contributes the most to the incidence of invasive post menopausal breast cancer. Younger pre-menopausal women were more likely to be diagnosed with "ER+ and/or PR+, HER2+". In younger women biology of breast cancers with positive expression for hormone receptors and epidermal growth factor is a complex that extends beyond the currently assessed prognostic markers.