HealthDay News – Obesity is positively associated with estrogen receptor- (ER) positive breast cancer mortality in pre-/peri-menopausal women, according to research presented at the American Society of Clinical Oncology (ASCO) annual meeting.
“Obesity is reportedly associated with worse prognosis in early breast cancer. But, this association could depend strongly on estrogen receptor positivity and ovarian activity (or young age),” explained Hongchao Pan, PhD, and researchers.
Using data from the Early Breast Cancer Trialists’ Collaborative Group study, Pan and colleagues analyzed the independent effects of body mass index on outcome. Data were included for 80,000 patients in 70 trials, with mean follow-up of eight years.
BMI correlated positively with breast cancer mortality in 60,000 women with ER-positive disease, including women who were pre-, per- and post-menopausal. After adjustment for tumor characteristics, the correlation persisted only for the 20,000 pre-/per-menopausal patients with ER-positive disease (breast cancer mortality rate ration for BMI ≥30 versus 20 to 25 kg/m², 1.34; P<0.00001).
In contrast, little association persisted in 40,000 post-menopausal patients with ER-positive breast cancer (rate ratio, 1.6; P=0.12). For the 20,000 patients with ER-positive diseases, little correlation persisted between BMI and breast cancer mortality. The association no longer persisted after adjustment for tumor diameter and nodal status.
“In women with early breast cancer, obesity appears strongly independently related to breast cancer mortality only in pre/peri-menopausal ER-positive disease,” wrote the researchers.