The influence of metabolic factors and ethnicity on breast cancer risk, treatment and survival: The Oslo ethnic breast cancer study.

BACKGROUND: Breast cancer risk remains higher in high-income compared with low-income countries. However, it is unclear to what degree metabolic factors influence breast cancer development in women 30 years after immigration from low- to a high-incidence country. METHODS: Using Cox regression models, we studied the association between pre-diagnostic metabolic factors and breast cancer development, and whether this association varied by ethnicity among 13,802 women participating in the population-based Oslo Ethnic Breast Cancer Study. Ethnic background was assessed and pre-diagnostic metabolic factors (body mass index, waist:hip ratio, serum lipids and blood pressure) were measured. A total of 557 women developed invasive breast cancer, and these women were followed for an additional 7.7 years. RESULTS: Among women with an unfavorable metabolic profile, women from south Asia, compared with western European women, had a 2.3 times higher breast cancer risk (HR 2.30, 95% CI 1.18-4.49). Compared with the western European women, the ethnic minority women were more likely to present with triple-negative breast cancer (TNBC) (OR 2.11, 95% CI 0.97-4.61), and less likely to complete all courses of planned taxane treatment (OR 0.26, 95% CI 0.08-0.82). Among TNBC women, above-median triglycerides:HDL-cholesterol (>0.73) levels, compared with below-median triglycerides:HDL-cholesterol (≤0.73) levels, was associated with 2.9 times higher overall mortality (HR 2.88, 95% CI 1.02-8.11). CONCLUSIONS: Our results support the importance of metabolic factors when balancing breast cancer prevention and disease management among all women, and in particular among non-western women migrating from a breast cancer low-incidence to a high-incidence country.

Exploring the effects of lifestyle on breast cancer risk, age at diagnosis, and survival: the EBBA-Life study.

PURPOSE: Whether an unfavorable lifestyle not only affects breast cancer risk, but also influences age at onset of breast cancer and survival, is under debate. METHODS: In a population-based cohort, the Energy Balance and Breast Cancer Aspects throughout life (EBBA-Life) study, a total of 17,145 women were included. During follow-up, 574 women developed invasive breast cancer. Breast cancer cases were followed for an additional 9.1 years. Detailed medical records were obtained. Cox's proportional hazard regression models were used to study the association between pre-diagnostic lifestyle factors (weight, physical activity, alcohol use, smoking, and hypertension), breast cancer risk, age at diagnosis, and survival. RESULTS: At study entry, 34.3% of the participating women were overweight and 30.7% were physically inactive. Mean age at breast cancer diagnosis was 58.0 years, and 78.9% of the tumors were estrogen receptor positive. Among menopausal women who did not use hormone therapy and had an unfavorable lifestyle (3-5 unfavorable factors), compared with women who had a favorable lifestyle, we observed a twofold higher risk for postmenopausal breast cancer (hazard ratio [HR] 2.13, 95% confidence interval [CI] 1.23-3.69), and they were 3.4 years younger at diagnosis (64.8 versus 68.2 years, P = 0.032). Breast cancer patients with an unfavorable lifestyle, compared with patients with a favorable lifestyle, had almost a two times higher overall mortality risk (HR 1.96, 95% CI 1.01-3.80). CONCLUSIONS: Our study supports a healthy lifestyle improving breast cancer prevention, postponing onset of disease, and extending life expectancy among breast cancer patients.

Impact of pre-diagnostic triglycerides and HDL-cholesterol on breast cancer recurrence and survival by breast cancer subtypes.

BACKGROUND: High triglycerides and low levels of high density lipoprotein (HDL)-cholesterol are observed to promote tumor growth. However, whether breast cancer heterogeneity may explain the contradictory influence of triglycerides and cholesterol observed on breast cancer prognosis remains unclear. METHODS: A population-based survival study among 464 breast cancer cases identified within the Tromsø study was conducted. Pre-diagnostic triglycerides, total-cholesterol and HDL-cholesterol were measured, and detailed clinical and histopathological data were obtained. Using tissue microarray, all breast cancer cases were reclassified into the following subtypes: Luminal A, Luminal B, HER2-enriched, and triple negative breast cancer (TNBC). Multivariable Cox proportional hazards regression models were used to study the associations between pre-diagnostic lipids and breast cancer recurrence, mortality, and survival. RESULTS: A total of 464 breast cancer patients, with mean age at diagnosis of 57.9 years, were followed for a mean 8.4 years. TNBC patients in the highest tertile of triglycerides (≥ 1.23 mmol/l) had 3 times higher overall mortality compared to TNBC patients in the lowest tertile (≤ 0.82 mmol/l) (HR 2.99, 95% CI 1.17-7.63), and the 5-year overall survival was 19% lower for TNBC patients in the highest vs. lowest tertile of triglycerides (65% vs. 84%). TNBC patients in the highest tertile of the HDL-cholesterol/total-cholesterol ratio (≥0.35), compared to those in the lowest tertile (≤0.27), had a 67% reduced overall mortality risk (HR 0.33, 95% CI 0.12-0.89). No associations were observed between lipids and prognostic outcome among breast cancer patients overall, or among patients with luminal A and luminal B subtypes. Among HER2-enriched patients, pre-diagnostic triglyceride level was inversely associated with overall mortality. CONCLUSION: Our study suggests that pre-diagnostic triglycerides and the HDL-cholesterol/total-cholesterol ratio may independently provide unique information regarding prognostic outcome among triple negative breast cancer patients. However, a small sample size underlines the need for additional studies.