(HealthDay News) — Molecular subtypes are predictors of breast cancer mortality and can play a role in determining the best course of treatment to follow, according to a study published online Sept. 18 in Cancer Epidemiology, Biomarkers & Prevention.

Reina Haque, Ph.D., M.P.H., from Kaiser Permanente Southern California in Pasadena, and colleagues examined 934 female members of an integrated health care delivery system who were newly diagnosed with invasive breast cancer between 1988 and 1995. Patients were followed through 2008. Tumors were subtyped molecularly as follows: luminal A; luminal B; basal-like; and human epidermal growth factor receptor 2 (HER2)-enriched.

The researchers found that, over the 21 years of the study period, 223 women (23.9 percent) died due to breast cancer. Women with HER2-enriched (hazard ratio [HR], 2.56) and luminal B tumors (HR, 1.96) had roughly a two-fold increased adjusted risk of breast cancer mortality compared to women with luminal A tumors. However, risk of late mortality persisted in women with luminal A tumors.

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“The findings of this study indicate that it is important to consider breast cancer molecular subtypes in determining the optimal treatment for women with breast cancer,” Haque said in a statement. “Women with luminal A tumors — the least aggressive but most common cancerous breast tumor — could benefit from extended treatment to improve their chances for long-term survival.”

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