Risk of a second breast cancer associated with hormone-receptor and HER2/neu status of the first breast cancer.

OBJECTIVES Hormone-receptor (HR) and HER2/neu-receptor (HER2) status of breast tumors are important indicators for targeted therapies. We examine the association of receptor status and risk for a second breast cancer. METHODS We analyzed data on 106,331 women in the California Cancer Registry whose first cancer is locoregional invasive breast disease, diagnosed from 1999 through 2005, yielding 1,613 second primary breast cancers. Standardized incidence ratios (SIR) with 95% confidence intervals (CIs) were used to evaluate risk of second tumors, accounting for age at first diagnosis, duration at risk, and race/ethnicity. RESULTS Among non-Hispanic whites, HR-positive first tumors signal a reduction in risk for second breast cancers (SIR = 0.83, 95% CI: 0.77-0.89) whereas HR-negative status signals elevated risk (SIR = 1.48, 95% CI: 1.29-1.70). Asian/Pacific Islanders, African Americans, and Hispanics are at elevated risk of second breast cancers regardless of HR status of the first tumor. Hispanics with HR-negative first tumors are at greater risk than those with HR-positive disease (HR(-): SIR = 3.76, 95% CI: 2.97-4.71; HR(+): SIR = 1.86, 95% CI: 1.56-2.20). HER2 status does not differentiate risk for second tumors in any group examined. CONCLUSIONS HR status of a first breast cancer is a marker for risk of a second breast cancer. HER2 status does not seem to be a marker of risk for a second breast cancer. Risk differences across race/ethnic groups by HR status suggest heterogeneity of breast cancers across race/ethnicity. IMPACT These data suggest that HR status may be helpful in shaping strategies to reduce risk of a second breast cancer, while HER2 status seems uninformative for this purpose.