HER2-positivity is often associated with poor survival. The purpose of this study is to determine if there are differences in mortality among the HER-positive subtypes when stratified by stage and race/ethnicity.

Methods: Using the California Cancer Registry for years 2000–2010, we examined 99,897 cases of stages 1–3 ER+/PR+/HER2− and all HER2-positive first primary female invasive breast cancers. Race/ethnicity was defined as white, black, Hispanic, and Asian/Pacific Islander (API). Kaplan-Meier (KM) and the Log-Rank test were used to compute 6-year survival. Cox proportional hazards was used to assess the risk of mortality of each of the HER2-positive subtypes when compared with the ER+/PR+/HER2− subtype (the most common subtype). All analyses were adjusted for age, grade, year of diagnosis (<2007, 2007+), and socioeconomic status and run separately by race for stages 1, 2, and 3.

Results: For all stages combined, of the subtypes comprising the luminal B-HER2 positive category, the ER+/PR+/HER2+ had the best survival (85%), only 2% less than the ER+/PR+/HER2−.

When compared with the ER+/PR+/HER2− subtype, no difference in KM survival was noted for stage 1 luminal B (ER+/PR+/HER2+;ER+/PR−/HER2+; ER−/PR+/HER2+). Both had 90% 72-month survival. The ER−/PR−/HER2+ had 88% survival (p < 0.02).

For stage 2, luminal B had 83% survival and ER−/PR−/HER2+ had 76% survival. Both were significantly different (p < 0.001) from the ER+/PR+/HER2− subtype (86%).

The luminal B had 68% survival and the ER−/PR−/HER2+ had 55% survival for stage 3. Both were statistically significantly worse (p <.006) than the ER+/PR+/HER2− (72%).

Adjusted mortality for the ER+/PR+/HER2+ was only increased for blacks in stage 1 (HR = 1.59; 95%CI=1.09–2.33). Mortality for the ER−/PR−/HER2+ was increased for whites in all stages; for blacks in stages 1 (HR = 1.82; 95%CI=1.11–3.00) and 3 (HR = 1.90; 95%CI=1.36–2.66); for Hispanics in stages 2 (HR = 1.58; 95%CI=1.28–1.95) and 3 (HR = 2.19; 95%CI=1.73–2.78); and APIs only in stage 2 (HR = 1.70; 95%CI=1.31–2.19)

Year of diagnosis made no difference in risk of mortality in stage 1 for any race. For stage 2, blacks had slightly reduced mortality if diagnosed in 2007 or later, and for stage 3, all races except blacks had reduced risk of mortality when diagnosed in 2007 or later.

Conclusions:  

  • 1. There is variation in survival among the luminal B-HER2 positive subtypes.

  • 2. The driving force behind the increased mortality of the HER2 positive subtype is the ER−/PR−/HER2+ subtype, the molecularly defined HER2 overexpressing subtype.

  • 3. Year of diagnosis does not influence survival in stage 1 for any race.

  • 4. There are differences in mortality among the HER2 positive subtypes when stratifying by stage and race and adjusting for age, grade, year of diagnosis, and SES.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P3-09-02.