The influence of ER on small HER2-positive invasive breast cancers.

Abstract

1586 Background: There is controversy regarding the risk of recurrence of the node-negative, HER2-positive pT1a-b tumors. We have shown considerable variation in survival of HER2-positive tumors of all sizes. We now examine the HER2-positive breast cancers with regard to ER status, node-status, and tumor size. Methods: Using the California Cancer Registry 2000-2007, we studied 16,958 cases of stages 1-3, HER2-positive primary invasive breast cancer. Kaplan-Meier cause-specific 5-year overall survival (OS) was computed and the log-rank test was used to compare survival between node-positive and node-negative tumors within the T1a, T1b, T1c, and T2 categories. Cox-proportional hazards analysis was used to determine the effect of ER/PR/HER2 subtype within each tumor size category for the node-positive tumors after adjusting for age, race/ethnicity, stage, grade, and socioeconomic status. Anti-HER2 treatment information was not available. Hazard ratios (HR) and 95% confidence intervals were computed. Results: For all tumor sizes, survival was statistically significantly better for negative node-tumors than for node-positive tumors (p < 0.001). Node-negative T1a, T1b, and T1c tumors had 5-year survival of 99%, 98%, and 97% respectively. There were 7,430 node-positive cases and survival was 93% for T1a, 94% for T1b, and 90% for T1c. No variables were associated with risk of death for the T1a and T1b tumors. Compared with the ER-/PR-/HER2+ subtype (the molecularly defined HER2-positive subtype), the ER+/PR+/HER2+ (HR = 0.33; 95% CI = 0.22-0.49) and ER+/PR-/HER2+ (HR = 0.49; 95% CI = 0.30-0.81) subtypes were associated with a reduced risk of death for T1c and T2 tumors. Conclusions: It is not surprising that node-negative breast cancers have better survival than node-positive cases. We found that for HER2-positive, node-negative, T1a, T1b, and T1c tumors, 5-year OS is excellent and for node-positive cases, it is only slightly lower but still 90% or greater. For tumors less than 10mm, ER/PR/HER2 subtype does not appear to influence survival. For larger tumors, ER-positivity reduces the risk of death when compared with the molecularly defined HER2-positive subtype, suggesting that ER rather than HER2 has greater influence on OS. No significant financial relationships to disclose.