Recurrence score (RS) differences between primary and second-primary breast cancer (BC): Exploratory analysis of the Clalit Health Services (CHS) registry.

Abstract

e12587 Background: In the phase 3 TAILORx study, the first invasive disease-free survival event (in all arms) was often opposite BC or other second primary cancer. Our goal was to investigate differences in the 21-gene RS results between the primary BC and a second primary BC, as well as the association with clinicopathological characteristics. Methods: This analysis of the prospectively-designed CHS registry included all CHS pts with estrogen receptor (ER)+ HER2-negative BC who underwent RS testing between 1/2006 and 6/2019 and for whom ≥2 RS results were identified which were > 1 year apart. Results: Of the 10,244 RS assays ordered in this time frame, 371 involved pts for whom the assay was performed at least twice. Our analysis focused on the 42 pts for whom the assays were performed > 1 year apart. All pts were females; 76% were initially diagnosed with node-negative BC; median (interquartile range [IQR]) age at first diagnosis was 56 (43-64) yrs. Tumor characteristics for the first and subsequent primary BC are presented (Table). The median time (IQR) between the first and latest RS assay was 4.5 (2.9-6.4) yrs. In 28 pts (67%), the latest primary BC was ipsilateral and in 14 (33%) it was contralateral. The median (IQR) difference between the first and latest RS value was 7 (1-12). The second/third primary BC had higher RS than the first BC in the majority (76%) of pts. Higher RS in the latest primary BC (compared to the first primary BC) was more common when the latest primary BC was ipsilateral than when it was contralateral (86% vs 57%, P= 0.04). Conclusions: In ER+ HER2-negative BC pts, second/third primary BC is generally associated with higher RS result (compared to the first primary BC), particularly if the later primary BC is ipsilateral. [Table: see text]