Characterization of HER2‐low breast cancer in young women with germline BRCA1/2 pathogenetic variants: Results of a large international retrospective cohort study

Abstract

BackgroundBreast cancer (BC) in women aged ≤40 years carrying germline pathogenetic variants (PVs) in BRCA1/2 genes is infrequent but often associated with aggressive features. Human epidermal growth factor receptor 2 (HER2)‐low‐expressing BC has recently emerged as a novel therapeutic target but has not been characterized in this rare patient subset.MethodsWomen aged ≤40 years with newly diagnosed early‐stage HER2‐negative BC (HER2‐0 and HER2‐low) and germline BRCA1/2 PVs from 78 health care centers worldwide were retrospectively included. Chi‐square test and Student t‐test were used to describe variable distribution between HER2‐0 and HER2‐low. Associations with HER2‐low status were assessed with logistic regression. Kaplan–Meier method and Cox regression analysis were used to assess disease‐free survival (DFS) and overall survival. Statistical significance was considered for p ≤ .05.ResultsOf 3547 included patients, 32.3% had HER2‐low BC, representing 46.3% of hormone receptor–positive and 21.3% of triple‐negative (TN) tumors. HER2‐low vs. HER2‐0 BC were more often of grade 1/2 (p < .001), hormone receptor–positive (p < .001), and node‐positive (p = .003). BRCA2 PVs were more often associated with HER2‐low than BRCA1 PVs (p < .001). HER2‐low versus HER2‐0 showed better DFS (hazard ratio [HR], 0.86; 95% CI, 0.76–0.97) in the overall population and more favorable DFS (HR, 0.78; 95% CI, 0.64–0.95) and overall survival (HR, 0.65; 95% CI, 0.46–0.93) in the TN subgroup. Luminal A–like tumors in HER2‐low (p = .014) and TN and luminal A‐like in HER2‐0 (p = .019) showed the worst DFS.ConclusionsIn young patients with HER2‐negative BC and germline BRCA1/2 PVs, HER2‐low disease was less frequent than expected and more frequently linked to BRCA2 PVs and associated with luminal‐like disease. HER2‐low status was associated with a modestly improved prognosis.

Unraveling the clinicopathological and molecular changes induced by neoadjuvant chemotherapy and endocrine therapy in hormone receptor-positive/HER2-low and HER2-0 breast cancer

“…Results are quite heterogeneous in the literature. 24 , 25 For this reason, two meta-analyses were recently conducted to shed light on this topic. Overall, in early-stage HR+/HER2-negative disease, HER2-low BC was less associated with pCR, but showed an association with slightly better disease-free survival and OS, in comparison to HER2-0.…”