HER2 exon 27 mutations predict worse survival of breast cancer patients, especially in HER2-negative patients

Activating human epidermal growth factor receptor 2 (HER2) gene mutation in bone metastases from breast cancer

In addition to amplification, point mutations of the human epidermal growth factor receptor 2 (HER2) gene (ERBB2) have been shown to activate the corresponding signaling pathway in breast cancer. The prevalence of ERBB2/HER2 mutation in bone metastasis of breast cancer and the associated phenotype are not known. In this study, bone metastases from breast cancer patients (n = 231) were analyzed for ERBB2/HER2 mutation. In 7 patients (3%; median age 70 years, range 50-83 years), gain-of-function mutations of ERBB2/HER2 were detected. The most frequent mutation was p.L755S (71%). In 29% of mutated cases, p.V777L was found. Lobular breast cancer was present in 71% of mutated cases (n = 5) and in 49% of all samples (n = 231; p = 0.275). Mutation frequency was 4.4% in the lobular subgroup and 17.4% in the pleomorphic subtype of lobular cancer (n = 23), respectively. All but one mutated lobular cancers were of the pleomorphic subtype (p = 0.006). Mutated cancers belonged either to the luminal (n = 4) or to the triple-negative types (n = 3). With regard to protein expression and gene amplification, HER2 was negative in all mutated cases. Among the 14% of metastatic luminal cancers with estrogen receptor gene (ESR1) mutation, conveying resistance against aromatase inhibitors, no concomitant ERBB2/HER2 mutation occurred. We conclude that activating HER2 mutation is present in about 3% of bone metastases from breast cancers, with significantly higher rates in the pleomorphic subtype of lobular cancer. Since mutated cases appear to be HER2-negative by conventional testing, the opportunity for specific anti-HER2 therapy may be missed.

HER2 exon 27 mutations predict worse survival of breast cancer patients, especially in HER2-negative patients

The aims of this study were to assess the prognostic value of the HER2 exon 27 mutations in breast cancer patients. Genomic DNA was isolated from peripheral blood leukocytes, and then HER2 exon 27 mutations were detected by direct sequencing. Survival curves were estimated by Kaplan-Meier curves and the differences between the curves were compared by log-rank tests. A total cohort of 892 female patients with operable primary breast cancer was included in this study. The median follow-up was 47 months. Of these 892 patients, 3.7% (33/892) had HER2 exon 27 mutations. Patients with the HER2 exon 27 mutations had a significant worse recurrence-free survival (RFS, unadjusted hazard ratio [HR] 2.42; 95% CI: 1.05-5.58; P = 0.032) and distant recurrence-free survival (DRFS, unadjusted HR 2.81; 95% CI: 1.21-6.50; P = 0.012) than the patients with the wild-type exon 27. Among the 673 patients with negative HER2 expression, 24 mutants were found. Patients with the HER2 mutations showed a worse RFS (unadjusted HR 5.08; 95% CI: 2.14-12.02; P < 0.001) and DRFS (unadjusted HR 5.62; 95% CI: 2.36-13.40; P < 0.001) than those patients with the wild-type exon 27. Furthermore, the mutations remained as unfavorable independent predictors for RFS and DRFS. Breast cancer patients with HER2 exon 27 mutations have a worse survival, especially in HER2-negative patients. HER2-negative patients with HER2 exon 27 mutations are potential subgroup of breast cancer patients benefiting from HER2-targeted therapy in future.