Human epidermal growth factor receptor 3 expression in patients with epithelial ovarian cancer: a potential target for ovarian mucinous and clear cell carcinoma.

Background: Human epidermal growth factor receptor 3 (HER3), a tyrosine kinase belonging to the HER family, is a known target for cancer therapy; recently, an anti-HER3 antibody-drug conjugate (ADC) is developing. To understand HER3 expression in epithelial ovarian cancer (EOC), this study was conducted.

Methods: We investigated the expression of HER3 in 202 patients with EOC using immunohistochemistry (IHC), and the association between HER3 expression, clinicopathological features, prognosis, and treatment timing.

Results: Of all the cases, 55.4% had a HER3 IHC score ≥ 1 + . In particular, 78.0% of the patients with clear cell carcinoma (CCC) and 87.9% of the patients with mucinous carcinoma (MC) had a HER3 IHC score ≥ 1 + . Regarding clinicopathological features, early disease stage, feasibility of primary debulking surgery, no residual tumor, and low CA125 levels were more frequently observed in patients with a HER3 IHC score ≥ 1 + . Furthermore, a HER3 no-expression showed a significant association with a relatively short progression-free survival (PFS). And, for patients with mucinous carcinoma, those with a HER3 IHC score ≥ 1 + had poorer PFS and overall survival than those with a HER3 no-expression (no statistically significant difference). In addition, we analyzed HER3 expression at primary tumor and recurrence tumor in same patients. Thus, we observed the HER3 IHC score tended to change from 0 to ≥ 1 + in recurrence cases compared with primary cases.

Conclusions: These observations suggested that patients with MC, CCC and recurrence of all histological type may potentially benefit from future clinical trials of HER3-directed therapies.