Approximately 1 of 5 patients with early-stage breast cancer (ESBC) express an amplified HER2 gene and over-expression of a HER2 protein. Researchers from St Vincent’s University Hospital of Dublin shared their findings at the virtual 2021 ESMO Congress to support improved survival and adjuvant anti HER-2 therapy for ESBC which can prevent rather than delay the disease.

“We hypothesized that the proportion of all metastatic breast cancer (mBC) which is HER-2+ should have decreased since the introduction of widespread anti -ER2 adjuvant treatment for ESBC,” explained Jose Javier Berenguer-Pina, MD, St Vincents University Hospital, Dublin, and co-researchers.

Alterations from HER2 expression are known to be associated with a higher frequency of metastasis, more aggressive behavior, and a substantial therapeutic benefit from anti-HER2 targeted adjuvant and neoadjuvant therapies.

Researchers conducted a retrospective audit of all patients with a pathological diagnosis of mBC in two cohorts from 2000-2002 (before routine adjuvant HER2 therapy was standardized) and 2018-2020. HER2+ defined by FISH amplification and/or 3 or more immune-histochemistry.

231 and 183 patients were in the 2000-2002 and 2018-2020 cohorts, respectively. Findings show that the proportion of all mBC which was HER-2+ has reduced from 33.76% to 16.69% during that time, a difference which is highly statistically significant (Fischer exact test p<0.0).

“The proportion of mBC which is HER2+ has decreased substantially since the introduction of anti HER2 therapy. We have previously reported that the percentage of HER2 altered mBC which is diagnosed as ‘de novo’ has increased during this time, and that de novo mBC has a better prognosis,” continued Dr Berenguer-Pina, et al.

From these results, researchers believe improvements in breast cancer survival may be correlated with a decreased incidence of HER2+ mBC and a shift within HER2+ mBC to better prognosis de novo disease.

“Anti HER2 therapy in ESBC has produced a substantial alteration in the molecular profile and prognosis of metastatic breast cancer,” concluded Dr Berenguer-Pina, et al. – Alexa Stoia