Modified IHC4 score predicts prognosis but not chemotherapy survival benefit in young women with HR-positive, HER2-negative early breast cancer: A Hospital-Based Cohort study

Background: We aimed to determine whether a modified IHC4 score has predictive and prognostic significance in young patients with hormone receptor (HR) positive- and human epidermal growth factor receptor 2 (HER2)-negative breast cancer. Methods Data of 230 breast cancer patients (< 40 years old, HR positive, HER2 negative, T1–3, and N0–1 microinvasion) who underwent surgery at the National Taiwan University Hospital from 2009 to 2018 were retrospectively collected. Immunohistochemical staining data were collected, and the associated modified IHC4 score was calculated. The association between patient characteristics and breast cancer events was analyzed. Results Prognosis at the median follow-up period of 5.66 years was better in the mIHC4 low-risk group than in the mIHC4 intermediate and high-risk groups. The hazard ratios were 10.89 (95% CI, 1.083–109.5; p = 0.043) and 18.49 (95% CI, 1.316–259.8; p = 0.031) in the intermediate and high-risk groups, respectively, compared with those in the low-risk group for the occurrence of breast cancer events. Adjuvant chemotherapy did not result in differences in breast cancer event-free survival among the three mIHC4 risk groups. Conclusions The modified IHC4 risk score has a prognostic value in young breast cancer patients with HR-positive and HER2-negative disease, but has no predictive value for adjuvant chemotherapy. Adjuvant chemotherapy may not be effective in this population, warranting the development of new treatment strategies in these patients.