288P - Prognostic factors in nonmetastatic HER2 ‘low’ & HER2 ‘negative’ breast cancer: Single institute experience

Background

Human epidermal growth factor-2 (HER2) low breast cancer is a novel entity that differs from HER2-negative ones. We evaluated prognostic factors in HER2 low & compared with HER2-negative breast cancer retrospectively.

Methods

Estrogen receptor (ER) +/ progesterone receptor (PR) +, HER2 low and HER2-negative patients without distant metastasis were included.

Results

444 (HL n:209, HN n:235) patients were evaluated. Median follow-up was 47 months. Most (59%) were postmenopausal. 121 (27.3%) had immunohistochemistry (IHC) score 1, 88 (19.8%) had IHC score 2 (SISH -). Mean age was 54.5 vs 53.3 years. Stage 2 (35.8%) & grade 2 (49.3%) were most common. Median ER/PR/ki67 were 95/60/25% for HER2 low & HER2 negative. 375 patients had chemotherapy, most (86%) had adjuvant chemotherapy. 40 (9%) had relapse & most (n: 31, 77.5%) had distant relapse. HER2-negative patients tended to have higher relapse rate (11.5% vs 6.2%, p:0.053). 5 year-disease free survival (DFS) was shorter for patients with HER2 negative (83.4% vs 90.8%), positive lymph nodes ≥10 (63.2% vs 92.3%), ECE + (75.4% vs 91.5%), ki67≥20% (70.2% vs 83.9%) (p: 0.021, p:0.008, p:0.004, p:0.026) (Table). Stage was inversely correlated with DFS (p: 0.001). HER2 status [HR: 0.43 (95% Cl: 0.20 –0.94), p=0.035] & ki67 [OR: 2.99 (95% Cl: 1.21–7.36), p=0.017] were significant prognostic factors in multivariate analysis. Overall survival (OS) data was immature. Table: 288P

Survival according to clinical & pathological features

Conclusions

HER2 low breast cancer patients, especially with ki67 <20% had better DFS, Most patients had IHC score 1.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

Clinical of Medical Oncology.

Funding

Has not received any funding.

Disclosure

All authors have declared no conflicts of interest.