257P - The characteristics of HER2-positive microinvasive breast cancer and the necessity of chemotherapy and anti-HER2 therapy in these patients: A real-world study

Background

The prognosis of microinvasive breast cancer (MIBC) is between ductal carcinoma in situ and T1aN0 stage tumors. We conducted this real-world study to explore the prognosis of human epidermal factor receptor 2 (HER2)-positive MIBC, as well as to find out whether chemotherapy and anti-HER2 therapy could improve outcome in this population.

Methods

Patients who received radical surgery and were diagnosed with lymph node-negative HER2-positive MIBC at the National Cancer Center in China from January 2010 to December 2019 were consecutively enrolled. The invasive components were confirmed HER2-positive by pathologists from our center. The exclusion criteria included: 1) distant metastasis before surgery; 2) HER2 status of the invasive components was unknown. Clinicopathologic characteristics and follow-up outcome data were collected.

Results

A total of 121 patients were included. The median age was 51 years old, and the median follow-up time was 68.3 months. Twenty-four patients (19.8%) received adjuvant chemotherapy (CT), of which 7 patients received CT combined with trastuzumab. Among these 24 patients, 17 patients were aged ≤ 50, and 20 patients were estrogen receptor (ER) negative. In total, 5 patients experienced recurrence (2 in situ breast recurrence, 3 distant metastasis), all within 3 years after surgery. The 3-year disease free survival (DFS) rate and 5-year DFS rate were all 95.9%. Univariate analysis showed that patients aged ≤ 50 might have worse outcomes than those aged > 50 (5-year DFS rate 92.5% versus 98.5%, p=0.098). Using propensity score matching, patients who received CT with or without trastuzumab were matched with those who did not receive CT in a 1:2 ratio based on age and ER status. Patients who received CT with or without trastuzumab showed a trend of increase in 5-year DFS rate compared to those who did not receive CT (100% vs 89.6%, p=0.106).

Conclusions

HER2-positive MIBC had a relatively good prognosis. For patients with risk factors of relapse, CT and trastuzumab might decrease recurrence, so adjuvant CT and anti-HER2 therapy could be considered in this population.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

The authors.

Funding

Has not received any funding.

Disclosure

All authors have declared no conflicts of interest.