Abstract 134P
Background
Recent trials have shown that the addition of PD-1 blockade to neoadjuvant chemotherapy improves pathologic complete response (pCR) in early-stage, high-risk, grade 3, estrogen receptor (ER)-positive, HER2-negative breast cancer. The level of tumor-infiltrating lymphocytes (TILs) is known to be associated with pCR in breast cancer. To differentiate pCR rates according to TIL levels and grade among ER+HER2- breast cancer patients, we investigated pCR rates in relation to TILs and grade in patients who received neoadjuvant chemotherapy (NAC).
Methods
Between January 2016 and December 2023, we retrospectively identified 376 patients with ER+HER2- breast cancer who underwent NAC followed by surgery. Histologic grade and TIL levels were examined using biopsied samples before NAC. High TIL cutoffs were set at 10%, 20%, and 30%.
Results
In all patients, the pCR rate was 5.3% (20/376) and 27 (7.2%) had grade 3 tumors. The pCR rate in the grade 3 group was 22.2%, significantly higher than the 4.0% rate in the grade 1/2 group. The grade 3 group had a higher mean TIL count compared to the grade 1/2 group. In the high TIL groups with cutoffs of 10%, 20%, and 30%, pCR rates increased with higher TIL levels and were significantly higher compared to low TIL groups: i) cutoff 10%, 1.9% vs. 9.5%; ii) cutoff 20%, 2.5% vs. 13.7%; iii) cutoff 30%, 2.8% vs. 18.3%. Within the grade 1/2 group, the pCR rate in the high TIL (≥30%) subgroup was 13.3%, whereas it was 33.3% in the grade 3 group.
Conclusions
Grade 3 tumors and increasing TIL levels were associated with elevated pCR rates among high-risk ER+HER2- breast cancer patients. Our findings support the notion that integrating PD-1 blockade into NAC could increase pCR rates in high-risk, grade 3 ER+HER2- breast cancer.
Legal entity responsible for the study
The authors.
Funding
Has not received any funding.
Disclosure
All authors have declared no conflicts of interest.