Maimonides Evening of Research

Breast Surgical Oncology Fellow

Mukuhi Ng’ang’a, MD

Department of Surgery

Treatment outcomes of the KEYNOTE-522 regimen in an ethnically diverse patient population: a real world experience

Background

Pembrolizumab in combination with neoadjuvant chemotherapy (NACT) became standard of care for high risk, early stage triple negative breast cancer (TNBC) on July 26th 2021, as a result of the KEYNOTE-522 trial. Black women are disproportionately affected by TNBC with more advanced stage at diagnosis, however the KEYNOTE-522 did not collect race as a baseline demographic characteristic. This retrospective review evaluates response to pembrolizumab plus NACT in a racially diverse patient population.

Material and Methods

This is a single center, retrospective review of patients with stage II/III TNBC diagnosed between 08/2020 to 08/2023, treated with pembrolizumab plus NACT at Maimonides Medical Center. Exclusion criteria included age < 18 years, ER/PR/Her2 positivity, NACT without pembrolizumab, unreported race. Data were collected from EHR and analyzed using SPSS Statistics.

Results

50 patients met inclusion criteria, among whom 40 patients had complete information available for review. 52.5% (95% CI: 38% – 69%) of patients had a pCR. Median population age was 56 years. Population ethnic distribution was 47.5% African American, 30% Asian, 17.5% Caucasian and 5% Latin American. Our population had a higher number of patients with stage III disease (27.5 vs 24.7% in Keynote 522 trial) but this was not a significant determinant of pCR. 5 patients had progression of disease with the development of distant metastasis (2 whilst on treatment and 3 following completion of therapy). 3 patients had grade 3/4 adverse events (pembrolizumab associated endocrine and cardiac dysfunction). Lack of complete imaging response to treatment was highly associated with lack of pCR (p=0.003).

Conclusion

In this retrospective review of a racially diverse patient population, the pembrolizumab-NACT regimen was well tolerated with an acceptable side effect profile. While our rate of pCR is lower than the findings of the Keynote-522 trial; 52.5 % (95% CI: 38% – 69%) vs. 64.8% (95% CI: 59.9%-69.5%), our sample size is not large enough to detect a statistically significant difference. Additional data collection is in progress and future analysis will provide insight into a potential correlation between race and therapy response.