Durable Response to PD1 Inhibitor Pembrolizumab in a Metastatic, Metaplastic Breast Cancer

Area of Science:

• Oncology
• Immunotherapy
• Genomic Medicine

Background:

• Metaplastic breast cancer (MBC) is a rare, aggressive subtype characterized by triple-negative breast cancer (TNBC) features and poor prognosis.
• Chemotherapy resistance in MBC often results in recurrence and metastasis, highlighting the need for novel therapeutic strategies.
• Genomic profiling reveals molecular abnormalities in MBC, suggesting potential targets for therapy.

Observation:

• Metaplastic breast cancer (MBC) exhibits higher PD-L1 expression compared to other breast cancer subtypes.
• A patient with metastatic metaplastic triple-negative breast cancer (TNBC), featuring mesenchymal components and osseous differentiation, received treatment.
• The patient completed 2 years of pembrolizumab treatment.

Findings:

• The patient achieved and maintained no evidence of disease 32 months post-treatment, with a good quality of life.
• Pembrolizumab, an immunotherapy agent, demonstrated significant efficacy in this case of advanced metaplastic TNBC.
• Disease control with pembrolizumab and chemotherapy has been previously documented in MBC.

Implications:

• Further research into immunotherapy responses across diverse metaplastic breast cancer (MBC) subtypes is warranted.
• Incorporating immunotherapy into clinical trials is crucial for optimizing treatment strategies and improving outcomes in metaplastic breast cancer (MBC).
• This case supports the potential of targeted immunotherapy for aggressive, metastatic metaplastic triple-negative breast cancer (TNBC) patients.