Objective:

To report a case of severe aplastic anemia following neoadjuvant pembrolizumab and chemotherapy in a patient with triple-negative breast cancer.

Approach:

• Patient Background: A 54-year-old woman with triple-negative breast cancer treated with neoadjuvant pembrolizumab and chemotherapy developed severe pancytopenia post-surgery.
• Diagnostic Evaluation: Bone marrow biopsy indicated generalized bone marrow suppression; high-dose corticosteroids were initiated without hematologic response.
• Further Testing: Tests revealed parvovirus B19 infection, leading to the initiation of intravenous immunoglobulin therapy.
• Outcome: The patient experienced rapid hematologic recovery and completed adjuvant radiotherapy, remaining disease-free at 20-month follow-up.

Key Findings:

• Severe aplastic anemia can occur following neoadjuvant pembrolizumab and chemotherapy in triple-negative breast cancer.
• It is crucial to distinguish between infectious bone marrow suppression and immune-related hematologic toxicity for effective management.
• Intravenous immunoglobulin therapy was effective in treating parvovirus B19 infection in this case.

Interpretation:

This case highlights the importance of thorough diagnostic evaluation in patients with severe cytopenias after immunotherapy.

Limitations:

• The rarity of hematologic adverse events complicates management and may lead to diagnostic delays specific to this case.
• There is limited data from clinical trials on hematologic toxicities associated with immunotherapy, impacting treatment decisions.

Conclusion:

This case illustrates the complex relationship between infection and immune checkpoint inhibition, emphasizing the need for accurate diagnosis in treatment decisions.