Immune Checkpoint Inhibitor Pneumonitis: Implications for Definitive Breast Cancer Reconstruction.

Checkpoint inhibitor-associated pneumonitis (CIP) is a rare but potentially life-threatening immune-related adverse event in patients receiving immunotherapy. Its occurrence especially in the immediate postoperative period following major reconstructive breast surgery has not been previously described and poses unique diagnostic and management challenges.We report the case of a 59-year-old BRCA+ female with history of right-sided triple-negative breast cancer status-post bilateral mastectomy with negative right sentinel lymph node biopsy who had undergone bilateral abdominal based free flap breast reconstruction over 1 month after the completion of pembrolizumab, an immune checkpoint inhibitor (ICI). This patient subsequently had worsening postoperative respiratory function to the point of being high-flow nasal cannula dependent on rest. Appropriate postoperative etiologies (i.e., pulmonary embolism, pneumonia, etc) were ruled out, and CIP was diagnosed with supporting imaging. The patient recovered with a treatment combination of corticosteroids, IVIG, and MMF, and the patient was discharged home on supplemental oxygen via nasal cannula on postoperative day 15. She has since followed up only on room air and excellent postreconstructive outcomes.This case report underscores a highly surgically relevant topic of breast cancer reconstructive surgery timing and clinical management of those patients treated with ICI. Especially with personalized immunomodulator chemotherapy regimens becoming more prevalent, breast and reconstructive surgeons, alike, should be aware of this likely growing phenomenon of CIP.