A Case Report of Ribociclib-Induced Pneumonitis

ABSTRACT

Palbociclib, abemaciclib and ribociclib are cyclin-dependent kinase 4/6 (CDK 4/6) inhibitors used in the current treatment of HR-positive, HER2-negative metastatic breast cancer.1.2 As CDK 4/6 inhibitors are becoming more common it is important to be aware of some potentially fatal side effects. A 54-year-old woman with stage III breast cancer with prior mastectomy currently on hormonal and immunotherapy with anastrozole, ribociclib and goserelin presented with fever and shortness of breath. The patient became febrile with a negative COVID-19 test, and was treated for community acquired pneumonia. The fevers persisted despite antibiotics. CBC notable for leukopenia and uptrending absolute eosinophil count of 280 cells per microlitre. A chest CT scan revealed scattered, predominantly peripheral ground glass opacities in the bilateral upper, bilateral lower, and right middle lobes not present on prior imaging. A diagnostic bronchoscopy with BAL revealed 140 white-blood cells, 4 polys, 60 lymphocytes, 30 monocytes and 6 eosinophils. Flow cytometry yielded predominantly T-cells, abundant macrophages and inflammatory Infectious work up including PCP PCR, gram stain, fungal and AFB culture were negative. Ribociclib was discontinued and the patient improved symptomatically with return to baseline level of function. Reports of CDK 4/6 inhibitor drug-associated lung injury are limited There has been only one case report outside of clinical trials of Ribociclib pneumonitis.7 As these drugs become more commonly used, it is important for clinicians to be aware of this potentially fatal drug associated lung injury. Treatment with drug cessation has varying responses from recovery like in our patient to death.