Elevated liver function tests in a patient on palbociclib and fulvestrant

About 12.4% of women in the United States will be diagnosed with breast cancer at some point in their lifetime.¹ A percentage of these women will develop metastatic disease and are estimated to have a 5-year survival rate of 22%.² There have been meaningful improvements in survival because of earlier detection and more effective systemic therapies. Patients with hormone-sensitive disease often respond to endocrine therapy, and this frequently represents front-line treatment for these patients, resulting in palliation of symptoms while maintaining quality of life.

However, endocrine resistance inevitably occurs, and a great deal of research has been focused on developing strategies to combat resistance. One mechanism of endocrine resistance is though the Cyclin-dependent kinases 4 and 6 (CDK4/6) complexes. Among the most promising of the strategies to prevent resistance are the CDK4/6 inhibitors. There are now 3 approved CDK4/6 inhibitor drugs that can be used in combination with endocrine therapy, 1 of which can also be used as a single agent. When used in combination with endocrine therapy, the use of CDK 4/6 inhibitors has significantly improved progression-free survival (PFS) in patients with hormone-sensitive HER2-negative metastatic breast cancer by inhibiting cellular division and growth.³ In postmenopausal women, endocrine therapy plus CDK4/6 inhibitors are the preferred first-line regimen for metastatic disease.

Since the approval of palbociclib by the US Food and Drug Administration in 2015, the most common hematologic lab abnormalities are anemia, leukopenia, neutropenia, and thrombocytopenia. The most common nonhematologic adverse events (AEs) are fatigue, infection, nausea, and stomatitis. Hepatic toxicity has not been commonly observed. We report here the case of a 57-year-old woman on palbociclib and fulvestrant who developed significant elevation of liver function tests after starting palbociclib, suggesting a possible drug-induced liver injury from palbociclib.
 

Case presentation and summary

A 57-year-old woman with history of hypothyroidism and hypertension presented in May 2016 with a lump in her right breast and back pain. The lump was biopsied and revealed invasive ductal carcinoma, moderately differentiated, estrogen receptor (ER) positive 100%, progesterone receptor (PR) positive 95%, and HER2 negative. A positron emission tomography (PET)–computed tomography (CT) scan and magnetic resonance imaging showed bone metastasis at several vertebral levels, and the results of a bone biopsy confirmed metastatic adenocarcinoma of breast origin, ER positive 60%, PR positive 40%, and HER2 negative. No liver lesions were seen on imaging, but there was suggestion of fatty liver. She was started on letrozole 2.5 mg daily in July 2016 while undergoing kyphoplasty and subsequent radiation. A restaging PET scan revealed progression of disease on letrozole, with possible new rib lesion and progression in the breast. No liver disease was noted. Therapy was changed to fulvestrant and palbociclib. Fulvestrant was started in March 2017 with standard dosing of 500 mg intramuscular on days 1, 15, and 29, and then once a month thereafter. Her first cycle of palbociclib was started on April 5, dosed at 125 mg by mouth daily for 21 days, followed by 7 days off, repeated every 28 days (all dates hereinafter fell within 2017, unless otherwise stipulated).