Regression of a nonfunctioning pituitary macroadenoma on the CDK4/6 inhibitor palbociclib: case report

Neurosurg Focus. 2018 Jun;44(6):E9. doi: 10.3171/2018.2.FOCUS17660.


A 71-year-old female patient was referred in 2013 for evaluation of an asymptomatic nonsecreting pituitary adenoma. The adenoma, measuring 13 mm in height by 10 mm in width, was discovered incidentally on imaging in 2012. Biochemical testing demonstrated a nonfunctioning adenoma. Given the relatively small lesion size and the lack of symptoms, observation was preferred over surgical intervention. The patient was monitored with routine MRI, which until 2016 demonstrated minimal growth. In early 2016, the patient developed recurrence of metastatic breast cancer and was treated with palbociclib, a cyclin-dependent kinase (CDK) 4/6 inhibitor. This inhibitor acts on a pathway believed to be involved in pituitary adenoma tumorigenesis. One year after starting palbociclib, routine imaging demonstrated significant regression of her pituitary adenoma. The authors hypothesize that inhibition of the CDK4/6 pathway by palbociclib contributed to adenoma regression in this patient, and that palbociclib may represent a possible adjuvant therapy for the treatment of nonfunctioning pituitary adenomas.

Keywords: CDK4/6 = cyclin-dependent kinase 4 and 6 complex; CDK4/6 inhibitor; palbociclib; pituitary adenoma.

Publication types

  • Case Reports

MeSH terms

  • Adenoma / diagnostic imaging
  • Adenoma / drug therapy*
  • Aged
  • Antineoplastic Agents / pharmacology
  • Antineoplastic Agents / therapeutic use*
  • Cyclin-Dependent Kinase 4 / antagonists & inhibitors*
  • Cyclin-Dependent Kinase 6 / antagonists & inhibitors*
  • Female
  • Humans
  • Piperazines / pharmacology
  • Piperazines / therapeutic use*
  • Pituitary Neoplasms / diagnostic imaging
  • Pituitary Neoplasms / drug therapy*
  • Pyridines / pharmacology
  • Pyridines / therapeutic use*
  • Remission Induction


  • Antineoplastic Agents
  • Piperazines
  • Pyridines
  • CDK4 protein, human
  • CDK6 protein, human
  • Cyclin-Dependent Kinase 4
  • Cyclin-Dependent Kinase 6
  • palbociclib