Introduction: Pituitary adenomas account for up to 15% of intracranial masses with the most common subtypes being prolactinomas and non-functioning pituitary adenomas (NFPA). The gold standard of treatment for prolactinomas is anti-dopaminergic medication while for non-functioning pituitary adenomas it is surgical resection. Though surgical resection is the mainstay of treatment for NFPAs at this time, there are several known pathways involved in NFPA tumorigenesis and, thus, targeted medical therapy may prove to be a valid treatment modality for NFPAs.
Methods: This principal is exemplified in the case of a 71-year-old woman who was referred for evaluation of an asymptomatic non-secreting pituitary adenoma. The adenoma measured 9 mm in height x 10 mm in width x 9 mm in AP diameter on MRI imaging in 2008. The patient was followed with serial MRIs. In March of 2016, the tumor was found to have increased in size to 14mm x 16mm x 9mm in the same dimensions (Figure 1). No treatment for her enlarging pituitary adenoma was recommended because she had recently developed recurrent metastatic breast cancer.
Results: She was treated for her recurrence of breast cancer 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. Now, after two years of palbociclib treatment, her tumor continues to regress and measures 8mm x 10mm x 8.5mm (Figure 2).
Conclusions: We hypothesize that inhibition of the CDK 4/6 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. Furthermore, we postulate that there are other well-known pathways involved in NFPA tumorigenesis that may represent potential therapeutic targets.
Patient Care: Surgical resection is currently the gold standard of treatment for non-functioning pituitary adenomas. Our research proposes that medical therapy may be a valid treatment for non-functioning pituitary adenomas, thus, providing patients with a less invasive form of treatment and eliminating risks of surgical intervention. Additionally, targeted medical therapy may be useful as an adjuvant therapy to surgery with the resulting tumor regression enabling improved resection and subsequently preventing tumor recurrence.
Learning Objectives: By the conclusion of this session, participants should be able to 1) Understand why palbociclib may be an effective treatment modality for non-functioning pituitary adenomas 2) Identify potential therapeutic targets within other well-known pathways involved in NFPA tumorigenesis 3) Recognize the utility of medical therapy in the treatment of non-functioning pituitary adenomas.