A narrative review of targeted therapy in meningioma, pituitary adenoma, and craniopharyngioma of the skull base

Management of solid tumors involving the skull base are primarily managed with surgery and radiation, though proximity to important vascular and neuroanatomic structures often limit the extent of resection and permissible radiation dose. Meningiomas are the most common primary brain tumor in adults, and although the majority of skull base meningiomas are low-grade, their location in proximity to critical anatomical structures precludes aggressive surgical resection, and larger tumors are often resistant to radiation treatment. In patients with clinically aggressive, unresectable meningiomas, several molecular biomarkers of angiogenesis, as well as genetic mutations (SMO, A4KT1, PIK3CA, KLF4, POLR2, SMARCE1, and TRAF7), have been shown to play a crucial role in the pathophysiology of these tumors. Pituitary adenomas are commonly slow growing tumors that are amenable to surgical resection, but tumors with higher Ki67 proliferative indices are associated with an increased risk of relapse and resistance to standard therapies. Chemotherapeutic agents and checkpoint inhibitors have been trialed, albeit with limited success, to treat these aggressive pituitary adenomas. Craniopharyngiomas are categorized as adamantinomatous and papillary subtypes, each with unique molecular mechanisms that drive pathogenesis of these tumors, and have introduced the possibility that targeted therapies may be developed for improved neurologic and endocrinological outcomes. Skull base tumors that exhibit recurrence despite surgical resection and radiation treatment pose a unique challenge, and systemic agents offer a non-invasive option of treating tumors that are refractory to conventional approaches. Recent insights into the molecular aberrations that elucidate the pathophysiology of these difficult-to-treat tumors have provided potential therapeutic targets for drug delivery. In this review, the authors discuss promising therapies and current knowledge gaps needed for the development of effective targeted agents for meningioma, pituitary adenoma, and craniopharyngioma.