Long-term response in high-grade optic glioma treated with medically induced hypothyroidism and carboplatin: A case report and review of the literature

Glioblastoma multiforme (GBM) is the most malignant and frequent brain tumor, with an aggressive growth pattern and poor prognosis despite best treatment modalities. Long-term survival of patients with GBM is rare. Optic glioma represents 0.6-1.2% of all brain tumors. Unlike low-grade optic gliomas in children, optic gliomas in adults are highly aggressive and death usually occurs in less than a year. Prolonged progression-free survival and survival rates have been reported in association with induced hypothyroidism in two clinical trials for recurrent GBM. We present the clinical, radiological, and pathological findings in a patient with inoperable GBM of the optic chiasm. Following failure of initial, standard radiation and temozolomide therapy, chemical hypothyroidism was induced using the antithyroid thioamide, propylthiouracil, followed by carboplatin chemotherapy. Initial thyroid stimulating hormone, free T4, and free T3 analysis was carried out and then monthly. This patient responded rapidly to treatment (clinically and with tumor regression within 4 weeks) on two separate occasions with an extended remission period (2.5 years) and prolonged overall survival (4.5 years). We report the successful long-term tumor response to medically induced chemical hypothyroidism in conjunction with carboplatinum chemotherapy of an adult patient with grade IV GBM of the optic chiasm. These clinical observations find mechanistic support from the recent identification of potent mitogenic actions of the thyroid hormone, L-thyroxine, in malignant glioma through binding to a cognate thyroid hormone receptor on the αvβ3 integrin. Approaches to block its activity are now explored in preclinical studies.