Propylthiouracil-induced chemical hypothyroidism with high-dose tamoxifen prolongs survival in recurrent high grade glioma: A phase I/II study

Background: High-dose tamoxifen has had disappointing results as a palliative therapy in recurrent glioma. Insulin-like growth factor 1 (IGF-1) is a thyroid hormone modulated naturally occurring antagonist of tamoxifen-induced cytotoxicity. Thyroid function was suppressed to reduce IGF-1 levels in glioma patients and high-dose tamoxifen administered. Materials and Methods: Propylthiouracil was used to induce chemical hypothyroidism in 22 patients with recurrent glioma. Tamoxifen was started within one month and given in escalating doses from 40 mg twice a day up to 80 mg 3 times a day. No significant toxicity developed. Results: Eleven out of 22 patients became hypothyroid. No patients experienced symptoms of clinical hypothyroidism. Median survival was significantly longer in the hypothyroid group (10. 1 months versus 3.1 months); p = 0.03. There was a significant decrease in blood levels of IGF-1 (p=0.02). in hypothyroid patients. Conclusion: Patients treated for recurrent high-grade gliomas with high-dose tamoxifen had significantly longer survival when chemical hypothyroidism was induced with propylthiouracil.