A phase II study of gefitinib in patients with advanced thyroid cancer

Abstract

6020 Background: There are few effective treatments for locally advanced or metastatic thyroid cancers that are refractory to radioactive iodine (RaI). The epidermal growth factor receptor (EGFR) is highly expressed on normal and malignant thyroid tissue, and has been associated with a worse prognosis in well-differentiated thyroid cancer. The EGFR tyrosine kinase inhibitor gefitinib is effective in inhibiting the growth of thyroid cancer cells in vitro. This study sought to determine the efficacy and tolerability of gefitinib in patients with advanced thyroid cancer. Methods: In this open-label phase II trial, patients with RaI-refractory, locally advanced or metastatic thyroid cancer received 250mg of daily gefitinib. Anaplastic and medullary thyroid carcinoma were considered RaI refractory based on histology. The primary endpoint was overall response rate. Secondary endpoints were toxicity, progression-free survival (PFS), overall survival (OS), and tumor marker responses. Tumor markers consisted of serum thyroglobulin (Tg) in the differentiated cancers and serum calcitonin and carcinoembryonic antigen in medullary thyroid cancer. Results: A total of 27 patients were enrolled. 59% were male and the median age was 65. Histologic subtypes included papillary (41%), follicular (22%), anaplastic (19%), medullary (15%), and Hürthle cell carcinoma (4%). There were no objective tumor responses among the 25 patients evaluated, at which point the trial was halted. However, 32% of patients had objective reductions in tumor volume that did not meet criteria for PR. 48%, 24%, and 12% of patients had stable disease (SD) after 3, 6, and 12 months of treatment. Median PFS and OS were 3.7 [95% CI; 1.8, 5.7] and 17.5 months [9.2, not yet reached]. Five patients with SD had a decrease in Tg to <90% of baseline level that was maintained for at least 3 months. Gefitinib was well tolerated, with 11% of patients experiencing grade 3 toxicity. Conclusions: Gefitinib therapy did not result in any objective tumor responses. However, reductions in tumor volume, falling Tg levels, and prolonged SD in a subset of patients may indicate biologic activity. The OS of 17.5 months was superior to historical rates in this population. However, the significance of this is difficult to interpret in the absence of a randomized comparison group. No significant financial relationships to disclose.