Gefitinib in Treating Patients With Locally Advanced or Metastatic Thyroid Cancer That Did Not Respond to Iodine Therapy

Inclusion Criteria: 1. Histologically or cytologically confirmed thyroid cancer, metastatic or locally advanced, not amenable or refractory to local therapy and/or radioactive iodine, depending on the cell type. 2. Thyroid cancer that is unresponsive or refractory to radioactive iodine. All medullary and anaplastic thyroid carcinomas will be considered unresponsive on the basis of histopathologic diagnosis alone. Well-differentiated thyroid cancers (papillary and follicular) will be considered refractory if either there is no evidence of uptake on radioactive iodine scanning or tumor growth persists in spite of treatment with radioactive iodine. 3. Measurable disease. 4. Patient is at least 18 years of age. 5. Eastern Cooperative Oncology Group performance status of 0-2. 6. If female and of reproductive potential, a negative β-HCG (human chorionic gonadotropin) and use of effective birth control for the course of the study. 7. Patient is capable of providing signed, informed consent. Exclusion Criteria: 1. Concurrent chemotherapy, concurrent systemic anticancer treatment, or concurrent radiation therapy. Patients will not be excluded from the study on the basis of prior radiation therapy. 2. Treatment with a non-approved or investigational drug within 30 days before Day 1 of trial treatment. 3. Currently pregnant or nursing. 4. Absolute neutrophil count \<1.5 × 109/L, platelet count \< 75 × 109/L, bilirubin \> 1.5 × normal, alanine aminotransferase (ALT) or aspartate aminotransferase (AST) \> 3 × normal. 5. Serum creatinine greater than Common Toxicity Criteria (CTC) grade 2. 6. Concomitant use of phenytoin, carbamazepine, barbiturates, rifampin, St John's Wort. 7. Concomitant use of systemic retinoids, cyclosporine, verapamil, diltiazem, nicardipine, nifedipine, nitrendipine, erythromycin, theophylline, ketoconazole, itraconazole, and antihistamines such as terfenadine and astemizole. 8. Any unresolved chronic toxicity greater than CTC grade 2 from previous anticancer therapy. 9. Incomplete healing from previous oncologic or other major surgery. 10. Known severe hypersensitivity to ZD1839 or any of the excipients of this product. 11. As judged by the investigator, any evidence of severe or uncontrolled systemic disease (e.g., unstable or uncompensated respiratory, cardiac, hepatic, or renal disease). 12. Evidence of any other significant clinical disorder or laboratory finding that makes it undesirable for the subject to participate in the trial. 13. Any evidence of clinically active interstitial lung disease (patients with chronic stable radiographic changes who are asymptomatic need not be excluded)