An Efficacy Study Comparing ZD6474 to Placebo in Medullary Thyroid Cancer

Inclusion Criteria: * Confirmed diagnosis of unresectable, locally advanced or metastatic hereditary or sporadic Medullary Thyroid Cancer. * Presence of measurable tumor * Able to swallow medication Exclusion Criteria: * Major surgery within 4 weeks before randomization * Last dose of prior chemotherapy received less than 4 weeks prior to randomization * Radiation therapy within the last 4 weeks prior to randomization(with exception of palliative radiotherapy) * Brain metastases or spinal cord compression, unless treated at least 4 weeks before first dose and stable without steroid treatment for 10 days * Significant cardiac events * Previous ZD6474 treatment