Irinotecan in Treating Patients With Metastatic or Inoperable Thyroid Cancer

Inclusion * Histologically confirmed medullary thyroid cancer * Metastatic or inoperable locoregional disease * Measurable disease by CT scan * 18 years and over * ECOG PS 0-1 Adequate lab functions including: * Granulocyte count \> 1,000/mm\^3 * Platelet count \> 100,000/mm\^3 * Bilirubin \< 1.5 mg/dL * ALT and AST \< 2.5 times upper limit of normal * No unstable or uncompensated hepatic disease * Creatinine clearance \> 60 mL/min * No unstable or uncompensated renal disease * Negative pregnancy test * More than 3 months since prior biologic therapy * More than 3 months since prior chemotherapy * No prior radiotherapy to \> 25% of bone marrow * More than 3 months since prior radiotherapy * Recovered from prior oncologic or other major surgery * More than 30 days since prior non-approved or investigational drugs Exclusion: * Patients with elevated calcitonin levels as the only measurement of disease are not eligible * Unstable or uncompensated cardiovascular disease * Unstable or uncompensated respiratory disease * Pregnant or nursing * Diarrhea ≥ grade 2 (antidiarrheals allowed) * Other severe or uncontrolled systemic disease * Other malignancy within the past 5 years except squamous cell or basal cell skin cancer or cervical cancer * Illness that would preclude study participation * Significant clinical disorder or laboratory finding that would preclude study participation