OBJECTIVES: I. Determine the ability of azacitidine to restore iodine uptake by dedifferentiated thyroid cancer, enabling detection and treatment with iodine I 131 in patients with metastatic follicular or papillary thyroid cancer. II. Evaluate different doses and schedules of azacitidine administration to determine an optimally effective combination for restoration of iodine I 131 uptake with acceptable toxicity in this patient population. III. Determine the efficacy of azacitidine plus iodine I 131 in this patient population.