Metformin Hydrochloride in Mitigating Side Effects of Radioactive Iodine Treatment in Patients with Differentiated Thyroid Cancer

Inclusion Criteria

• Subjects with a diagnosis of differentiated thyroid cancer who have undergone total or near-total thyroidectomy and are candidates for iodine I-131 (I-131) treatment at Thomas Jefferson University Hospital (TJUH) are eligible to participate
• Subjects must be diagnosed with differentiated thyroid cancer
• Patients must have previously undergone or plan to undergo thyroidectomy; for those patients who have previously undergone surgery, pre-operative labs, including complete blood cell count with differential must be available
• Patients who have a negative urine pregnancy test prior to enrollment; this should be done as part of pre-admission testing prior to surgery (within 14 days of study enrollment)
• All subjects must be able to comprehend and sign a written informed consent document

Exclusion Criteria

• Subjects who are pregnant or may become pregnant during metformin administration in accordance with radioactive iodine treatment guidelines
• Subjects on metformin for any reason during the preceding 4 weeks
• Diabetic subjects are eligible if they are not taking metformin, insulin or sulfonylureas
• Subjects who have received iodinated contrast dye; metformin treatment can be started the day after subjects complete iodinated contrast treatment; if a computed tomography (CT) scan with contrast is scheduled after screening and consent, the metformin treatment should be stopped the day before iodinated contrast administration; metformin can be resumed on the day after last iodinated contrast was administered to the subject
• Patients with history of hepatic dysfunction or hepatic disease and abnormal liver function tests (previously documented alanine aminotransferase greater than 40 IU/dL and/or plasma aspartate aminotransferase greater than 45 IU/d); patients who have a history of hepatic dysfunction or hepatic disease but whose most recent liver function tests have been documented as normal will be eligible to participate
• Patients with plasma creatinine level greater than 1.3 mg/dL
• Patients with plasma alkaline phosphatase greater than 190 IU/dL
• Patients with plasma bicarbonate less than 22 mEq/L or history of lactic or any other metabolic acidosis
• Patients with history of congestive heart failure
• Patients with myocardial ischemia or peripheral muscle ischemia
• Patients with sepsis or severe infection
• Patients with history of lung disease currently requiring any pharmacologic or supplemental oxygen treatment
• Patients with a current history (in the past 30 days) of heavy drinking which is defined in accordance with Centers for Disease Control and Prevention (CDC) definition as more than 8 drinks per week for women and more than 15 drinks per week for men; a standard drink contains .6 ounces of pure alcohol; generally, this amount of pure alcohol is found in 12-ounces of beer, 8-ounces of malt liquor, 5-ounces of wine, 1.5-ounces or a “shot” of 80-proof distilled spirits or liquor (e.g., gin, rum, vodka, or whiskey); while on study, patients should limit their alcohol consumption to no more than 8 drinks per week for women and no more than 15 drinks per week for men; patients who feel they cannot comply with this recommendation are not eligible
• Patients with a systemic disease that could affect their bone marrow or peripheral blood cells (e.g. systemic lupus erythematosus, human immunodeficiency virus infection, rheumatoid arthritis)
• Patients who have received or will receive medication that could affect their hematologic state (tyrosine kinase inhibitors, cytotoxic chemotherapy)
• Patients who have received previous treatment with ionizing radiation
• Patients who are non-English speaking
• All medications other than those that may cause myelosuppression are permitted except those that are contraindicated with metformin under current Food and Drug Administration (FDA) recommendations; it is important to note that the medications that are contraindicated with metformin are contraindicated due to concern for theoretical interactions