Are Newly Treated Thyroid-Cancer Patients Hazardous to Our Health?

BY MATTHEW D. RINGEL, MD, professor of Medicine in the Division of Endocrinology, Diabetes and Metabolism, with joint appointments in the Division of Medical Oncology and the Department of Molecular Virology, Immunology and Medical Genetics. In 2009, he was awarded the American Thyroid Association’s Van Meter Award, which is presented to an investigator age 45 or under who has made outstanding contributions to thyroid disease research.

Matthew RingelThis autumn the question again arose in the media about whether thyroid-cancer patients just treated with a radioactive isotope of iodine pose a hazard to those around them. Should those individuals be quarantined before returning home following treatment? While this hazard may be theoretical, it is worth recalling that many members of the public have a limited understanding of radiation and an almost instinctive fear of radioactivity at any level. Our post-911 world involves closer monitoring of low-level radioactivity at airports, landfills and tunnels, giving the question added life.

More than 44,000 new cases of thyroid cancer are expected to occur in Americans this year. Most of those individuals will be treated with I-131, a radioactive isotope of iodine that concentrates in the thyroid gland and destroys cancer cells. I-131 has been used for decades to treat thyroid cancer. Here at Ohio State, a major thyroid cancer referral center, we treat a large number of thyroid cancer patients, many of whom receive I-131 therapy during their management.

In 1997, the Nuclear Regulatory Commission (NRC) relaxed its guidelines governing the therapeutic use of I-131 to allow more patients to return home following therapy instead of quarantining them in the hospital. The change was made after studies concluded that most patients treated with I-131 posed little risk to their families and others when patient doses and physical characteristics result in low exposure levels, and when simple and reasonable measures are followed after patients leave the clinic.

I-131 has a half-life of about eight days and is flushed from the body in the urine and the gastrointestinal tract. Thus, through both radioactive decay and excretion, the I-131 that is not taken up by the thyroid cells is quickly cleared from the body.

Patients treated for thyroid cancer at The Ohio State University Comprehensive Cancer Center – Arthur G. James Cancer Hospital and Richard J. Solove Research Institute are released in strict accordance with Ohio Department of Health regulations and in accordance with NRC guidelines. All patients receive detailed verbal and written instructions prior to treatment describing how to maximize the clearance of the I-131 and how to minimize exposure to those in their homes. This education process begins in the treating clinician’s office and continues with our thyroid cancer nurses after the visit, with our nuclear medicine physicians and with their radiation safety officers. Importantly, if the exposure exceeds 500 millirems, or if patients are unable to follow the recommendations for safe discharge home, they are admitted to the hospital until safe exposure levels are achieved.

These practices are the current standard of care and are endorsed by the American Thyroid Association, The Endocrine Society, the Society of Nuclear Medicine, and the American Association of Clinical Endocrinologists. Per an October 20, 2010, joint statement from these organizations, “The American Thyroid Association has recently completed an examination of the current scientific evidence for any potential risks to the public from I-131 therapy of thyroid cancer. It is anticipated that the report will provide updated recommendations for best practices focusing on patient and public safety following I-131 treatment.”

Our goal at Ohio State is to treat all patients using evidence-based best practices. For patients with thyroid cancer, this often includes I-131 therapy. We are committed to using this treatment in a manner that is safe for patients, their families and the public. We believe this is best afforded by following current NRC and society-approved recommendations and guidelines, which include careful attention to administered dose, detailed patient education and instructions, and open communication between physicians and patients.

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