In mildest cases of thyroid cancer, radioactive iodine therapy may be unnecessary

While radioactive iodine is routinely prescribed to treat many forms of thyroid cancer, a group of New York researchers stated that this therapy may be unnecessary or even dangerous for patients with the mildest forms of the disease.

Endocrinologists from the Memorial Sloan-Kettering Cancer Center recently reported that individuals who received radioactive iodine therapy (RIT) for low-risk, well-differentiated thyroid cancer had a 21 percent higher likelihood of suffering a malignant recurrence later on.

The team calculated this risk by examining data collected in the Surveillance, Epidemiology, and End Results Database of the National Cancer Institute. Between 1973 and 2007, more than 37,000 participants were diagnosed with well-differentiated thyroid carcinomas.



In all, about 14,500 of these individuals underwent RIT, roughly 3,200 of whom were subsequently diagnosed with secondary primary malignancies (SPMs).



Many of these patients originally had low-risk T1N0 thyroid cancers, a designation that ranks low on the American Joint Committee on Cancer's standardized thyroid carcinoma classification scale. "T1" indicates a tumor less than two centimeters across and "N0" means that there is no noticeable lymph node involvement.

Researchers noted that the rate of RIT for T1N0 tumors increased dramatically over the study period, from 3.3 percent in 1973 to more than 38 percent in 2007.

The thyroid gland absorbs almost all of the iodine in the blood, which is why radioactive isotopes of the element are used to specifically target and destroy cancerous thyroid cells, the American Cancer Society states. However, the introduction of radioactive material into the body is not without its own risks.

The new study, which appeared in the journal Cancer, found that RIT for T1N0 thyroid tumors was associated with a 21 percent increased likelihood of SPMs.

By contrast, the Columbia University Department of Surgery estimates that such low-risk thyroid cancers should recur in the neck at a rate of 5.5 percent, and in distant bodily sites in just 2.8 percent of cases.

Researchers concluded that RIT may be unnecessary in low-risk cases of thyroid cancer. The group emphasized that for more dangerous forms of the disease, RIT remains a viable option. 
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