NEW YORK (Reuters Health) – A study of Chernobyl survivors shows no difference in recurrence patterns between radiation-related and sporadic thyroid cancers.

“Similar treatment approaches should be recommended for both nonexposed patients and for those exposed to internal radiation,” the research team advises.

It’s well known that with radiation exposure, the risk of thyroid cancer is proportional to the dose and that it remains elevated for decades, according to lead author Dr. Pavel Rumyantsev of the Russian Academy of Medical Sciences in Obninsk and colleagues.

Not surprisingly, people exposed to radioactive fallout from the 1986 Chernobyl nuclear plant accident have had high rates of thyroid cancer, and in particular, papillary carcinoma, which has an aggressive course and a high recurrence rate. But most studies have not considered whether that recurrence rate is affected by radiation, the authors say.

So in a retrospective analysis, reported online November 17 in the Journal of Clinical Endocrinology and Metabolism, the research team compared 172 Chernobyl survivors with papillary thyroid carcinoma (PTC) to 325 patients with sporadic PTC matched for age, sex and time to treatment. All were under the age of 18 in 1986.

During follow-up between 1991 and 2008, 25 Chernobyl PTC patients and 64 sporadic PTC patients developed recurrent disease (14.5% vs. 19.7%; p=0.177).

The risk of recurrence was increased by the presence of regional metastases (hazard ratio 5.21; p=0.0053), and it was reduced by the presence of a tumor capsule (HR, 0.17; p=0.0003) or treatment that followed American Thyroid Association management guidelines (HR, 0.16; p=0.0002).

The researchers say none of the factors that significantly affected recurrence resulted in higher recurrence rates in the radioiodine-exposed patients.

“It is necessary to emphasize that none of the potential risk factors tested was specific to the radiation-related or sporadic PTC group,” the researchers wrote.

“PTC developing after internal exposure to radioiodine does not display specific risk factors for recurrence different from those in sporadic PTC,” they conclude. “Common treatment approaches…should be recommended regardless of a history of radiation exposure.”

Reference:

Radiation Exposure Does Not Significantly Contribute to the Risk of Recurrence of Chernobyl Thyroid Cancer

J Clin Endocrinol Metab 2010.