Overall Survival Not Affected by Childhood Radiation-Related Thyroid Cancer: Presented at ATA

By Frances Morin

WASHINGTON, DC -- October 10, 2018 -- The development of thyroid cancer as a result of childhood exposure to radiation treatment does not affect patients overall survival time, although the irradiation may play a role in the cause of death, according to a study presented here at the 88th Annual Meeting of the American Thyroid Association (ATA).

“The distribution of causes of death was different in subjects with thyroid cancer compared with controls, but there was no significant difference in the deaths caused by cancer or cardiovascular disease,” said Dan. V. Mihailescu, MD, University of Illinois College of Medicine, Chicago, Illinois.

While differentiated thyroid cancer (DTC) is the most common adverse effect of childhood irradiation, studies on the nature and survival of thyroid cancers stemming from the irradiation are lacking.

In an effort to better evaluate the overall survival and differences in the cause of death in patients with DTC from childhood irradiation, the researchers analysed data on 4,296 subjects who had been treated at Michael Reese Hospital in Chicago with external head and neck irradiation for enlarged tonsils under the age of 16, since 1974.

They identified 1,008 subjects with data on individual thyroid dose estimates available, including 353 thyroid cancer cases, and those patients were matched with 2 controls each who did not develop thyroid cancer (n = 694).

There were no significant differences in the groups in patient characteristics or thyroid dose during treatment.

At the end of the observation period (December, 2016), 168 of the 694 (24.2%) patients in the control group died, compared with 94 of the 353 (26.6%) among those who developed thyroid cancer.

The stratified survival analysis showed no significant difference in survival between those who developed DTC and those who did not (P = .92).

Furthermore, the difference in survival remained non-significant even after the elimination of papillary microcarcinomas <10 mm in size (P = .07).

While malignancies as the cause of death were similar among those who did and did not develop cancer (51% vs 48%, respectively), cardiovascular causes of death were more common in the thyroid cancer group (26% vs 16%), and other causes were less common in the thyroid cancer group (23% vs 36%).

A total of 4 patients in the entire dataset died of thyroid cancer, including 2 of metastatic disease soon after diagnosis and 2 died decades later after the initial diagnosis and many treatments.

“In a cohort of radiation-exposed individuals, development of thyroid cancer did not affect the overall survival rate,” said Dr. Mihailescu. “The difference in survival remained non-significant even after elimination of microcarcinomas.”

[Presentation title: Radiation-Induced Thyroid Cancer Does Not Affect All-Cause Survival. Abstract Oral 7]

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