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Clin Endocrinol (Oxf). 2015 Jul;83(1):117-23. doi: 10.1111/cen.12581. Epub 2014 Oct 10.

The risk of second primary malignancy is increased in differentiated thyroid cancer patients with a cumulative (131)I dose over 37 GBq.

Author information

1
Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea.
2
Department of Internal Medicine, National Medical Center, Seoul, Korea.
3
Department of Internal Medicine, Chung-Ang University Hospital, Seoul, Korea.
4
Department of Internal Medicine, Dankook University Hospital, Cheonan-si, Korea.
5
Department of Nuclear Medicine, Seoul National University College of Medicine, Seoul, Korea.
6
Department of Internal Medicine, Seoul National University Boramae Medical Center, Seoul, Korea.
7
Department of Laboratory Medicine, Seoul National University College of Medicine, Seoul, Korea.

Abstract

BACKGROUND:

The aim of this study was to investigate the risk factors for second primary malignancy (SPM) diagnosed after differentiated thyroid cancer (DTC).

METHODS:

A total of 2468 DTC patients who underwent thyroidectomy were reviewed. SPM was defined as a non-thyroidal malignancy, diagnosed at least 1 year after the diagnosis of thyroid cancer. Patients were divided into five groups according to cumulative (131)I dose: very high-activity (≥ 37.0 GBq), high-activity (22.3-36.9 GBq), intermediate-activity (5.56-22.2 GBq), low-activity (1.1-5.55 GBq) and no RAI.

RESULTS:

Among the 2468 patients, 61 (2.5%) had SPMs during 7.0 (1.0-33.0) years of median follow-up. Age above 40 years, male sex and very high-activity RAI were independent risk factors for the development of SPM. SPM-related mortality was highest in the very high-activity group, while DTC-related mortality was highest in the high-activity group. The overall mortality both from SPM and DTC was highest in the high-activity group.

CONCLUSION:

A cumulative (131)I dose <37.0 GBq did not increase the risk of SPM. A cumulative (131) I dose ≥ 37.0 GBq increased the risk of SPM and SPM-related mortality and decreased the DTC-specific mortality, resulting in a similar all-cause mortality compared with the low-activity RAI group. Using repeated high-dose RAI for treating RAI-responsive but persistent DTC patients needs careful consideration of the individual benefits from RAI vs the risk of developing SPM.

PMID:
25115234
DOI:
10.1111/cen.12581
[Indexed for MEDLINE]

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