Thyroid Research Thyroid Research Archive Thyroid Cancer

Patients with thyroid cancer have a slightly increased risk of other cancers

(July 2006)

The background of the study. Patients with one cancer may have an increased risk of another cancer. In this study, the risk of a second cancer in patients with thyroid cancer and, conversely, the risk of thyroid cancer in patients with a nonthyroid cancer were studied.

How the study was done. Data on primary cancers, including the patient’s age and sex, date of diagnosis of the first cancer and follow-up data, and date of diagnosis of the second cancer were obtained from cancer registries in 11 countries. The observed number of cancers was compared with the expected number calculated from the age-, sex-, and calendar year–specific incidence rates for each registry.

The results of the study. There were 39,002 patients with thyroid cancer, followed for 356,035 person-years; they included 29,030 women (74 percent) and 9972 men (26 percent). The thyroid cancer was a papillary carcinoma in 15,523 (40 percent), a follicular carcinoma in 5260 (13 percent), a medullary carcinoma in 1170 (3 percent), and unclassified in 17,049 (44 percent).

Among the 39,002 patients with thyroid cancer, 2821 (7 percent) had a second primary cancer of some other organ, very slightly more than expected. There were 1990 patients in whom thyroid cancer was the second cancer, also very slightly more than expected.

The conclusions of the study. The frequency of a second nonthyroid cancer is very slightly increased in patients with thyroid cancer, and, conversely, the frequency of thyroid cancer is very slightly increased in patients with other cancers.

The original article. Sandeep TC, Strachan MW, Reynolds RM, Brewster DH, Scelo G, Pukkala E, Hemminki K, Anderson A, Tracey E, Friis S, McBride ML Kee-Seng C, Pompe-Kirn V, Kliewer EV, Tonita JM, Jonasson JG, Martos C, Boffeta P, Brennan P. Second primary cancers in thyroid cancer patients: a multinational record linkage study. J Clin Endocrinol Metab 2006;91:1819-25.