CANCER INCIDENCE AND MORTALITY IN HYPERTHYROID PATIENTS TREATED SURGICALLY- A NATION-WIDE COHORT STUDY WITH LONG-TERM FOLLOW-UP

Presentation Number: OR50-5
Date of Presentation: June 18th, 2013

Saara Metso1, Essi Ryödi*2, Pia Jaatinen1, Heini Huhtala3, Rauni Saaristo2, Matti Välimäki4, Anssi Auvinen5 and Jorma Salmi2
1Tampere Univ Hosp, Tampere, Finland, 2Tampere University Hospital, Tampere, Finland, 3University of Tampre, Tampere, Finland, 4Helsinki University Hospital, Finland, 5University of Tampere, Tampere, Finland

Abstract

Background

Increased risk of cancer, especially cancer of the stomach, breast and kidney, has been observed in hyperthyroid patients treated with radioactive iodine (1-3). Currently, it is unclear whether it is the disease or the treatment that causes the increased risk of cancer. The aim of the study was to assess the impact of hyperthyroidism per se by analyzing the long term cancer risk among patients treated surgically for hyperthyroidism. Methods 

Information on cancer cases, and the date and cause of death among 4,334 patients (3719 women and 615 men) treated surgically for hyperthyroidism between January 1986 and December 2007, and 12,991 age- and gender-matched reference subjects were obtained from Hospital Discharge Registry (HILMO), The Finnish Cancer Registry and the Statistics Finland. The follow-up began three months after thyroidectomy and ended on the day of the cancer diagnosis, death, emigration from Finland, or the common closing day December 31st 2009, whichever occurred first. Results

There were 419 (9.1 %) new cancers among the patients and 1178 (9.1 %) among the controls during the follow-up. The overall cancer risk was not statistically significantly increased among the patients compared to the controls (RR 1.07, 95% CI 0.96-1.20). However, the risk of cancers of the respiratory tract (RR 1.57, 95% CI 1.04-2.36), the skin (RR 1.25, 95% CI 1.00-1.57) and the stomach (RR 2.00, 95% CI 1.06-3.77) was increased and the risk of gynecological cancer was decreased (RR 0.64, 95% CI 0.41-1.00) among the patients compared to the control group. The overall mortality for cancer was not statistically significantly increased among the patients compared to the controls (RR 1.19, 95% 0.99-1.42). Conclusions

Hyperthyroidism per se does not increase the risk of cancer. The increased risk of cancer of the respiratory tract, the skin and the stomach might be explained by the early detection caused by regular observation of the patients treated surgically. Furthermore, the increased risk might be explained by the common risk factors  associated with both cancer and hyperthyroidism, such as atrophic gastritis and smoking.

 

Nothing to Disclose: SM, ER, PJ, HH, RS, MV, AA, JS