Incidence of thyroid cancer in the Kingdom of Saudi Arabia, 2000-2010

Background: Thyroid cancer is the second most common malignancy among females at King Faisal Specialist Hospital and Research Centre (KFSH&RC) and in Saudi Arabia, accounting for about 11% of all newly diagnosed female cancers in the country in 2008. Over the past several decades, an increasing incidence of thyroid cancer has been reported in the Kingdom of Saudi Arabia. There are no comprehensive clinical epidemiological data for the trends of thyroid cancer incidence compared to the global incidence. This report reviews the thyroid cancer incidence in KFSH&RC and compares that with Saudi Arabia, the Gulf region, North America and globally from 2000 to 2010.

Methods: Retrospective review of patients with thyroid cancer was carried out from 2000 to 2010, using the hospital Tumor Registry program as per the American College of Surgeons standards. Trends and patterns of all well-known prognostic factors were sub-stratified by age, stage and grade.

Results: A total of 2292 patients with thyroid cancer were treated at KFSH&RC, Riyadh, Saudi Arabia, from 2000 to 2010. Thyroid cancer constitutes about 9% of all malignancies and 12% of all female malignancies at KFSH&RC, which are significantly higher compared to the USA, where thyroid cancer represents only 2.9% of all malignancies and 4.6% of all female malignancies. Papillary adenocarcinoma was the most common histological subtype followed by papillary carcinoma, follicular variant. Median age at diagnosis was 40 for females and 44years for males. Overall Age-Standardized Incidence Rate (ASR) was 4.4/100,000 (6.8 for female and 2/100,000 for males) in the Kingdom in 2008. Median age at diagnosis was 38years and the highest incidence was in the 30-39year age group in KFSH&RC. About 48% of patients presented in the localized stage and 60% underwent combined modality treatment consisting of surgery, radiation and hormonal therapy. There was significantly increased incidence among females as compared to males. The age-adjusted thyroid cancer incidence rates from 2000 to 2010 varied three-fold more for females than for males. Considerable geographical variations were present in thyroid cancer incidence in Saudi Arabia.

Conclusion: Thyroid cancer incidence rates have increased exponentially between 2000 and 2010 and there is significant geographical variation in the incidence of thyroid cancer throughout the Kingdom. Thyroid cancer has become the second most common cancer among young Saudi women with a male to female ratio at 0.3:1. Rising incidence of thyroid cancer in Saudi Arabia may be due to the increased detection and diagnosis of the thyroid cancers and not only an increase in the true occurrence of thyroid cancer. More studies are required to determine this significant difference at the molecular level.