Prevalence and treatment outcomes of second primary malignancies in Saudi patients with differentiated thyroid cancers

OBJECTIVES: To evaluate the clinicopathologic features, and explore the treatment outcomes of synchronous, or metachronous second primary malignancies (SPM) in conjunction with differentiated thyroid cancers (DTC). METHODS: This retrospective study was conducted on 823 DTC patients treated between 2000 and 2012 at 2 tertiary care hospitals (King Fahad Medical City and King Khalid University Hospital) in Riyadh, Kingdom of Saudi Arabia. Forty-one (5%) DTC patients were found to have SPM (61% metachronous and 39% synchronous). These patients with SPM were studied for clinicopathological features and treatment outcomes. RESULTS: The patients with DTC and SPM were older (median age: 54.3 years) than those without SPM (median age: 43.2 years); p=0.04. The frequency of SPM was breast (51.2%), colon (12.2%), kidney (7.3%), astrocytoma (7.3%), parotid (7.3%), rectum (4.9%), lymphoma (4.9%), nasopharynx (2.4%), and stomach (2.4%). Median follow-up was 8.05 years. Ten-year disease free survival, and overall survival (OS) rates were lower in DTC patients with SPM (56.1% for 10-year survival, and 71.7% for OS) than without SPM (95.5% for 10-year survival, and 97.8% for OS); p=0.0001. Metachronous SPM had better 10-year disease free survival rates (60.2%) than synchronous SPM (45%). CONCLUSION: The co-occurrence of SPM with DTC affects long-term disease free survival and OS rates.