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.