Objectives: The incidence of thyroid cancer has dramatically increased over the last few decades, and up to 87% of patients have multifocal tumors. However, the prognostic impact of multifocality in patients with papillary thyroid carcinoma (PTC) remains unestablished and controversial.
Materials and methods: A systematic search was conducted using PubMed, SCOPUS, the Web of Science Core Collection, and the Cochrane Database of Systematic Reviews from their inception to June 30, 2020. The relevant studies compared recurrence rates or cancer-specific survival using the hazard ratio (HR) of multifocality; 26 studies of 34251 patients were identified and included.
Results: Recurrence rates for patients with multifocal disease were significantly higher than those with unifocal PTC (HR 1.81, 95% CI 1.52–2.14), while cancer-specific mortality was comparable between the groups (HR 1.19, 95% CI 0.85–1.68). In subgroup analyses, primary tumor size (HRs for PTC ≤1 cm and >1 cm were 1.81 and 1.90, respectively), number of tumor foci (HRs for two foci and more than 2 foci were 1.45 and 1.95, respectively), and patient age (HRs for pediatric and adult patients were 3.19 and 1.89, respectively) could affect the HRs of multifocality for recurrence.
Conclusions: Multifocality increases the risk of recurrence in patients with PTC. Differences in tumor size, number of tumor foci, and patient age should be considered when interpreting the impact of multifocality on the risk of recurrence.