Clinical outcomes of multifocal papillary thyroid cancer: A systematic review and meta-analysis.

Objective: Papillary thyroid cancer (PTC) is the most common endocrine malignancy with a steadily increasing incidence. Researches have reported that tumor multifocality occurs in an extensive number of cases. Nevertheless, the clinical characteristics and prognostic value remained controversial. This study was performed to investigate the relationship between multifocal PTC and adverse clinicopathologic features and the prognosis. Methods: A systematic review and meta-analysis were conducted based on three electronic databases up to December 31, 2021. Parameters of interest included five clinical features (extrathyroidal extension, lymphovascular invasion, central lymph node metastasis, lateral lymph node metastasis, distant metastasis) and were pooled into risk ratios (RRs). Time-to-event data (recurrence-free survival and all-cause mortality) were evaluated using hazard ratios (HRs). Publication bias was examined using funnel plots and Egger's test. Results: A total of 23 articles were included according to the inclusion criteria; all of the studies were retrospective cohorts. In comparison with unifocality, multifocality showed an increased risk of extrathyroidal extension (RR 1.38, 95% CI 1.25-1.53), lymphovascular invasion (RR 1.27, 95% CI 1.04-1.55), central lymph node metastasis (RR 1.21, 95% CI 1.12-1.30), lateral lymph node metastasis (RR 1.86, 95% CI 1.62-2.14), and distant metastasis (RR 1.35, 95% CI 1.03-1.76). Multifocal patients were predisposed to postoperative recurrence (HR 1.76, 95% CI 1.50-2.07). The rate of all-cause mortality did not reach a statistical difference. Level of Evidence: 2. Conclusion: Multifocal PTC is more aggressive in contrast to unifocal PTC and is accompanied by an increased risk of recurrence. They were usually diagnosed in higher grades and stages. To achieve the maximal benefit, we recommend personalized therapy and close follow-up for multifocal PTC patients. Further prospective studies will clarify the best-fitted treatment plans.