A UK based two-centre review of multifocality and its role in the treatment of papillary thyroid cancer

Introduction Multifocality is increasingly observed in papillary thyroid carcinoma (PTC) due to improvements in imaging and histopathological analysis. However, its significance in management, particularly as a sole risk-factor, remains controversial. This study aimed to investigate the prognostic value of multifocality in predicting recurrence following thyroid lobectomy in a contemporary group of PTC patients managed in the UK. Methods Patients with PTC in NHS Lothian (2009-19) and Guys and St Thomas NHS Foundation Trust (2012-19) were identified. Categorical variables were compared using Chi-squared or Fisher’s exact test. Five-year recurrence free survival (RFS) were analysed using Kaplan-Meier method and compared using log-rank. Results Of 828 patients; 492 (59%) had unifocal and 336 (41%) multifocal disease on final pathology. A higher rate of pathological nodal disease (22%v36%,p<0.001), total thyroidectomy (TT) (78%v92%,p<0.001) and radioactive iodine (RAI) (57%v75%,p<0.001) was demonstrated in patients with multifocality. With a median follow-up of 50 months, overall 5-year RFS was 96.5%; 96.5% for unifocal versus 96.6% for multifocal disease (p=0.695). Recurrence was not shown to be associated with multifocality on either univariate or multivariate analysis. Amongst patients with T1/2N0M0 disease (n=341), more patients were treated with TT and RAI with multifocal compared to unifocal disease (<0.001). Only two patients within this group recurred during follow up, both of whom had multifocal disease and were treated with TT and RAI (5yRFS100%v98.1%,p=0.051). Conclusion Multifocality is a common feature of PTC but does not appear to be an independent predictor of outcome. Therefore, treatment intensification on the basis of multifocality alone seems unwarranted.