Disease progression
We considered two main factors affecting the tumor growth rate and the recurrence rate:
(1) Patient age 16: The growth rate of the primary tumor was estimated to be 0.0091 (range 0.0082-0.01) for patients aged 40-59 years old and 0.004 (range 0.0036-0.0044) for patients more than 60 years old. The rate of locoregional progression during AS was 0.0023 (range 0.0021-0.0025) and 0.0005 (range 0.00045-0.00055) for patients aged 40–59 years and more than 60 years old respectively. The recurrence rate after HT was estimated to be 0.004 (range 0.003-0.005) independent from age.14
(2) BRAFV600Estatus 10: To calculate the recurrence rate following HT in patients with lrPTMC who are positive toBRAFV600E mutation we used the Kaplan-Meier curves for disease recurrence-free survival for a patient with low-risk conventional PTMC and BRAFV600E as presented by Kim et al.10 We digitized the curves using GetData Software and fit the data to an exponential distribution, estimating the recurrence rate of BRAFV600E mutation-positive and BRAFV600E mutation-negative, respectively. We then calculated the hazard ratio (HR) of recurrence-free survival between the BRAFV600E mutation-positive andBRAFV600E mutation-negative patients. We assumed the same HR also for the tumor growth rate and the rate of progression to loco-regional disease. Lastly, we assumed that the patient BRAFV600E status is known.