Estimation of the lifetime probability of disease progression of papillary microcarcinoma of the thyroid during active surveillance

Background. We reported that a minority of patients with low-risk papillary microcarcinoma of the thyroid showed disease progression during active surveillance and that older patients had significantly lower disease progression rates than younger patients. Here, we estimated lifetime (<= 85 years old) probabilities of disease progression during active surveillance according to the age at presentation based on age decade-specific disease progression rates. Methods. From 1993-2013, 1,211 low-risk papillary microcarcinoma patients aged 20-79 years underwent active surveillance at Kuma Hospital. We calculated the disease progression rate at the 10-year point of active surveillance for each age-decade group (20s to 70s) with the Kaplan-Meier method. The lifetime disease progression probability for each age group was calculated as (1 - cumulative probability of progression-free survival calculated with age decade-specific disease progression rates) until the patients reached their 80s (i.e., 85 years on average). Results. The age decade-specific disease progression rates at 10 years of active surveillance were 36.9% (20s), 13.5% (30s), 14.5% (40s), 5.6% (50s), 6.6% (60s), and 3.5% (70s); the respective lifetime disease progression probabilities were 60.3%, 37.1%, 27.3%, 14.9%, 9.9% and 3.5% according to the age at presentation. Conclusion. The estimated lifetime disease progression probabilities of papillary microcarcinoma during active surveillance vary greatly according to the age at presentation. (C) 2017 The Author(s). Published by Elsevier Inc.