Natural history of papillary thyroid microcarcinoma: Kinetic analyses on tumor volume during active surveillance and before presentation

Background: We report on the growth of papillary microcarcinoma during active surveillance and before clinical presentation. Methods: We conducted a retrospective study of 169 patients with papillary microcarcinoma who were enrolled in active surveillance at our hospital between 2000 and 2004. Patients were followed for a median of 10.1 years using serial ultrasonography (median, 12 examinations), used to calculate the tumor doubling time. To contextualize tumor growth rates during active surveillance, we calculated the hypothetical tumor doubling time before clinical presentation. To resolve the limitations in tumor doubling time, tumor doubling rates were inversely transformed into doubling rates. Results: The doubling rates (per year) during active surveillance (median: 0.0) were >0.5, 0.1 to 0.5, -0.1 to 0.1, and <-0.1 in 5, 38, 97, and 29 cases, respectively. The proportions of tumors with rather rapid growth, slow growth, stable, and a decrease in size were 3%, 22%, 57%, and 17%, respectively. Conclusion: Tumor growth of papillary microcarcinomas varies from rather rapid growth to a decrease in size during active surveillance. (C) 2018 The Author(s). Published by Elsevier Inc.