Differences in the recurrence and mortality outcomes rates of incidental and nonincidental papillary thyroid microcarcinoma: A systematic review and meta-analysis of 21 329 person-years of follow-up

Abstract

Context: There is controversy as to whether papillary thyroid microcarcinoma (PTMC) represents more than one disease entity with different outcomes, requiring different treatment. Objectives: To compare characteristics, outcomes, and factors associated with prognosis of incidental and nonincidental PTMC. Setting and Design:Tworeviewers performed searches of online databases (1966-2012), reference lists, and conference abstract books. Longitudinal studies of subjects >16 years old receiving any treatments for papillary thyroid cancer ≤10 mm in size were included. Two reviewers independently screened abstractsandarticles, extracted data,andassessed quality of studies using National Institute of Clinical Excellence and PRISMA criteria. Results: Of 1102 abstracts identified, 262 studies were reviewed and 17 studies included, comprising 3523 subjects, with mean follow-up of 70 months and total follow-up of 21 329 person-years. This included 854 subjects with incidental PTMC (follow-up, 4800 person-years; mean tumor size, 4.6 mm [range 3.3- 6.7 mm]) and 2669 nonincidental PTMC cases (follow-up, 16 529 person-years; mean tumor size, 6.9mm[range 5.6-8.0 mm]). The recurrence rate in the incidental group (0.5%; 95%confidence interval [CI], 0-1%, P