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

• Published in: The journal of clinical endocrinology and metabolism Vol. 99; no. 8; pp. 2834 - 2843
• Main Authors: Mehanna, Hisham, Al-maqbili, Taleb, Carter, Ben, Martin, Emma, Campain, Nicholas, Watkinson, John, McCabe, Chris, Boelaert, Kristien, Franklyn, Jayne A.
• Format: Journal Article
• Language: English
• Published: Bethesda, MD Oxford University Press 01.08.2014; Copyright by The Endocrine Society; Endocrine Society
• Subjects: Adult; Biological and medical sciences; Carcinoma, Papillary - diagnosis; Carcinoma, Papillary - mortality; Carcinoma, Papillary - therapy; Data collection; Endocrinopathies; Feeding. Feeding behavior; Female; Follow-Up Studies; Fundamental and applied biological sciences. Psychology; Humans; Incidental Findings; Lymph nodes; Male; Malignant tumors; Medical sciences; Meta-analysis; Middle Aged; Papillary thyroid cancer; Prognosis; Recurrence; Risk Factors; Survival Analysis; Thyroid gland; Thyroid Neoplasms - diagnosis; Thyroid Neoplasms - mortality; Thyroid Neoplasms - therapy; Thyroid. Thyroid axis (diseases); Tumors; Vertebrates: anatomy and physiology, studies on body, several organs or systems; Vertebrates: endocrinology; Endocrinopathy; Obesity; Relapse; Prognosis; Nutrition; Mortality; Rate; Thyroid diseases; Nutrition disorder; Metabolic diseases; Systematic review; Malignant tumor; Epidemiology; Thyroid carcinoma; Metaanalysis; Surveillance; Evolution; Endocrinology; Nutritional status; Comparative study; Cancer
• ISSN: 0021-972X; 1945-7197; 1945-7197
• DOI: 10.1210/jc.2013-2118

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:Two reviewers 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 abstracts and articles, extracted data, and assessed 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, 6.9 mm [range 5.6–8.0 mm]). The recurrence rate in the incidental group (0.5%; 95% confidence interval [CI], 0–1%, P < .001) was significantly lower than that in the nonincidental group PTMC (7.9%; 95% CI, 5–11%), with an OR of recurrence of 14.7 (95% CI, 5.6–54.8, P < .001) for nonincidental PTMC, compared with incidental PTMC. Lymph nodes were involved in 80% (126/157) of recurrences. On meta-regression, age, sex, size, tumor multifocality, lymph node involvement, and treatment modality were not significantly associated with recurrence.Conclusions:Our meta-analysis strongly suggests the existence of at least two distinct entities of PTMC. Incidental PTMC has different clinical characteristics and a much lower recurrence rate than nonincidental PTMC, suggesting that management protocols should be re-considered. Additional studies with standardized data collection are required to explore potential differences between subgroups of nonincidental PTMC.