Papillary thyroid microcarcinoma: an over-treated malignancy?

The clinical importance of papillary thyroid microcarcinoma (PTMC) remains controversial, with current guidelines suggesting that thyroid lobectomy alone is sufficient. The purpose of this study was to identify population-level treatment patterns in the USA for PTMC.

Patients with PTMC in SEER (1998-2010) were included; demographic, clinical (extent of surgery, administration of post-operative radioactive iodine [RAI]), and pathologic characteristics were examined. Outcomes of interest were 5- and 10-year overall survival (OS) and disease-specific survival (DSS).

The cohort consisted of 29,512 patients. Mean age at diagnosis was 48.5 years; mean tumor size was 0.53 cm. Overall, 73.4 % of patients underwent total thyroidectomy, and RAI was administered to 31.3 %. In multivariate analysis, total thyroidectomy was more frequently performed in patients with multifocal (odds ratio [OR] 2.55), 'regional', or 'distant' PTMC (OR 2.90 and 2.59). Non-operative management was associated with male patients (OR 4.24) and those aged ≥65 years (OR 6.31). Post-operative RAI was associated with multifocal PTMC (OR 2.57). Overall, 5- and 10-year DSS was 99.6 and 99.3 %, respectively, with no difference in DSS between patients who underwent partial versus total thyroidectomy. OS of patients with PTMC who underwent any thyroid operation was similar to that of the general population of the USA.

An increasing number of patients are undergoing total thyroidectomy and RAI for PTMC. While there may be a subset of patients for whom more aggressive therapy is indicated, many patients with PTMC may be over-treated, with no demonstrable benefit to survival.