Endocrine Abstracts

Background and Aim: The incidence of papillary thyroid microcarcinoma (mPTC) has dramatically increased in the last decades. The majority of these tumors remain small and clinically silent, only small number progress. Clinical practice guidelines currently suggest avoiding the cytological examination of subcentimeter nodules and reducing surgeries for mPTC. Several risk factors have been identified as strongly associated with a high-risk phenotype for mPTCs (e.g. gross nodal metastasis, extranodal extension). This study aims to evaluate the prevalence, the risk of recurrence and the management of mPTCs in different Italian thyroid clinical centers.

Methods: The Italian Thyroid Cancer Observatory (ITCO) was established in 2013 to collect prospective data on thyroid cancers consecutively diagnosed in member centers. We collected data of all histologically confirmed mPTCs present in the database at the end of December 2019. The risk stratification was classified according to the 2015 ATA guidelines after surgery and it was re-classified after radioiodine treatment.

Results: A total of 7747 patients, enrolled by 48 centers were included in the initial cohort. Overall, 3172 cases were mPTCs (40.9%). No significant difference in the prevalence of mPTC was detected over time. The initial risk stratification (after surgery) included: 2115 (66.7%) low-risk PTCs, 989 (31.2%) intermediate-risk mPTCs and 68 (2.1%) high-risk mPTCs. 991 patients (31.2%) underwent radioiodine treatment. Among these, the initial (after surgery) risk stratification was as follows: 385 (38.8%) low-risk PTCs, 550 (55.5%) intermediate-risk mPTCs and 56 (5.7%) high-risk mPTCs. After radioiodine treatment, the risk stratification was re-classified as follows: 360 (36.3%) low-risk PTCs, 522 (52.7%) intermediate-risk mPTCs and 109 (11%) high-risk mPTCs.

Conclusions: Despite the efforts to reduce the number of surgeries for mPTCs, these interventions are still very common. The optimal management of low-risk microPTC represents a major clinical issue. Furthermore, in recent years, in spite of the updated guidelines and scientific literature data, no relevant differences were measured in real-world clinical practice in Italy. In this large and contemporary cohort of patients, radioiodine treatment allows us to re-classify risk stratification for about 5% of mPTC patients.