ESPE Abstracts

Background: Childhood onset PTC has a more aggressive presentation but no overall increase in mortality compared to adults.

Objective: To characterize a pediatric cohort with PTC at diagnosis using the American Thyroid Association (ATA) Initial Risk Stratification (IRS) and to evaluate the response to initial treatment until 3 years based on the modified ATA Dynamic Risk Stratification (DRS) for adults.

Patients and Methodso: Of a total cohort of 51 patients with PTC followed at our Institution between 2008 and 2019, 31 patients with complete data and a minimum follow-up of 3 years were included in this retrospective study. Clinicopathological data and outcomes were analyzed. Until 2015 patients were treated initially with total thyroidectomy and radioiodine ablation, while after 2015 following ATA Guidelines, low risk patients were excepted from radioiodine. IRS was classified in low(L), intermediate(I) and high(H) risk according to ATA Guidelines. Clinical outcome was assessed yearly by DRS into 4 response categories: excellent, indeterminate, biochemical incomplete and structural incomplete.

Results: Median (range) age at diagnosis was 13,7years (5,2-18), 74% were female and 80% pubertal. Median tumor size was 18mm (6-70).49% were multifocal tumors.16% were M1. 35% had thyroiditis. IRS was 16.1%(5) l, 22.6%(7) I and 61.3%(19) H risk. DRS at 3 years revealed 58%(18), 19.3%(6), 6.5%(2) and 16.2%(5) of patients with excellent, indeterminate, biochemical incomplete and structural incomplete response respectively. At 3 years all L risk patients, 86% I and 36% H risk were free of disease. Only 1 patient of the intermediate risk group presented at 2 years a cervical relapse. Characteristics of initial H risk patients were analyzed showing that those with incomplete response at 3 years (7) were initially predominantly prepubertal (P 0.03) with a higher proportion of T4 stage (P 0.05) and M1(P<0.01) than those with excellent response (7).

Conclusions: Our data confirm the aggressiveness of pediatric PTC at presentation. Clinical outcome by DRS at 3 years showed a marked change in the cohort risk composition compared to admission. L risk patients remained free of disease and I patients showed a trend to a better outcome. Half of H risk patients behaved promptly towards a more benign status while in the rest improvement was slower or still incomplete. Yearly DRS assessment provided us useful information allowing a less aggressive approach to those that evolve to NED. These observations reassure the therapeutic intervention.