Pediatric thyroid cancer: Postoperative classifications and response to initial therapy as prognostic factors

Context: Prognostic factors for pediatric differentiated thyroid cancer (DTC) are not well established. Objective: The objective of the study was to retrospectively compare the postoperative risk-stratification systems: American Thyroid Association (ATA) risk categories, Schneider Children's Medical Center of Israel (SCMCI) score, and the response to initial therapy as predictors for disease outcome. Patients and Methods: Fifty-four DTC patients, median age at diagnosis 13.9 years (range 1.9-17 y), followed up for a median of 8.8 years (range 2.6-20.5 y) were stratified into prepubertal (n = 9), pubertal (n = 25), and postpubertal (n = 20) groups. All patients underwent total/near-total thyroidectomy; 48 received radioiodine therapy. The extent of DTC was evaluated by applying the ATA risk categories and the novel SCMCI score. Postoperative risk stratifications (low/intermediate/high) were determined using histopathological, laboratory, and imaging findings. Response to initial therapy (complete/acceptable/incomplete) was based on stimulated thyroglobulin and imaging results during the first 2 years of follow-up. Results: The risk for recurrent/persistent disease, as assessed by the postoperative ATA risk-stratification system and the SCMCI score and by the response to initial therapy, was higher in the prepubertal group (P < .001, P = .002, and P = .02, respectively). Outcome prediction by the risk-stratification systems was applicable: ATA risk categories, P = .014, R² = 0.247, predictive ability 80.4%; SCMCI score, P < .001, R² = 0.435, predictive ability 86.3%; and response to initial therapy stratification, P < .001, R² = 0.789, predictive ability 96.1%. The proportion of variance explained by the ATA risk categories (0.25), SCMCI score (0.44), and response to initial therapy (0.79) indicated that the latter was the most precise predictor and that the SCMCI score reflected the disease outcome better than ATA risk categories. Conclusions: Our data confirm that the postoperative pediatric ATA stratification system and the novel SCMCI score are suitable for predicting the risk of recurrent/persistent disease in this population. The response to initial therapy classification performed 1-2 years after the initial therapy may be more appropriate for guiding surveillance recommendations.