Surgical Morbidity and Short-Term Oncologic Status after Prophylactic-Intent Thyroidectomy in a Cohort of Children with MEN2 from the Multicenter GTE ENDOCAN-RENATEN Study.

BACKGROUND: Children carrying germline RET mutations associated with multiple endocrine neoplasia type 2 (MEN2) are at high risk of developing medullary thyroid carcinoma (MTC). Prophylactic-intent thyroidectomy is recommended during childhood to prevent progression to advanced disease. Genotype-based recommendations combined with calcitonin measurements allow more individualized surgical timing. However, performing thyroidectomy at very young ages may expose children to long-term morbidity, particularly permanent hypoparathyroidism.

METHODS: We conducted a retrospective national multicenter cohort study within the French Groupe d'Étude des Tumeurs Endocrines, including children younger than 15 years who underwent prophylactic-intent total thyroidectomy between 2010 and 2020 in the absence of clinically apparent structural disease. Data collected included RET genotype, age at surgery, preoperative calcitonin values interpreted relative to each laboratory's upper limit of normal, surgical procedures performed, histopathologic findings, postoperative complications, and clinical status at last follow-up.

RESULTS: Sixty-four children (61 MEN2A, 3 MEN2B) underwent surgery at a median age of 4.6 years (interquartile range [IQR] = 3.2-8.3 years). Preoperative calcitonin was elevated in 44% of evaluable patients. Histopathology demonstrated C-cell hyperplasia in 52% and micro-MTC in 34%, while lymph node metastases were rare (3%). After a median follow-up of 6 years (IQR = 2.4-8.5 years), no patient had persistent structural disease. One patient had persistent moderate biochemical disease without structural evidence of MTC, although follow-up duration limits definitive long-term oncologic outcomes. Postoperative morbidity was notable: hypoparathyroidism occurred in 31% of patients and was permanent in 16%, predominantly among children operated before age 5 years.

CONCLUSIONS: In this national contemporary cohort, prophylactic-intent thyroidectomy in pediatric MEN2 was associated with excellent short-term oncologic outcomes but also with a substantial rate of permanent hypoparathyroidism, particularly in very young children. These findings underscore the importance of multidisciplinary evaluation of both the timing and extent of surgery in expert centers.