Pediatric thyroid cancer lung metastases and RAI: long-term results

Children with differentiated thyroid cancer (DTC) often present with lung metastases but historically have good outcomes. Radioactive iodine (RAI) is commonly used to treat these children. Given the rarity of this condition, little evidence detailing long-term outcomes and risk of radiation pneumonitis exists.

We conducted a retrospective analysis of patients <20 years old who received RAI for DTC lung metastases between 1973 and 2018. Disease-free survival (DFS) was calculated from diagnosis to last follow-up. Overall survival and rates of acute and late radiation pneumonitis were determined by chart review and obituary searches.

Sixteen patients met eligibility criteria. Fourteen presented with thyroid, nodal, and lung disease; one presented with thyroid and nodal disease with nodal and lung recurrence; and one presented with thyroid-only disease with nodal and lung recurrence. All patients underwent thyroidectomy, 10 underwent neck dissection, and four underwent lymph node excision. Median per-treatment and cumulative RAI dose were 100 mCi (20-270 mCi) and 340 mCi (25-970 mCi), respectively. Median follow-up was 13 years (1-32 years). Fifteen patients (88.2 %) were alive at last follow-up. Twelve had no evidence of disease, two had improved but persistent I-131 uptake within lungs and surgical bed, and one had improved but persistent lung metastases alone. No evidence of symptomatic radiation pneumonitis was evident in the medical records of these patients.

Patients <20 with DTC lung metastases have high survival following thyroidectomy and RAI treatment and apparently low rates of radiation pneumonitis despite high cumulative doses.