Disease Progression in Papillary Thyroid Cancer with Biochemical Incomplete Response to Initial Therapy.

Background: Dynamic risk stratification is utilized in the follow-up of patients with papillary thyroid carcinoma (PTC). Analysis of outcomes after biochemical incomplete response (BIR) to initial therapy will allow better individualization of care.

Methods: A total of 494 patients with PTC were followed prospectively. Immunohistochemistry (IHC) for BRAF mutation was completed on all surgical specimens. After exclusion of patients with inadequate data, 353 patients were stratified into four categories of response to initial therapy: excellent, biochemical incomplete, structural incomplete, or indeterminate. Patients with BIR, defined as elevated stimulated thyroglobulin >2 µg/L with negative imaging, were analysed for progression of disease. The primary outcome measure was development of structural recurrence.

Results: Forty-nine of 353 (13.9%) patients had BIR. BRAF mutation was present in 32 of 49 (65.3%) with BIR. Progression to structural recurrence occurred in 8 of 49 (16.3%) with BIR, all of whom were positive for the BRAF mutation (p = 0.02). Nine patients (18%) with BIR remitted during follow-up to no evidence of disease (6 had additional RAI therapy). After mean follow-up of 35 months, 12 patients with BIR (24%) remained biochemically abnormal with no structural evidence of disease.

Conclusions: Patients with BIR following initial treatment for PTC have generally favorable outcomes. Positive IHC for BRAF identifies patients at risk of structural disease recurrence.