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

Abstract

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. A total of 494 patients with PTC were followed prospectively. Immunohistochemistry (IHC) for BRAF^V600E 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. Forty-nine of 353 (13.9%) patients had BIR. BRAF^V600E 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^V600E 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. Patients with BIR following initial treatment for PTC have generally favorable outcomes. Positive IHC for BRAF^V600E identifies patients at risk of structural disease recurrence.