Apparent Survival Benefit of Postoperative Radioactive Iodine in Lymph Node-Positive Papillary Thyroid Carcinoma: A Negative-Control Analysis for Unmeasured Confounding

Background

Observational studies report an overall-survival advantage for postoperative radioactive iodine (RAI) in lymph node-positive papillary thyroid carcinoma (PTC), but such estimates are vulnerable to confounding by indication and to bias from immortal time and the healthy-user effect. We assessed the credibility of this apparent benefit rather than RAI efficacy itself.