Cancer medicine
Apparent Survival Benefit of Postoperative Radioactive Iodine in Lymph Node-Positive Papillary Thyroid Carcinoma: A Negative-Control Analysis for Unmeasured Confounding
By Liu T, Qiao J, Mao M and 2 others.
Abstract
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.
Methods
Using SEER (2010-2015), we assembled a cohort of N1b, M0, totally thyroidectomized PTC patients and applied a 3-month landmark analysis (sensitivity analyses at 1 and 6 months) with stabilized inverse-probability-of-treatment weighting. We estimated RAI effects on overall survival, cancer-specific survival, and relative survival, and on a negative-control outcome-non-thyroid-cancer death-that RAI cannot plausibly affect. Residual confounding was quantified with E-values.