Is phrenic nerve-sparing worthwhile for phrenic-involved thymic epithelial tumors? A retrospective cohort study.

OBJECTIVES: To determine whether phrenic nerve (PN) sparing offers a worthwhile trade-off between functional preservation and oncologic safety compared with resection in PN-involved thymic epithelial tumors (TETs), and to establish an objective tool for postoperative respiratory risk stratification. METHODS: In this retrospective cohort of patients with TETs with PN invasion, 122 propensity score-matched cases were analyzed from 2016 to 2024. PN preservation or resection was determined intraoperatively based on the extent of invasion. The diaphragmatic elevation (DE) ratio was calculated as [(preoperative diaphragm-apex distance - postoperative distance)/preoperative distance] × 100% according to X-rays, and cutoff values were defined by respiratory complication risk. Perioperative and oncologic outcomes were compared between the PN-sparing and PN resection groups. RESULTS: Overall perioperative morbidity and recovery outcomes were comparable between the PN-sparing and PN-resection groups; however, tumor progression was significantly more frequent on the PN-sparing group (39.3% vs 23.0%), resulting in worse progression-free survival (PFS) (P = .027), although overall survival (OS) remained comparable in the 2 groups. Multivariable analysis identified PN preservation as an independent predictor of progression (P = .049). Furthermore, our receiver operating characteristic-derived DE classification scheme (mild, ≤15%; moderate, 15-25%; severe, ≥25%) predicted severe postoperative respiratory complications (P < .001). CONCLUSIONS: PN resection improves PFS without increasing severe perioperative complications, although OS is comparable to that with PN-sparing.