Recurrent Laryngeal Nerve Invasion by Thyroid Cancer: Laryngeal Function and Survival Outcomes

Abstract

Background: Recurrent laryngeal nerve (RLN) invasion by thyroid carcinoma represents an advanced disease status with potentially significant co-morbidity. Methods: In a retrospective single-center study, we included patients with invaded RLNs operated on while using nerve monitoring techniques. We studied pre-, intra-, and postoperative parameters associated with postoperative vocal cord paralysis (VCP); 5-year recurrence-free survival (RFS); and 5-year overall survival (OS) in addition to two subgroup analyses of postoperative VCP in patients without preoperative VCP and based on source of RLN invasion. Results: Of 65 patients with 66 nerves-at-risk, 39.3% reported preoperative voice complaints. Preoperative VCP was documented in 43.5%. The RLN was invaded by primary tumor in 59.3% and nodal metastasis in 30.5%. Papillary thyroid carcinoma was the most common pathologic subtype (80%). After 6 months, 81.8% had VCP. Complete tumor resection of the RLN was not associated with 5-year RFS (p = 0.24) or 5-year OS (p = 0.9). Resecting the RLN did not offer statistically significant benefit on 5-year RFS (p = 0.5) or 5-year OS (p = 0.38). Radioactive Iodine (RAI) administration was associated with improvement in 5-year RFS (p = 0.006) and 5-year OS (p = 0.004). Patients without preoperative VCP had higher IONM amplitude compared with patients with VCP. After a mean follow-up of 65.8 months, 35.9% of patients had distant metastases, whereas 36.4% had recurrence. Conclusion: Preoperative VCP accompanies less than half of patients with RLN invasion. Invaded RLNs may have existent electrophysiologic stimulability. Complete tumor resection and RLN resection were not associated with better 5-year RFS or OS, but postoperative RAI was. Level of Evidence: 4 Laryngoscope, 132:2285–2292, 2022.