CONTINUOUS AND INTERMITTENT RECURRENT LARYNGEAL NERVE MONITORING IMPROVES SUPERIOR MEDIASTINAL DISSECTION FOR ESOPHAGEAL SQUAMOUS CELL CARCINOMA
Ian Yu Hong Wong*, Ruiqi Zhang, Raymond King Yin Tsang, Fion Siu Yin Chan, Kwan Kit Chan, Claudia Wong, Tsz Ting Law, Simon Law
Queen Mary Hospital, The University of Hong Kong, Hong Kong, Hong Kong
Background
For esophageal squamous cell carcinoma (ESCC), the rate of recurrent laryngeal nerve (RLN) lymph node (LN) metastasis ranges from 15-32%, depending on the site of primary tumour. However, RLN injury rate can be as high as 60-70% after superior mediastinal dissection. The authors have previously described the use of combination of continuous and intermittent RLN nerve monitoring during esophagectomy. This study compared the results before and after the implementation of such protocol.
Methods
This is a retrospective case-control study utilizing a prospectively managed database. All ESCC patients who had esophagectomy from 2003 - 2019 were included. Patients with cervical esophageal tumour, transhiatal resection, preoperative vocal cord (VC) palsy, incomplete operative record and lacking postoperative VC assessment were excluded. After 2014, RLN monitoring protocol using both continuous and intermittent nerve monitoring during left RLN lymphadenectomy and intermittent nerve monitoring only over right side was adopted. RLN lymphadenectomy was not performed when there was poor exposure, R2 resection, uncertain contralateral nerve integrity, high-risk patients with no clinical demonstratable nodes or presence of technical difficulties/complications. The actual number of RLN LNs harvested and VC palsy rate was analysed. The factors affecting vocal cord palsy were also analysed using binary logistic regression.
Results
Four hundred and eighty patients were included. Among which, 124 patients underwent "nerve monitoring protocol" and 356 patients underwent routine esophagectomy. Patient demographics are presented in Table 1. The percentage of cases with RLN lymphadenectomy performed and number of RLN LN harvested per case increased after the year 2014. Temporary and permanent VC palsy rates were low after 2015. (Figure 1). Considering the learning curve of this procedure, the overall palsy rate dropped after the first 2 years (42 cases) from 31.0% to 15.9% (later 82 cases), with a near statistically significant p-value of 0.051. Within the nerve monitoring group, lymphadenectomy was performed in 56.5% (both sides), 86.3% (right) and 57.3% (left). Mean RLN LNs harvested per patient is 4.66 compared to 0.6 in routine group (p<0.0001). The overall VC palsy rate was 21% and permanent (>1 year) VC palsy rate was 8.1% in nerve monitoring group. In multivariate analysis, neoadjuvant therapy (OR 1.844, p=0.012) and upper esophageal tumour (OR 2.727, p=0.001) were independent factors affecting VC palsy.
Discussion
Continuous and intermittent recurrent laryngeal nerve monitoring can increase the confidence of the surgeon and the actual number of LNs harvested during superior mediastinal dissection. The VC palsy rate was not jeopardized. The oncological safety of selective RLN dissection and cost-effectiveness of such protocol is yet to be proven.
Patient Characteristics
Time trend of RLN lymphadenectomy, RLN LN harvested and VC palsy rates
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