In recent years, with the application of neoadjuvant chemoradiotherapy + surgery + adjuvant therapy and other treatment modes, the survival rate of esophageal cancer patients has improved, but 5-year overall survival rate is still less than 35% in the world. Several studies [16, 17] have shown that the poor prognosis of esophageal cancer is mainly related to the recurrence and metastasis of postoperative lymph nodes, especially the recurrence and metastasis of bilateral recurrent laryngeal nerve chain lymph nodes. Therefore, in the radical operation of esophageal cancer, the dissection of bilateral recurrent laryngeal nerve chain lymph nodes is extremely important. Lymph node dissection of the bilateral recurrent laryngeal nerve chain can undoubtedly improve the staging accuracy of patients with esophageal cancer and improve the prognosis of patients to a certain extent, but it also increases the incidence of recurrent laryngeal nerve injury [18–20].
When performing bilateral recurrent laryngeal lymph node dissection, the incidence of recurrent laryngeal nerve palsy after surgery ranges from 13–80% [9, 21–23]. Compared to the right recurrent laryngeal nerve, the incidence of the left recurrent laryngeal nerve palsy is higher. In this study, the rate of RLNI was 31.9% in all patients, left-side RLNI occurred 2.8 times more often than right-side RLNI. Regarding the rate of the RLNI, our center has a higher incidence than previous studies [19, 24, 25]. There are some reasons: First, our center uses fiberoptic bronchoscopy to observe vocal cord activity to determine whether the recurrent laryngeal nerve is damaged. On the one hand, the vocal cord activity is checked, and on the other hand, the patient is suctioned to prevent pneumonia. In other centers, RLNI was either diagnosed or previously suspected by clinical symptoms. Second, the stretching, bending, and thermal damage for the nerve might be the reason for it during LN dissection. Third, after the tracheal intubation is removed, we examined the vocal cords by the fiberoptic bronchoscopy routinely. In some patients, the recurrent laryngeal nerve injury is caused by tracheal intubation probably due to the nerve's ischemic change, which may be significantly improved after one or two days.
In this study, we found that patients with RLNI have a longer operation time of chest and higher incidence of postoperative complications, especially respiratory complications. Our results could be explained from the following points: First, the longer the operation time, which means that the surgical trauma is greater, and it is more likely that it will take longer to clean the recurrent laryngeal nerve chain lymph nodes, resulting in a higher probability of RLNI; Second, the RLNI can cause temporary or permanent injury of vocal cord, which cuould cause serious persistent hoarseness, weak cough and expectoration leading to postoperative pneumonia, tracheal intubation or tracheotomy is needed in severe cases, and it will affect patients' postoperative rehabilitation and quality of life, and is even life-threatening. Therefore, we do believe that RLNI will adversely affect the short-term prognosis of patients and should be avoided as much as possible during the operation.
There is no consensus on whether postoperative complications of esophageal cancer will affect the overall survival of patients. Most scholars [26, 27] reported that postoperative complications will have a negative impact on the long-term survival. However, some scholars [28, 29] found that postoperative complications will not affect long-term prognosis. In terms of RLNI, researchers [19, 20, 22] has found that it can adversely affect the short-term prognosis of the patient, but it is still unknown whether it will affect the long-term prognosis. To our best knowledge, this study is one of the few studies on the long-term prognosis of patients with RLNI after esophagectomy. Using Cox Multivariate regression analysis, we found that T stage, N stage, and RLN LN metastasis were independent prognostic factors of OS, but RLNI did not affect OS (HR = 1.412,95% CI:0.892–1.543,P = 0.056). Through our postoperative follow-up, we also found that patients with hoarseness generally recover within 3–6 months after surgery, and it is extremely rare to have water cough and eating difficulties, which is consistent with the Baba M et al [25]. Therefore, we believe that major of the recurrent laryngeal nerve injury is temporary, most patients can recover through functional exercise and nutritional neurotherapy after surgery, so there is no significant effect on the overall survival of patients.
However, our study had some limitations and shortcomings. The first and a major limitation of this study is its retrospective nature, thus, the selected bias definitely existed. Second, there was no subgroup analyses between different clinical stage with RLNI in the study. However, there was no significant difference in general clinical data between the two groups of patients in the study, which may compensate for this deficiency. Last, the sample size of this study in the single institution is small, and it needs to be confirmed by prospective, multi-institutional and large sample studies in future.