This study investigated whether ‘lung age’ could be a useful parameter for the prediction of postoperative complications and long-term survival in patients with esophageal cancer followed by MIE. There have been extensive studies focusing on MIE with poor pulmonary function[6, 14, 15]. However, the PFT result may be difficult to understand. There have been no reports about MIE about the use of this new concept before now, and our study is the first investigation into the association between ‘lung age’ and short-term and long-term postoperative outcomes.
Our results suggested that male, COPD, ASA status was significantly associated with group classification based on difference of lung age and real age. Furthermore, there was also an association between smoking status and index. Smoking is not only risk factor for esophagus cancer, but also for COPD[16, 17]. The concept of ‘lung age’ was firstly proposed to motivate smoking cessation or COPD treatment. Inoue J et al. reported that intensive preoperative respiratory rehabilitation could reduce incidence of postoperative pulmonary complications in esophageal cancer patients who underwent esophagectomy[18]. ‘Lung age’ could be a parameter to explain pulmonary function and may improve the adherence of smoking cessation before and after operation. For thoracic surgeons, lung age or the difference of lung age and real age could also help to find patients with impaired pulmonary function and give these patients preoperative respiratory rehabilitation to avoid negative events.
Through multivariate analysis, we found L-R, CHD, 3 field lymphadnectomy were risk factors of severe postoperative complications(CCI > 30). Previous studies have confirmed that patients with impaired pulmonary function are associated with increased risk of postoperative complications, longer hospital stay, and heavier economic burden[7, 19–22]. Klevebro, F et al. concluded that FEV1/FVC ratio < 70% was associated with increased risk of overall postoperative complications, cardiovascular complications, atrial fibrillation, pulmonary complications, and pneumonia[7]. Maruyama S et al. concluded that the airflow limitation measured by FEV1% can help predict the occurrence of pneumonia after esophagectomy in patients with and without COPD[19].Merritt RE et al. also reported that FEV 1%< 60% is associated with major morbidity[20].Our results also confirmed that patients with impaired pulmonary function are associated with increased risk of severe postoperative complications, more hospital cost, and longer postoperative hospital stay. L-R is a novel parameter of impaired pulmonary function. Compared with FEV1%, FEV1/FVC, or other parameters from PFT report, L- R is easier to be understood by patients, and has extensive clinical application value.
Our results showed that CHD was associated with increased risk of severe postoperative complications. This conclusion is consistent with previous report. F. Klevebro et al. concluded that cardiac comorbidity is associated with increased risk of cardiovascular and pulmonary complications, respiratory failure, and Clavien–Dindo score ≥ IIIa[7]. Merritt RE et al. concluded that preoperative coronary artery disease is a risk factor of major postoperative complications after esophagectomy following neoadjuvant chemoradiation[20]. Patients with CHD are more prone to postoperative pulmonary edema due to heavy volume load. Further, patients with CHD may have a state of low cardiac output, leading to insufficient perfusion of terminal organs. This state of low cardiac output may also have adverse effects on anastomosis[20, 21].
Although many studies have compared the short-term and long-term results between 3-field lymph node dissection and 2-field lymph node dissection for esophageal cancer[18, 22–24], there is still not a consensus on whether 3-field lymph node dissection would increase the postoperative complications. A meta-analysis including 20 studies(2 randomized studies and 18 observation studies) over 7000 patients, showed that 3-field lymph node dissection was associated with a higher incidence of postoperative complications, especially anastomotic leakage and recurrent nerve palsy. However,this result is limited by high heterogeneity[24]. Yamashita K et al. reported that after (propensity score matching) PSM analysis 3-field lymph node dissection had similar postoperative complications with 2 field lymph node dissection[26]. Recent PSM analysis showed that 3-field lymph node dissection resulted in more postoperative complications[25]. Our results supported that three-field lymph node dissection had a high risk of severe postoperative complications. The strength of evidence in this study was using CCI as quantitative indicators to evaluate postoperative complications.
A history of COPD is one of the most common conditions, accounting for 11.5% of newly diagnosed esophageal squamous cell carcinoma cancer patients(ESCC), 8.64% in this study. Previous reports showed that COPD is associated with worse prognosis[27–30]. Recently, Zhao Z et al. established a nomograms model to predict individual survival after curative esophagectomy for ESCC, and COPD is one of independent prognostic variables[27]. In this study, there was a significant difference of OS between group A(L-R ≦ 0)and group B + group C(L-R > 0)(P = 0.03). We contribute the OS difference to following factors: First, immune dysfunction plays an important role in the development of impaired pulmonary function, which also promote the rapid progression of microscopic residual disease into clinical manifestations of recurrence[29]. Second, impaired pulmonary function has been found to be a risk factor for postoperative pulmonary complications. Postoperative pulmonary complications may be associated with poorer prognosis[28, 30]. Thus, it may be necessary to conduct a more strict follow-up plan for patients with L-R > 0.
The strength of this study is relatively large sample size, relatively standardized surgical procedures and perioperative management. However, this study is limited by retrospective nature, and only conducted in single institution. The majority of patients in this study were diagnosed with esophageal squamous cell carcinoma. Further, most patients underwent trans-thoracic procedure. We tried to solve the potential selection and detection bias by strict patient selection and postoperative complication only limited in hospital stay rather than 30-day or 90-day. In order to further verify the reliability of conclusions in patients with esophageal adenocarcinoma, prospective multicenter studies are necessary.