Study cohorts
Clinical data of all patients diagnosed with lung cancers who were referred to Guangdong General Hospital & Guangdong Lung Cancer Institute (Guangzhou, China) between January 2013 and April 2015 were screened through the electronic medical record system. This study was approved by the Ethics and Scientific Committees of Guangdong General Hospital, and written informed consent forms were signed by all patients. Inclusion criteria were as follows: (1) primary lung cancers treated with RUL and (2) RUL intended to be performed via VATS, including those procedures that were converted to open thoracotomy during surgery. Exclusion criteria were as follows: (1) lung cancers on lobes other than the right upper lobe or (2) lung cancers on the right upper lobe treated with wedge resections, bilobectomy, pneumonectomy, or any other partial/expanded surgery.
Histological subtypes were determined according to the 2015 World Health Organization (WHO) Classification of Lung Tumors [23], and pathologic or clinical staging was based on the seventh edition of the International Association for the Study of Lung Cancer (IASLC) Tumor-Node-Metastasis (TNM) Staging Project [24]. Some advanced cases with intrathoracic dissemination or malignant pleural nodules (M1a) were accidently identified during surgery. As analyzed in previous studies [25] and according to the data of our institute (not published), these M1a patients may benefit from radical resection of the primary tumor lesion and subsequent systemic regimens. These patients with advanced disease receiving surgeries in this study were diagnosed accidentally during surgery. Both patients with early-stage lung cancer and those with accidently diagnosed advanced disease were selected for the analysis.
Perioperative variables
We analyzed some variables related to surgical difficulties, including the maximum diameter and stage of the lesion, the number of dissected lymph nodes (LN) and LN stations, and the presence of fused fissures and intrathoracic adhesion.
Intraoperative variables, including the rate of intraoperative conversion to thoracotomy and corresponding reasons, were analyzed to evaluate surgical feasibility. Reasons for the conversion were classified into two groups: (1) VATS-related reasons, such as vessel injuries, which could be potentially caused by the limited surgical field or VATS procedures and be overcome by thoracotomy; and (2) non-VATS-related reasons, which were associated with intrinsic difficulties mostly due to disease-related anatomical malformations, such as intrathoracic adhesion and dense hilar and interlobar lymphadenectomy. Sometimes the conversion was caused by several reasons; therefore, we evaluated each surgical record to identify the direct reason that made surgeons decide to do the conversion and analyzed the data to explore the potential surgical feasibility and safety.
Postoperative variables, including duration of postoperative chest drainage, postoperative hospitalization, and rates of postoperative complications, were analyzed to compare short-term benefits. Postoperative complications were carefully reviewed and categorized as follows: (1) procedure-specific surgical complications caused by VATS manipulations and (2) non-procedure-specific medical complications resulting from preoperative respiratory, cardiac, or other system diseases.
Surgical approaches
Eligible patients were grouped according to the dissecting order: dissecting the posterior ascending branch first, followed by the right upper bronchus and pulmonary vessels (aBVA); or taking the conventional VAB approach. Specifically, for patients with completely fused oblique fissures, VAB would be chosen because it was more feasible to proceed from the superficial veins toward the deeper arteries and bronchus. However, aBVA was also optimal if the right upper bronchus could be exposed by opening the posterior mediastinal pleura. With other conditions, the surgical approaches were decided by surgeons.
The chief differences between the two surgical approaches were whether the pulmonary vein was dissected first to mitigate potential micrometastasis and whether the bronchus was dissected before pulmonary vessels. Either two ports or a single port was used during aBVA RUL via VATS (Fig. 1) [26]. Surgeons first dissected the visceral pleura at the crossover of the horizontal fissure and posterior oblique fissure. Interlobar lymph nodes were identified and usually regarded as a landmark to expose the posterior ascending arterial branch (“a” in aBVA). Dissection of the posterior ascending arterial branch allowed better exposure of the right upper bronchus. Second, the anterior, superior, and posterior mediastinal pleura around the hilum were dissociated to facilitate dissecting the right upper bronchus with a stapler. Third, a manual tunnel running through the anterior to the posterior hilum facilitated the division of the fused horizontal fissure. Next, the remaining adhesions around the hilum were freed as much as possible. A stapler was used to dissect the remaining branches of the pulmonary arteries and veins (more details in Additional file 1).
The conventional single-direction procedure of VAB RUL proceeds from the anterior to the posterior site, that is, from the superficial to the deeper site [8]. The right upper vein was first dissociated by a stapler after opening the anterior mediastinal pleura, followed by dissecting the right upper arterial branches. Then, the right upper lobe was distracted toward the inferior and posterior sides for clear exposure of the right upper bronchus. After dissociation of adhesions, the right upper bronchus was dissected. The remaining horizontal and oblique fissures were dissected by staplers through a manual tunnel, as performed with the aBVA approach.
Because the selected patients had indications for RUL, systemic node dissection was applied during both surgical approaches to remove the right upper and lower paratracheal, subcarinal, paraesophageal, and pulmonary ligament lymph nodes. Selective lymph node dissection was only performed on patients undergoing wedge resection, who were excluded in this study.
Follow-up
After surgery, patients were followed with computed tomography (CT) scans of the chest and upper abdomen every 3 months for up to 2 years and every year thereafter. When chief symptoms causing suspicions of metastases, such as headache, blurred vision, and ostealgia, were reported during the follow-up period, patients underwent brain magnetic resonance imaging (MRI) every 6 months and bone emission computed tomography (ECT) scans every 12 months to detect potential metastases. The last date of follow-up was on 13 November, 2016.
Statistical analyses
The Statistical Product and Service Solutions (SPSS) software (version 20.0, IBM, Armonk, NY, USA) was used to analyze the data. Categorical variables were analyzed with the Chi square test or Fisher’s exact test. Disease-free survival (DFS) was defined from the date of surgery to the date of disease recurrence or death due to any reason. Overall survival (OS) was calculated from the date of surgery to the date of death. Patients alive at the end of the study were censored at the last follow-up. DFS and OS were estimated using the Kaplan–Meier method and compared between the groups with the log-rank test. A two-sided P value of <0.05 was considered statistically significant.