In this study, we compared survival results of patients with stage I NSCLC ≤ 2 cm treated by wedge resection, segmentectomy, lobectomy. Our study showed patients received wedge resection had obviously worse OS and borderline significant worse LCSS than lobectomy in patients with NSCLC ≤ 1 cm.The OS and LCSS were significant worse in patients receive wedge resection than lobectomy with NSCLC>1 to 2 cm. No statistical significance was observed in OS and LCSS between segmentectomy and lobectomy in both patientswith NSCLC ≤ 1 cm and NSCLC>1 to 2 cm. LND turned out to be an independent risk factor for better OS in patients with NSCLC ≤ 1 cm. For patients with NSCLC>1 to 2 cm, LND was associated with better OS and LCSS.
With the wider use and higher resolution of computed tomography (CT)screening for lung cancer, more and moreearly stage lung cancers are being detected.A randomizedcontrolled trial in early years showed lobectomy was superior to limited resection for patients with stage I NSCLC ≤ 3 cmwith lower death rate and locoregional recurrence rate[4]. However,the results of this study may not able to generalize to patients nowadays since the operative skills and histology of early stage NSCLC had changed a lot in the past few years.Several recently published studies showed comparable OS between lobectomy and sublobar resection in stage IA NSCLC[12-13]. The optimal surgical procedure for stage IA NSCLC remains controversial. Since the International Association for the Study of Lung Cancer (IASLC) lung cancer proposed to divideT1a into new T1a(≤ 1 cm) and T1b (>1 to 2 cm)in the eight edition TNM stage classification for lung cancer, a lot of attention has been focused on whether there is substantial difference in extent of lung resection for new T1a to T1b.
Beside extent of lung resection, whether LND is needed for early stage NSCLC is also controversial.Several randomized controlled trial compared survival between LND and lymph node sampling (LNS)[6,7,14]. Wu and colleagues suggested LND had obviously better survival compared with LNS for stage I NSCLC [6]. Sugi and colleagues showed no statistical significance was observed between LND and LNS in peripheral non-small-cell lung cancer less than 2 cm in diameter in their study [7].ACOSOG Z0030 trial also showed mediastinal lymph node dissection does not improve survival in patients with early stage non-small cell lung cancer [14]. However, in ACOSOG Z0030 trial, mediastinoscopy was widely used and randomization was after negative mediastinal nodal sampling, so the results were not generalizable to patients staged radiographically. In studyperformed by Sugi et al [7], the number of included patients is too small to achieve a valid conclusion.
In our study, we found segmentectomy had comparable OS and LCSS compared with lobectomy in NSCLC ≤ 1 cm and NSCLC>1 to 2 cm ,which was contradict with previous study performed by Dai et al [9] that also used SEER data. There are several reasons contribute to above results. Firstly, compared with previous study, more recently published SEER data were used in our study. In the past years, more and more ground glass-opacity nodules were detected, and several studies showed satisfactory survivalwere obtained after limited resection among these patients[15-18]. The different composition of histology may result in different survival status in our study. Secondly, extent of lymphadenectomy was not analyzed in previous study. Our study showed LND turned out to be an independent risk factor for better OS in patients with NSCLC ≤ 1 and better OS and LCSS for patients with NSCLC>1 to 2 cm. Without analysis of the status of lymphadenectomy, selection biases would inevitable exist in previous study and may explain the survival differences between two studies.
It is generally accepted LND can provide more accurate pathological stage for NSCLC when compared with non-LND. So, patients with non-LND may have more understaged patients than patients with LND, which may result in worse survival in non-LND group. Previous study concluded sublobar resection may result in more understaged lung cancers because of inadequate lymphadenectomyfor hilar (N1) lymph nodes compared with lobectomy [19]. However, our study showed 61.1% patients in segmentectomy group, 75% patients in wedge resection group had less than or equal to 5 lymph nodes examined, which was even higher than lobectomy without LND group (55.4%) in NSCLC ≤ 2 cm. So the major reason for more understaged patients in sublobar resection group compared with lobectomy groupin this study may attribute to lacking LND other than inadequate lymphadenectomy for hilar (N1) lymph nodes. After status of lymphadenectomy was analyzed in this study, no statistical survival difference was observed between segmentectomy and lobectomy. However, wedge resection still had worse OS in NSCLC ≤ 2cm and worse LCSS in NSCLC>1 to 2 cm compared with lobectomy.
Compared with lobectomy, sublobar resection has the advantages of preserving better pulmonary function, fewer complications and lower mortality [20-21],which is widely used in patients withNSCLC cannot tolerate a lobectomy due to compromisedpulmonary function or advanced age. It is interesting to notice that the rate of segmentectomy(5.7%) is obviously lower than wedge resection (23.0%) and lobectomy (71.3%) in this study. More technically demanding than wedge resection and possibly worse survival than lobectomy may contribute to above situation. Since segmentectomy has advantages of better survival than wedge resection, preserving better pulmonary function and having comparable survivalcompared with lobectomy, segmentectomy should be encouraged to perform for patients with NSCLC ≤ 2 cm, regardless with or without compromised pulmonary function.
Compared with LNS, LND adds little morbidity to a pulmonary resection for lungcancer[22]. However, the impact on the operative process or postoperative course is limited. Our study showed obviously better OS and LCSS in lobectomy with LND group compared with lobectomy without LND group both in patients with NSCLC ≤ 1 and NSCLC>1 to 2 cm. Multivariable analysis suggested LND was independent risk factor for better OS in patients with NSCLC ≤ 1 and NSCLC>1 to 2 cm. Under this circumstance, LNDshould also be encouraged to perform for patients with NSCLC ≤ 2 cm, regardless extent of lung resection.
There were certain some limitations in this study. Given its retrospective nature, selection biases in treatment allocation were inevitable exist, although advanced statistical methods were applied in this study. Patients with limited cardiopulmonary function, elderly people were more likely to be allocated to sublobar group. However, the cardiopulmonary function situation was not given in our study, which was not able to balance by advanced statistical methods.Although comparing LCSS can exclude the influence of cardiopulmonary function situation in the maximum extent, this limitation could havea little impact on our results. Besides, we classified sublobar resection group as without LND group, which specific code was not provided in SEER database. Although the rate of examined lymph node less than or equal to 5 lymph nodes in sublobar resection was even higher than lobectomy without LND group, there was still a chance that small proportion of patients in sublobar resection received LND, which may have a little influence on our results.