Sublobar resection is not usually recommended for the treatment of stage IB NSCLC. However, because visceral pleural invasion is diagnosed only after surgery, it is sometimes diagnosed as postoperative stage IB when sublobar resection was performed for small peripheral nodules. In this study, sublobar resection for small-sized (invasive component size ≤ 2 cm) stage IB NSCLC had comparable prognosis with lobectomy. Firstly, we compared the prognosis between patients with small-sized stage IB NSCLC who underwent sublobar resection and patients with any stage IB NSCLC who underwent lobectomy. All patients were consecutive patients in the same hospital and underwent the same treatment protocols; moreover, both groups were well matched in clinicopathological characteristics except SUVmax and invasive component size. Thus, we then compared the prognosis of sublobar resection and lobectomy in patients with small-sized stage IB NSCLC. In this analysis, all clinicopathological characteristics were well matched and RFS and OS rate were not different in the statistical analysis. Furthermore, sublobar resection was not a risk factor for recurrence in 2 multivariate analyses in this study. Therefore, we concluded that sublobar resection for small-sized stage IB NSCLC had the same prognosis as lobectomy. In other words, these patients may not need an additional completion lobectomy performed immediately.
After implementation of the eighth revision of the TNM classification of NSCLC, the composition of the tumors included in the stage IB classification was changed. Most importantly, the requirement for measuring tumor size was changed. Determination of the T stage in the eighth revision is based only on the maximum dimension of the invasive component and excludes the lepidic component [13, 15]. The size range of the T2a descriptor was also reduced from 3 to 5 cm to 3 to 4 cm. Therefore, the tumor characteristics for the seventh edition stage IB NSCLC were changed in the eighth edition. Because of these changes, we thought that if the stage-based postoperative prognosis is studied, in all cases it is necessary to restudy after applying the eighth edition of TNM staging. This study is also the first to study the prognosis of sublobar resection of stage IB by applying the eighth edition of the TNM staging system.
Sublobar resections are usually performed for small-sized peripheral tumors in our institution. Particularly, patients with GGO tumors (consolidation : tumor ratio < 0.5) were candidates for intentional sublobar resection. Ten patients (47.6%) underwent intentional sublobar resection in this study. On the other hand, 7 patients underwent sublobar resection because of a poor general health condition (underlying cardiopulmonary disease, underlying hematologic malignant disease, and old age). Four patients underwent sublobar resection because of previous contralateral lung surgery. Although the sublobar resection group was not homogenous and the decisions for performing sublobar resection were varied, all study data were collected from consecutive patients who underwent curative surgery at 1 institution and clinicopathological characteristics were not different between the sublobar resection group and the lobectomy group. Thus, the findings of this study are considered meaningful.
The tumors of the sublobar resection group were located near the visceral pleura. Those tumors all invaded the visceral pleura, so their stage was upstaged from clinical T1a-b to pathological T2a. The tumors were all attached to the visceral pleura, making wedge resection and segmentectomy relatively uncomplicated to perform. It was also easy to ensure sufficient margins after sublobar resection. Studies have shown that the resection margin should be at least the tumor size when sublobar resection is performed [16–18]. In this study, not only was the resection margin longer than the tumor size, but more sufficient lung parenchyma was removed. In the case of tumors adjacent to the visceral pleura, the resection margin can be sufficiently excised even by sublobar resection. Therefore, it may be assumed that sublobar resection might be as effective as lobectomy even for peripheral small-sized stage IB.
There have been few studies analyzing the prognosis of sublobar resection in stage IB NSCLC. This is because, at stage IB, it is generally accepted that lobectomy should be performed. Our previous study reported that sublobar resection for small-sized (≤ 2 cm) NSCLC with visceral pleural invasion or lymphatic invasion had a similar prognosis as lobectomy . Of course, the previous study yielded similar results to the current study; however, the previous study included patients with lymphatic invasion, while the current study included only patients with visceral pleural invasion. Among the cases of visceral pleural and lymphatic invasion, only visceral pleural invasion is the upstaging factor. This is because only visceral pleural invasion can upstage small lung cancers, leading to stage IB. The previous study was based on the seventh edition TNM staging system, while the current study adopted the eighth edition of the TNM staging system. Furthermore, previous studies have included large numbers of patients before 2010; however, this study consists only of data since 2010. This study, which contains relatively new data and adopts the new TNM staging system, is expected to predict more accurate results than previous studies of sublobar resection for small-sized stage IB NSCLC.
This study has a few limitations. First, it was a retrospective review. Second, we obtained data from a single institution, and the sample size was relatively small from which to generalize our results. However, this study examined data from surgical patients treated with a standardized protocol at an institution, a tertiary hospital in Korea. Furthermore, a very detailed analysis was possible because of the comprehensive information stored in the electronic medical record. We also had no problem applying the new staging system using pathology slides. We believe that our data will be useful as the basis for future investigations. A prospective randomized controlled study should be performed to validate our results. Finally, patients with a short follow-up period were included in this study. However, most patients with NSCLC are known to have disease recurrence within a 2-year postoperative period , and early recurrence has been shown to be an accurate reflection of long-term outcomes .
In conclusion, the prognosis of sublobar resection in patients with small-sized (≤ 2 cm) stage IB NSCLC was comparable with lobectomy. Thus, additional completion lobectomy is not essential in this setting, despite postoperative upstaging from T1 to T2a. Further research through multicenter randomized controlled trials may more accurately depict patient outcomes.