Assessment of pulmonary function after lobectomy for lung cancer — upper lobectomy might have the same effect as lung volume reduction surgery

Lung volume reduction surgery (LVRS) has been associated with improved lung function in patients with pulmonary emphysema by resection of relatively functionless emphysematous lung [1–5]. Recently, some researchers reported that lobectomy in selected patients with lung cancer and severe emphysema was favored by no change or improvement in postoperative pulmonary function [6–11]. Moreover, chronic obstructive pulmonary disease (COPD) patients with lower forced expiratory volumes in one second (FEV1.0) might have less pulmonary function loss after lobectomy [8,9]. We hypothesized that lobectomy would provide the same volume reduction effect as LVRS to some extent in patients without COPD on the pulmonary function test (PFT), as most of the patients with lung cancer had more or less emphysematous changes [12]. In other words, lobectomy would have the effect of both loss and gain on pulmonary function caused by resection of normal lung tissue and emphysematous lung tissue, respectively. We assessed the change in pulmonary function after lobectomy in patients with lung cancer from a standpoint of a lobar volume reduction effect. We retrospectively reviewed 401 patients who underwent lobectomy for non-small cell lung cancer (NSCLC) in our institution between January 1995 and December 2003. Twenty-two patients undergoing right middle lobectomy were excluded from this study. To current smokers, we performed surgery since 1 month after smoking cessation. We excluded patients who did not quit smoking postoperatively (n = 8). We also excluded patients who had adjuvant chemotherapy or radiotherapy (n = 62), who had postoperative empyema or severe pulmonary complications (n = 15), or who had air space on postoperative chest roentgenograms (n = 2). Furthermore, we excluded patients who had segmental or lobar atelectasis preoperatively (n = 62), or who had a tumor with a diameter size of more than 4 cm (n = 45) because any non-function of the resected lung tissue was not necessarily due to emphysema. We also excluded one patient who had stridor on slight effort, and persistent collapse of the right middle lobe after right upper lobectomy, and four patients who had stridor on slight effort after left upper lobectomy. They had strongly impaired pulmonary function after lobectomy, which was greater than expected because they had severe narrowing of the orifice of the right intermediate bronchus or left lower bronchus on postoperative bronchoscopy. The total number of patients on whom this study was conducted after all unsuitable patients were excluded was 178. Pulmonary function tests were performed at first visit to our department and repeated immediately before surgery. We adopted the data of PFTs repeated immediately before surgery. PFTs were performed 6 months to 1 year after lobectomy. The mean time interval between lobectomy and postoperative pulmonary function test was 7.8 ± 1.7 months. Postoperative pulmonary function data were not available in 20 patients who were unable to be contacted 6 months to 1 year after lobectomy. Finally, 158 patients were entered into this study. All descriptive statistics were expressed as mean ± SD for continuous variables. Correlation between variables was assessed using Spearman rank correlation coefficients. A probability value of less than 0.05 was accepted as statistically significant. Statistical analysis was performed using the statistical software Statview 5.0 (SAS Inc., Cary, NC, USA). Forty-three patients underwent right upper lobectomy (RUL), 38 patients left upper lobectomy (LUL), 39 patients right lower lobectomy (RLL), and 38 patients left lower lobectomy (LLL). Patient characteristics are shown in Table 1. Patients’ characteristics Table 2 shows percentage change in pulmonary function between preoperation and postoperation. Percent change in pulmonary function between preoperation and postoperation We evaluated the correlation between a preoperative FVC or FVC% of predicted and percentage change in FVC after lobectomy (Table 3). There were no significant relationships between these variables in RUL, RLL, or LLL group. In contrast, there were significantly negative relationships between these variables in LUL group (r = −0.579, p = 0.0001, and r = −0.526, p = 0.0006, respectively). Figs. 1 and 22 show the correlation between a preoperative FVC% of predicted and percentage change in FVC in RUL and LUL groups, respectively. In LUL group, patients with a higher preoperative FVC% of predicted had a more adverse percentage change in FVC after surgery (Fig. 2). Correlation between preoperative pulmonary function and percentage change in pulmonary function after lobectomy and their correlation coefficients Correlation between preoperative FVC% of predicted and percentage change in FVC in RUL group. The bold line is the line of best fit by linear regression. Percentage change in FVC = −0.46 − 0.84 × FVC% of predicted; R2 = 0.02, r = −0.142, p = 0.3621. Correlation between preoperative FVC% of predicted and percentage change in FVC in LUL group. The bold line is the line of best fit by linear regression. Percentage change in FVC = 22.6 − 0.4 × FVC% of predicted; R2 = 0.267, r = −0.526, p = 0.0006. In addition, we also evaluated the correlation between a preoperative FEV1.0 or FEV1.0% of predicted and percentage change in FEV1.0 (Table 3). There were no significant relationships between these variables in RLL or LLL groups. In contrast, there were significant negative relationships between these variables in RUL group (r = −0.702, p < 0.0001 and r = −0.667, p < 0.0001, respectively) and LUL group (r = −0.730, p < 0.0001 and r = −0.712, p < 0.0001, respectively). Figs. 3 and 44 show the correlation between preoperative FEV1.0% of predicted and percentage change in FEV1.0 in RUL and LUL groups, respectively. In RUL and LUL groups, patients with a higher preoperative FEV1.0% of predicted had a more adverse percentage change in FEV1.0 after surgery (Figs. 3 and 4). In addition, all 13 patients with a preoperative FEV1.0% of predicted <60% in RUL and LUL groups had an increase in FEV1.0 postoperatively (Figs. 3 and 4). Patients with a lower preoperative FEV1.0% of predicted had a greater ‘volume reduction effect’ with an increase in FEV1.0 after upper lobectomy. Correlation between preoperative FEV1.0% of predicted and percentage change in FEV1.0. The bold line is the line of best fit by linear regression in RUL group. Percentage change in FEV1.0 = 28.3 − 0.4 × FEV1.0% of predicted; R2 = 0.445, r = −0.667, p < 0.0001. Correlation between preoperative FEV1.0% of predicted and percentage change in FEV1.0. The bold line is the line of best fit by linear regression in LUL group. Percentage change in FEV1.0 = 29.5 − 0.4 × FEV1.0% of predicted; R2 = 0.507, r = −0.712, p < 0.0001. An estimated 20% of patients with lung cancer have pulmonary dysfunction sufficiently severe to be considered inoperable by conventional criteria [13,14]. Lung volume reduction surgery has improved lung function in patients with pulmonary emphysema by resection of relatively functionless emphysematous lung [1–5]. Experience with LVRS suggested that a predicted postoperative FEV1.0 may be underestimated after lobectomy in patients with lung cancer and emphysema [6–11]. Moreover, COPD patients with lower forced expiratory volumes in 1 s (FEV1.0) might have less pulmonary function loss after lobectomy [8,9]. Epidemiologic studies suggest that 90% of patients with lung cancer have some signs and symptoms of chronic obstructive pulmonary disease [15]. CT scanning is undoubtedly the most sensitive method to diagnose emphysema [16]. We commonly find that patients with lung cancer have emphysematous changes in the preoperative CT scan. As most of the patients with lung cancer had more or less emphysematous changes [12], we hypothesized that lobectomy would to some extent provide the same volume reduction effects as LVRS in patients without COPD on the pulmonary function test. In RUL and LUL groups, patients with a higher preoperative FEV1.0% of predicted had a greater decrease in percentage change in FEV1.0 after surgery. From the standpoint of the percentage change in FEV1.0 after surgery, upper lobectomy but not lower lobectomy might have a volume reduction effect even in patients without COPD on the pulmonary function test. Patients with a lower preoperative FEV1.0 would have a greater ‘volume reduction effect’ after upper lobectomy. Recent studies reported that, in patients with predominantly upper lobe emphysema, as compared with predominantly non-upper lobe emphysema, LVRS offered a greater chance for improvement in pulmonary function [3–5]. We suggested that lobectomy would have the effect of both loss and gain on pulmonary function caused by resection of normal lung tissue and emphysematous lung tissue, respectively. By resection of emphysematous lung tissue, upper lobectomy would especially have the same good effect as LVRS in predominantly upper lobe emphysema. So, this hypothesis would explain to us why upper lobectomy might have a volume reduction effect even in patients without COPD on the pulmonary function test. First, Boushy et al. [17] reported that a decrease in FEV1.0 after lung resection was inversely related to the preoperative FEV1.0% of predicted, and that more normal patients had a greater decrease in FEV1.0. Pierce et al. [18] have shown that there was a significant relationship between the percentage change in FEV1.0 after lung resection and the baseline predicted FEV1.0%, indicating that functional loss is proportionately less severe in patients with poorer baseline function. Recently, some authors evaluated the FEV1.0 and FVC after lobectomy in patients with emphysema [8–11]. Korst et al. [8] reported that patients with a very low preoperative FEV1.0 and FEV1.0 to FVC ratio were less likely to reduce FEV1.0 after lobectomy, and might actually improve it. However, their severely obstructive patients were equally likely to experience a loss of FVC after lobectomy [8]. After LVRS, both FEV1.0 and FVC increase [1–5]. Korst et al. [8] suggested that a loss of FVC after lobectomy in their patients with severe emphysema was caused by resection of some functioning lung tissue, and if only non-functioning lung was removed, FVC should increase, as it does in patients undergoing LVRS. In the present study, patients with a higher preoperative FVC% of predicted in only LUL group had a greater decrease in percentage change in FVC. Why would only LUL have a volume reduction effect, even in FVC, when this was not seen in RUL? We suggest that upper lobectomy would have a greater effect of volume reduction on pulmonary function by resection of emphysematous lung tissue. Upper lobectomy would have a volume reduction effect on both FEV1.0 and FVC. However, as RUL had less loss of lung volume as compared with LUL, FVC in RUL would recover 6 months to 1 year after surgery in patients with good preoperative pulmonary function with a higher preoperative FVC. Similarly, we commonly find that, right middle lobectomy, which has little loss of lung volume, is associated with almost no change in pulmonary function. In the present study, we demonstrated that upper lobectomy might have a volume reduction effect.