An analysis of residual lung volume changes after segmentectomy based on three-dimensional computed tomography

Abstract

Background: Based on the results of JCOG0802 and CALGB studies, segmentectomy has considered to be a standard procedure for early-stage non-small cell lung cancer (NSCLC). After lobectomy, the residual cavity is filled with mediastinal and diaphragmatic deviations, and compensatory volume changes are present in the residual lungs. In this study, we examined the efficacy of segmentectomy, a surgical procedure, by focusing on its impact on postoperative lung volume and function.

Methods: We enrolled 77 patients who underwent segmentectomy as their initial surgical procedure, excluding those with additional lung resections and those who lacked postoperative computed tomography imaging. The predicted residual volume (mL) was defined as the total lung volume before surgery minus the volume of the resected area. Using the predicted residual volume (mL) and postoperative total lung volume (mL), we calculated the rate of postoperative lung volume increase [(postoperative total lung volume/predicted residual volume) × 100] (%). We also classified 52 cases with a rate of postoperative lung volume increase of ≥100% into a compensatory group, while those with a rate of <100% were classified into a non-compensatory group.

Results: The average postoperative lung volume increase was 104.6% among 77 cases. Age ≥65 years, pack year index ≥27.5, ≥3 resected segments, and use of electrocautery for intersegmental plane division were significantly associated with compensatory group classification. In 20 compensatory cases with preoperative and postoperative pulmonary function tests, postoperative vital capacity and forced expiratory volume in one second values exceeded the preoperative predictions. This study further examined the areas responsible for postoperative compensatory lung volume increase. In the compensatory group, significant expansion was observed in the ipsilateral lobes, excluding the resected segment and contralateral lung, while no significant changes were noted in the volume of the lobe, including the resected segment. Conversely, the non-compensatory group showed a significant volume decrease in the resected lobe, but no significant increase in other areas.

Conclusions: This study emphasizes the importance of preserving lung segments in segmentectomy. The study demonstrates extensive compensatory volume changes in the ipsilateral lung and contralateral lung. There was no significant volume decrease in any residual segment. This underlines the potential of segmentectomy to maintain lung function and expand treatment options post-surgery. In addition, the compensated group included patients with a lower pack-year index and younger patients. These results suggest that postoperative compensatory lung expansion includes not only hyperinflation of the remaining lung, but also an increase in the functional lung parenchyma.

Keywords: Segmentectomy; lung cancer; lung volume change; sublobar resection; three-dimensional computed tomography (3D-CT).

Figure 1

Three categories of residual lungs to examine the details of postoperative compensatory lung expansion. The residual lungs were divided into three parts for detailed comparison: (A) the volume of the lobe including the resected segment (preservation segment), (B) the total volume of the ipsilateral lobes excluding the resected segment, and (C) the total volume of the contralateral lung.

Figure 2

Dynamics of the residual lungs in the thoracic cavity. (A) Image of the thoracic cavity immediately after segmentectomy. An example of left upper division segmentectomy is shown. (B) Image of the thoracic cavity one year after segmentectomy. The following dynamic lung expansion (blue arrows) and shift occurred (red dotted arrows): (I) the volume of the lobe, including the resected segment, is preserved, and this lobe shifts to the cranial side of the thoracic cavity; (II) the significant expansion of the total volume of the ipsilateral lobes, excluding the resected segment, shifted to the cranial side following the shift of the resected segment; and (III) the significant expansion of the total volume of the contralateral lung, which shifted to the ipsilateral side following the decrease in the total lung volume of the ipsilateral side.