Patterns of Postoperative Changes in Lung Volume and Perfusion Assessed by Dual-Energy CT: Comparison of Lobectomy and Limited Resection

Abstract

Background: Pulmonary function tests (PFTs) and perfusion scintigraphy have limited utility for evaluating postoperative changes in regional pulmonary function after lung cancer resection surgery. Objective: To compare postoperative changes in lung volume and perfusion, assessed by dual-energy CT (DECT), between patients undergoing lung cancer surgical resection by lobectomy and limited resection, and to assess such changes' associations with the resected tumor's lobar location. Methods: This study entailed a retrospective post-hoc analysis of a prospective study that enrolled patients awaiting lung cancer resection surgery between March 2019 and February 2020. Eighty-one patients (38 men, 43 women; mean age, 60.5±8.9 years; lobectomy in 43, limited resection in 38) were included. Patients underwent thoracic DECT and PFT evaluation preoperatively and 6 months postoperatively. Pulmonary lobes were segmented. Lobar volume and perfusion ratios (both relative to whole-lung values) were computed. Perfusion measures reflected DECT-derived iodine content. Patients completed 6-month postoperative quality-of-life (QOL) questionnaires. Results: Patients undergoing lobectomy, versus limited resection, exhibited greater increases in lung volume ratio of ipsilateral nonresected lobe(s) (42.3±24.2% vs 22.9±13.2%, p<.001) and of contralateral lung (14.6±14.0% vs 6.4±6.9%, p=.002), and greater increases in lung perfusion ratio of ipsilateral nonresected lobe(s) (39.9±20.7% vs 22.8±17.8%, p<.001) and of contralateral lung (20.9±9.4% vs 4.3±5.6%, p<.001). In patients with right lower lobe tumors, largest postoperative increases in lung volume ratio were in right middle lobe in those undergoing lobectomy (44.1±21.0%) and limited resection (24.6±14.5%), whereas largest postoperative increase in lung perfusion ratio was in left lower lobe in those undergoing lobectomy (53.9±8.6%) and in right middle lobe in those undergoing limited resection (32.5±24.1%). Otherwise, largest volume and perfusion ratio increases occurred in ipsilateral nonresected lobes (vs contralateral lobes) regardless of operative approach and lobar location. Lung volume and perfusion ratio changes in ipsilateral lobe(s) and contralateral lung showed weak correlations with certain QOL scores [e.g., role functioning: ρ=0.234-0.279 (volume); -0.233 to -0.284 (perfusion)]. Conclusion: DECT depicts patterns of lung volume and perfusion changes after lung cancer surgery, depending on surgical approach (lobectomy vs limited resection) and tumor lobar location. Clinical Impact: DECT-derived metrics can help understand variable physiologic impacts of lung cancer resection surgeries.