Clinical factors associated with unilateral upper lung field pulmonary fibrosis after oesophagectomy: a single-centre retrospective study using longitudinal 3D-CT analysis

Unilateral upper lung field pulmonary fibrosis (UUPF) is a rare complication of thoracotomy that resembles pleuroparenchymal fibroelastosis. However, the clinical course and risk factors after oesophagectomy remain unclear. Thus, we aimed to examine the cumulative incidence of UUPF after oesophagectomy, identify factors associated with UUPF development, and evaluate volumetric predictors of UUPF development and subsequent volumetric decline. We retrospectively analysed data from 443 patients who underwent oesophagectomy. Lung volumes were quantified using three-dimensional computed tomography (3D-CT) at baseline and annually for 5 years postoperatively. Multivariable Firth penalised logistic regression analysis was used to identify factors independently associated with UUPF development during the entire follow-up period. Receiver operating characteristic analysis was used to identify volume-based predictors of subsequent UUPF development. The Mann–Whitney U test was used to assess the association between right upper lobe volume decline and clinical factors. The cumulative incidences of UUPF were 1.4%, 4.7%, and 9.1% at 3, 5, and 10 years, respectively. In Firth penalised logistic regression analysis, factors associated with UUPF development included male sex, preoperative apical caps, pleural effusion at 6 months postoperatively, and postoperative gastroesophageal reflux disease (GERD), although the association with GERD was borderline and model-dependent. Among volume metrics, the right upper lobe/left lung volume ratio at 3 years had the highest predictive performance (area under the curve, 0.770), with an optimal cutoff of 75.2% (sensitivity, 88.0%; specificity, 54.2%). GERD within 3 years postoperatively was significantly associated with greater right upper lobe volume decline over 5 years postoperatively (median [95% confidence interval]: 63.2% vs. 75.0%; p = 0.041). UUPF is not uncommon after oesophagectomy, and male sex, preoperative apical caps, and pleural effusion were associated with UUPF development, whereas the association with postoperative GERD was model-dependent and borderline. Longitudinal volumetric analysis using 3D-CT is a valuable tool for early detection and monitoring of UUPF. The exploratory analysis suggested an association between postoperative GERD and greater volumetric progression of UUPF; however, this finding should be interpreted cautiously and requires validation in larger prospective studies.