Impact of interstitial lung disease gender-age-physiology index in surgically treated lung cancer.

Background: The postoperative prognosis of patients with interstitial lung disease (ILD) and lung cancer is poor. Recently, the ILD-gender-age-physiology (GAP) index was identified as a clinical prognostic factor for patients with ILD. This study investigated the ILD-GAP index and oncological factors regarding postoperative outcomes.

Methods: We retrospectively reviewed 87 lung cancer patients with comorbid ILD who underwent curative resection at our institution between April 2005 and December 2019. Short-term postoperative outcomes and overall survival (OS) based on the ILD-GAP index were examined. OS rates after surgery were calculated using the Kaplan-Meier method, and group differences were analyzed using the Log-Rank test. Univariate and multivariate analyses for OS were performed using the Cox regression model.

Results: Multivariate analyses revealed ILD-GAP index ≥ 4 [Hazard ratio, 3.349; 95% confidence interval 1.375-8.155; P = 0.008] as a factor associated with OS. In the ILD-GAP index ≥ 4 group, no deaths occurred from primary lung cancer, with respiratory-related deaths being the most common, and exacerbation of ILD was more frequent (P = 0.007). Regarding perioperative results, a significant difference was observed in 90-day mortality (2.7% vs. 23.0% [P = 0.022]), and more patients required home oxygen therapy (14.9% vs. 69.2% [P < 0.001]) in the ILD-GAP index ≥ 4 group.

Conclusions: An ILD-GAP index ≥ 4 indicated a poor prognostic factor for patients with surgically treated lung cancer. Careful consideration of surgical indications is essential for patients with an ILD-GAP index ≥ 4.