Assessment of delays in diagnosis of lung cancer in interstitial lung disease.

Abstract

Objectives: To evaluate diagnostic delays in lung cancer among patients with interstitial lung disease (ILD), assess tumor characteristics and outcomes, and identify radiologic factors contributing to missed or delayed detection.

Materials and methods: In this retrospective study, 54 ILD patients with concurrent lung cancer from two tertiary ILD referral centers were reviewed. A panel of four thoracic radiologists determined the earliest callable date-when the majority would have raised concern about a nodule-compared to the date of first clinical suspicion. Tumor size, morphology, staging, growth rate (volume doubling time), treatment regimens, and survival were analyzed. For delayed cases, radiologic causes of missed detection were categorized by consensus.

Results: Diagnostic delays occurred in 50% of cases (27/54), with a mean delay of 3.18 years (IQR: 0.94-4.51). Delayed cases showed significantly slower tumor growth (mean volume doubling time: 1.42 vs. 0.22 years, p < 0.0001). The most common radiologic factors contributing to missed detection were obscuration by fibrosis, ground-glass opacity, or bronchovascular bundles (63%), misinterpretation as infection or exacerbation (15%), minimal interval growth (11%), and invisibility on CT (15%). Tumor size, morphology, stage, and histologic subtype-most commonly adenocarcinoma (56%)-were similar between groups. No significant difference in survival was observed between delayed and non-delayed cases (χ² = 0.4, p = 0.5).

Conclusion: Half of the lung cancer cases in ILD patients were diagnosed with significant delay, primarily due to parenchymal masking and subtle imaging findings, rather than biologically aggressive disease. Despite delays, survival outcomes and tumor characteristics did not differ significantly, suggesting a less aggressive tumor phenotype in delayed cases.

Key points: Question To evaluate diagnostic delays in lung cancer among patients with interstitial lung disease (ILD), assess tumor characteristics and outcomes, and identify radiologic factors contributing to missed or delayed detection. Findings Half of lung cancer cases in ILD patients had diagnostic delays, mainly due to parenchymal masking. Delayed cases showed slower growth but no survival difference; tumor size and histology were indifferent. Clinical relevance This study shows that lung cancer diagnosis is often delayed in ILD patients (avg. > 3 years). Clinicians should stay alert for malignancy in peripheral fibrotic regions with slow-growing nodules. Despite no clear survival impact, future work should assess the risks and benefits of earlier detection.