Introduction: A rare but serious complication of epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI) therapy is a lung injury syndrome commonly referred to as a drug-induced interstitial lung disease (ILD). It has a typical clinical presentation of rapidly progressive acute or subacute dyspnea and a histopathology of diffuse alveolar damage (DAD). The incidence, severity, and risk factors for EGFR TKI-induced ILD remain poorly understood. Whether concurrent chemotherapy increases its risk is also unclear. The primary focus of this blinded review was to determine the incidence of ILD leading to death in 1059 TRIBUTE patients randomized to chemotherapy plus erlotinib or placebo.
Methods: All fatal serious adverse events (SAEs) were reviewed by an independent three-person panel composed of a medical oncologist, radiologist, and pulmonologist not associated with the study and without knowledge of treatment assignment. Fatal respiratory SAEs were identified and assigned to one of four potential attributions: progressive cancer, concurrent illness, drug-induced ILD, or other toxicities not related to ILD. Each panel member first made an independent assignation; then each case was discussed jointly. If needed, consensus was reached by vote.
Results: Fatal SAEs were reported in 80 of 1059 patients (7.6%): 53 of 526 patients on erlotinib (10.1%) and 27 of 533 on placebo (5.1%) (p < 0.05). Consensus assignation for 41 fatal respiratory SAEs was as follows: cancer, 18 (44%); concurrent illness, 15 (37%); other toxicities not related to ILD, five (12%); ILD, three (7%). All three ILD cases occurred in the erlotinib arm (3/526; 0.6%). The one biopsy-confirmed case of ILD revealed bronchiolitis obliterans organizing pneumonia, a histopathologic finding that has not previously been reported. All three cases of fatal ILD had a typical clinical presentation of acute or subacute onset of dyspnea with rapid progression to respiratory failure.
Conclusions: This independent blinded analysis of the TRIBUTE study identified fatal ILD in 0.6% of cases treated with the combination of erlotinib plus chemotherapy, possibly higher than previous reports of EGFR TKIs alone in the non-Japanese population. Fatal ILD alone does not fully account for the imbalance in fatal SAEs observed in TRIBUTE. EGFR TKI-induced fatal ILD typically presents with acute or subacute dyspnea with rapid progression and a typical histopathology of diffuse alveolar damage both consistent with the acute respiratory distress syndrome, but can also be associated with a histopathology of bronchiolitis obliterans organizing pneumonia. Further studies designed to better understand the underlying pathophysiology and risk factors for ILD are needed.