The initial 152 reported patients with NSCLC in Japan who had experienced adverse events involving the lungs while receiving treatment with gefitinib were included in the first assessment of the algorithm. Of these, 135 were included in the second assessment because radiological examinations, including 47 with CT imaging, were available. Approximately 20% of these patients (23 out of 135) were considered by the expert panel not to have drug-associated ILD, highlighting the difficulty in diagnosing drug-associated ILD in patients with NSCLC.