Computed tomography appearances of local recurrence after stereotactic body radiation therapy for stage I non-small-cell lung carcinoma

The aim of this study was to characterize computed tomography (CT) manifestations of local recurrence after stereotactic body radiation therapy (SBRT) for stage I non-small-cell lung cancer (NSCLC). A total of 27 stage I NSCLC patients who were treated with SBRT, including 5 patients with local recurrence, were retrospectively analyzed for serial CT examinations. A bulging margin appeared in 4 of the 5 cases (80%) with local recurrence and 1 of 22 cases (5%) without local recurrence. Air bronchograms were seen in 3 of 5 cases with local recurrence and 21 of 22 cases without local recurrence, but they subsequently disappeared in all 3 cases (100%) with local recurrence and in 4 of the 21 cases (19%) without local recurrence. Ipsilateral pleural effusion was observed in all 5 cases (100%) with local recurrence and in 5 of 22 cases (22%) without local recurrence. The opacity increased in size even after 12 months from the completion of SBRT in cases with local recurrence, whereas it decreased or did not change in size in cases without recurrence. Local recurrence should be suspected on CT when there was (1) a bulging margin, (2) disappearance of air bronchograms, (3) appearance of pleural effusion, or (4) increase in the abnormal opacity after 12 months.