Computed tomography features of local pleural recurrence in patients with malignant pleural mesothelioma treated with intensity-modulated pleural radiation therapy.

Objective: This study was conducted in order to describe the computed tomography (CT) features of local pleural recurrence in patients with malignant pleural mesothelioma undergoing intensity-modulated pleural radiation therapy (IMPRINT) as part of multimodality treatment.

Methods: In this observational study, 58 patients treated with IMPRINT between September 21, 2004, and December 1, 2014 were included. Baseline and follow-up CT scans were qualitatively assessed. On follow-up scans, pleural thickening was categorized as unchanged, decreased, or new/increased. New/increased pleural abnormality was subcategorized as diffuse smooth pleural thickening, diffuse nodular pleural thickening, focal pleural nodule, or multiple pleural nodules. To identify features more frequently present at the time of local recurrence, follow-up scans with local recurrence were matched to four control scans; exact conditional logistic regression was performed.

Results: Twenty-one (36%) patients had local pleural recurrence and 20 (34%) patients had nonpleural recurrence; 3 patients had both types of recurrence. The 1-year cumulative incidence rate of local recurrence was 27% (95% confidence interval 15, 39). On follow-up scans, three patterns of pleural abnormality were significantly associated with local recurrence: new/increased multiple pleural nodules (10 (48%) positive scans vs 0 control scans), new/increased diffuse nodular pleural thickening (7 (33%) positive scans vs 1 (1%) control scans), and new/increased focal pleural nodule (3 (14%) positive scans vs 1 (1%) control scan) (p < 0.001 for all).

Conclusions: Multiple new/increased pleural nodules are the feature most commonly present at local recurrence following IMPRINT; however, any pattern of increased nodular pleural thickening is suspicious.

Key Points: • In patients with mesothelioma receiving intensity-modulated pleural radiation as part of multimodality therapy, increasing multiple pleural nodules is the computed tomography feature most commonly present at local recurrence. • In these patients, any CT pattern of increased nodular pleural thickening should be considered suspicious for local recurrence. • The most common sites of nonpleural recurrence were lung parenchyma, thoracic lymph nodes, and peritoneum.