Failure Patterns After Hemithoracic Pleural Intensity Modulated Radiation Therapy for Malignant Pleural Mesothelioma

Abstract

Purpose We have previously reported on our technique to deliver intensity-modulated radiotherapy (IMRT) to the entire pleura while attempting to spare the lung in patients with malignant pleural mesothelioma (MPM). Herein, we report a detailed pattern-of-failure analysis in patients with MPM who were unresectable or underwent pleurectomy/decortications (P/D), uniformly treated with hemithoracic pleural IMRT. Methods Sixty-seven patients with MPM were treated with definitive or adjuvant hemithoracic pleural IMRT between 11/2004 and 5/2013. Pretreatment imaging, treatment plans, and post-treatment imaging were retrospectively reviewed to determine failure location(s). Failures were categorized as in-field (within the 90% isodose line), marginal (<90% and ≥50% isodose lines), out-of-field (outside the 50% isodose line), or distant. Results The median follow-up was 24 months from diagnosis and the median time to in-field local failure from the end of radiotherapy was 10 months. Forty-three in-field local failures (64%) were found with a 1- and 2-year actuarial failure rate of 56% and 74%, respectively. For patients who underwent P/D versus those who received a partial pleurectomy or were deemed unresectable, the median time to in-field local failure was 14 months versus 6 months, with 1- and 2-year actuarial in-field local failure rates of 43% and 60% versus 66% and 83%, respectively (p=0.03). There were 13 marginal failures (19%). Five of the marginal failures (38%) were located within the costomediastinal recess. Marginal failures decreased with increasing institutional experience (P = .04). Twenty-five patients (37%) had out-of-field failures. Distant failures occurred in 32 patients (48%). Conclusion After hemithoracic pleural IMRT, local failure remains the dominant form of failure pattern. Patients treated with adjuvant hemithoracic pleural IMRT after P/D experience a significantly longer time to local and distant failure than patients treated with definitive pleural IMRT. Increasing experience and improvement in target delineation minimize the incidence of avoidable marginal failures.

Optimal gross tumor volume definition in lung-sparing intensity modulated radiotherapy for pleural mesothelioma: an in silico study

“…In all published experiences of lung-sparing IMRT in MPM, irradiation of the whole pleura has been performed [10][11][12][13][14][15][16]. The clinical target volume (CTV) consisted of the whole pleural space, contoured from the lung apex to the diaphragm insertion (T12-L2).…”

“…The clinical target volume (CTV) consisted of the whole pleural space, contoured from the lung apex to the diaphragm insertion (T12-L2). Median doses to the planning target volume ranged from 47 to 50 Gy [10][11][12][13][14][15][16]. In all cases, PET/CT was frequently (but not routinely) used to modify the CTV, with the inclusion of any FDG-avid area.…”

“…Lung-sparing intensity modulated radiation therapy (IMRT) (alone or after P/D) has been proven feasible and safe [10][11][12][13][14][15][16].…”

Malignant pleural mesothelioma: adjuvant therapy with radiation therapy

“…MSKCC updated their experience and reported on patients treated with hemithoracic pleural IMRT (22). The goal of this study was to determine the location of local failure and correlate it with characteristics such as imaging, the treatment plan, and post-treatment imaging.…”

Local and Systemic Therapies for Malignant Pleural Mesothelioma

“…The rate of in-field local failure was 64 %, with 1-and 2-year total failure rates of 56 % and 74 %, respectively. Interestingly, the authors also found that failure within the fissures was 16 %, and only 1 patient had an incisional failure despite the practice of not routinely boosting the incisional sites [56]. IMRT after pleurectomy/decortication, with the dose distribution and the dose volume histogram (bottom right).…”