P2.06-02 Feasibility of Intensity Modulated Radiotherapy After Pleurectomy/Decortication for Malignant Pleural Mesothelioma Patients

Abstract

Treatment strategies for patients with malignant pleural mesothelioma (MPM) include pneumectomy followed by radiation with considerable efficacy, although post-surgical morbidity and mortality are frequent. Recently, more conservative surgical approaches have been implemented, including Pleurectomy/Decortication (P/D), which spares the lung tissue while removing the malignant pleura and visible tumor. Although this approach significantly reduces surgical morbidity, it poses a challenge for post-surgical radiotherapy, as the risk of developing radiation pneumonitis is high. In this feasibility study we evaluated the loco-regional control and toxicity profile in patients with MPM treated with induction chemotherapy followed by P/C and Intensity Modulated Radiotherapy (IMRT) to the entire thoracic cavity. Patients with MPM treated from October 2011 to February 2014 were screened for inclusion. All patients underwent 4 cycles of induction chemotherapy with cisplatin/gemcitabine or cisplatin/pemetrexed without progression followed by P/D. Thereafter, patients received IMRT to the thoracic cavity (50.4-54 Gy in 28-30 fractions), treated with 9-11 non-coplanar fields. A total of 20 patients were screened for inclusion, from these, 13 patients were included in the final analysis. The median age was 61.3 ±10.3 years; 69.2% (9/13) were classified as low risk according to the European Organization for Research and Treatment of Cancer prognostic group. From the 13 patients, 12 (92.3%) had a histological diagnosis of epithelioid mesothelioma, while one patient (7.7%) presented with a sarcomatoid histology. Partial response to chemotherapy was observed in 61.5% (8/13) and stable disease in 38.5% (5/13). After P/D, only 23% (3/13) had residual macroscopic disease. The median follow-up was 23.6 months (7.5-44.7). Nine patients had recurrence or progression (6 distant [67%] and 3 loco-regional recurrences [33%]). 2-year Progression Free Survival was 31.3% (95%CI [8.72-57.51]). Only one patient died due to hepatic metastases. Any grade Pneumonitis was reported in 69.2% (9/13), however only 22.2% (n=2) of patients presented grade ≥3 pneumonitis. The V5 of the contralateral lung was above 70% and the V20 of the total lung was 45% in these patients. No IMRT-related deaths were observed throughout the study. Results from this pilot study show that it is feasible to administer IMRT to patients who have undergone P/D while maintaining an adequate toxicity profile. In our study pulmonary toxicity was frequent; however there was only one event of grade 4 pneumonitis, meanwhile the loco-regional control using this treatment modality shows great promise. However, a larger study with a more robust sample size is required to draw strong conclusions.