Trimodality therapy of malignant pleural mesothelioma with helical tomotherapy

Abstract

M PM is an aggressive tumor that originates from the pleural surfaces and associated with asbestos exposure [1]. In recent studies some tumor suppressor genes, such as BAF-1, have been identified as factors in mesothelioma carcinogenesis [2].MPM is divided into 3 histopathological subgroups by WHO, which differ from each other in terms of prognosis: epithelioid, sarcomatoid, and biphasic. Epithelioid is the most common histopathological type with the best prognostic features, with a median survival of 14 months. Survival times of biphasic and sarcomatoid types were reported as 10 and 4 months, respectively [3].MPM treatment includes different approaches such as surgery, radiotherapy, and chemotherapy. Two surgical approaches are available: gross tumor resection and radical removal of visible disease with tissues, or conservative approaches such as tissue sparing and debulking. Extra-pleural pneumonectomy (EPP) is a radical ap- ABSTRACT OBJECTIVE:The purpose of this study was to determine the efficacy and tolerability of hemithoracic radiotherapy implemented with helical tomotherapy (HTT) in malignant pleural mesothelioma (MPM) patients. METHODS:Between October 2018 and December 2020, data from 11 MPM patients who received trimodality therapy, including lung-sparing surgery (pleurectomy-decortication, P/D), adjuvant chemotherapy (cisplatin+ pemetrexed), and radiotherapy, were retrospectively reviewed. HTT was used to deliver a total of 30 Gy, 50-54 Gy or 59.4-60 Gy to R2 disease with 1.8-2 Gy daily doses. Descriptive data are presented in number (percentage) or median (minimum-maximum). The Kaplan-Meier method was used to calculate survival data. In patients with toxicities, the risk organ doses were compared using the Mann-Whitney U test. RESULTS:The median follow-up was 20.5 (12-30) months. Two-year local control, disease-free, and overall survival rates were 48.5%, 49%, and 77.9%, respectively. The median prescribed dose for planning target volume (PTV) was 50.4±8.7 (30-60) Gy. Mean dose (D mean ) of total lung was 19.9±6 (10.4-26) Gy; the V20 (%) of ipsilateral and contralateral lungs were 89.±11.2 (62.7-100) and 0.7±2.1 (0.49-5.9), respectively. Esophageal D mean and maximum doses (D max ) were found as 21. 7±8.4 (7.4-34) and 53.1±10.4 (25.4-64.4) Gy, respectively. V30 (%) and Dmean of heart were 22.3%±13.4% (3.9-47) and 21±5.7 (10.8-29.3) Gy, respectively. D max of medulla spinalis (MS) was 38.6± 1.3 (13.7-48) Gy. Grade 1-2 radiation pneumonitis (RP) developed in 4 (36.4%) and esophagitis in 2 (18.2%) patients. RP was found to be associated with MS and esophageal doses (p<0.05). Myelitis was diagnosed in 1 (9.1%) patient (MS D max : 29 Gy).CONCLUSION: HTT can be used as part of trimodality therapy for MPM patients with acceptable toxicities. MS and esophageal doses should be considered for radiation pneumonitis risk, and new dose constraints for these organs should be defined.