Does selective pleural irradiation of malignant pleural mesothelioma allow radiation dose escalation?

Purpose To investigate if selective compared to elective pleural irradiation of malignant pleural mesothelioma (MPM) can allow dose escalation. Patients and methods Twelve consecutive stage I-IV MPM patients (6 consecutive left-sided and 6 consecutive right-sided) were retrospectively identified from a prospective institutional database and included. In all patients, the staging computed tomography and the staging magnetic resonance imaging (MRI) were used for gross tumor volume (GTV) definition. The patients had not received chemotherapy. An MRI-based pleural GTV was contoured and a planning target volume (PTV) was generated. Two sets of PTVs were generated for each patient: (1) a “selective” PTV (S-PTV), originating from a 5-mm isotropic expansion from the GTV, and (2) an “elective” PTV (E-PTV), originating from a 5-mm isotropic expansion from the whole ipsilateral pleural space. Two sets of volumetric modulated arc therapy (VMAT) treatment plans were generated for each patient: a “selective” pleural irradiation plan (SPI plan) and an “elective” pleural irradiation plan (EPI plan). Results In the SPI plans, the median dose to the S-PTV was 53.6 Gy (SD: 5.4, range: 41–63.6 Gy). In 4/12 patients it was possible to escalate the dose to the S-PTV to > 58 Gy. In the EPI plans, the median dose to the E-PTV was 48.6 Gy (SD: 5.8, range: 38.5–58.7), with a median dose to the S-PTV of 49 Gy (SD: 6, range: 38.6–59.5 Gy). No significant dose escalation was achievable. Conclusion The omission of elective irradiation of the whole ipsilateral pleural space allows dose escalation from 49 Gy to more than 58 Gy in 4/12 chemo-naive MPM patients. This strategy may form the basis for non-surgical radical combined modality treatment of MPM. [ABSTRACT FROM AUTHOR]