Initial clinical experience treating patients with palliative radiotherapy for malignant pleural mesothelioma on the HalcyonTM linear accelerator

Abstract

Background: Radiation therapy (RT) can provide effective symptomatic palliation in patients with malignant pleural mesothelioma (MPM). Advances in RT technology, including intensity-modulated RT (IMRT) and volumetric-modulated arc therapy (VMAT), have improved treatment conformality, potentially improving the therapeutic ratio of RT. A novel 6-MV flattening-filter-free O-ring linear accelerator, Halcyon TM (Varian Medical Systems, Palo Alto, CA, USA), was built to provide such advanced therapies, while possibly reducing treatment time. Here, we report the initial clinical experience using Halcyon TM to deliver palliative RT for patients with MPM. Methods: We retrospectively assessed consecutive patients with MPM who received thoracic RT on Halcyon TM . Their electronic medical records were reviewed for clinical, RT planning, treatment timing, and image-guidance RT (IGRT) data.Results: Four patients with metastatic MPM received palliative RT on Halcyon TM between 1/2017-1/2020 for severe pain (50%), dysphagia (25%), or dyspnea (25%). Targets included a combination of pleura, chest wall, lung, hilum, and mediastinum, with patient-specific dose and fractionation regimens ranging from 20-45 Gy in 5-15 fractions, and 75% of patients receiving concurrent systemic therapy. Pre-specified target and organ-at-risk constraints were met for nearly all plans. At a median follow-up of 2.2 months (range, 1.6-7.1 months), all patients experienced either improved (75%) or stable (25%) tumor-related symptoms following palliative RT. The mean 3D vector couch correction was 0.67±0.15 cm. The mean beam-on, treatment (beam-on plus cone-beam computed tomography times), and approximated total room usage times were 1.6±0.2, 1.8±0.2, and 9.8±0.2 min, respectively. Grade 2 fatigue and cough occurred in 25% and 25% of patients, and no patients experienced Grade ≥3 toxicity. Conclusions: In this initial clinical experience treating patients with palliative RT for MPM on Halcyon TM , treatment provided symptom palliation and local control across multiple palliative scenarios, with minimal toxicity, acceptable dosimetry, and setup corrections and treatment times that compared favorably with other published experiences of MPM RT. Palliative RT on Halcyon TM can provide patients with MPM quick and safe tumor-related symptom relief, even in a frail, elderly population.

Initial Clinical Experience Treating Patients With Lung Cancer on a 6MV-Flattening-Filter-Free O-Ring Linear Accelerator

“…While prior reports have shown short treatment times and high throughput for patients treated on a 6X-FFF ORL for breast cancer [20], gynecologic cancers [12], and MPM [21], our report is the first clinical report of TRT using this linac for LC, and showed similar results. Quick treatments may improve the patient experience, as treatment tables are often uncomfortable, and maintaining immobility for prolonged periods of time may be difficult, particularly in patients with LC, many of whom may be elderly, frail, and/or have underlying pulmonary and cardiovascular co-morbidities.…”

“…Published reports of 6X-FFF O-ring linacs (ORL) are largely limited to pre-clinical planning studies, and have demonstrated similar plan quality with faster calculated treatment times for 6X-FFF ORLs versus CALs [14][15][16][17][18][19]. Reports of the clinical use of a 6X-FFF ORL to date have been limited to breast cancer [20], gynecologic cancers [12], and malignant pleural mesothelioma (MPM) [21], and have demonstrated fast treatment times and high throughput with the 6X-FFF ORL compared to CALs, with comparable plan quality, toxicity, and early disease-control.…”

Safety and efficacy of helical tomotherapy following lung-sparing surgery in locally advanced malignant pleural mesothelioma

“…With the ongoing implementation of next-generation O‑ring linear accelerators into clinical practice, interest has increased in experiences with last-generation HT [ 26 ]. First reports on palliative HT of MPM suggest good efficacy at low toxicity [ 27 ]. Only a very small series of 10 patients [ 28 ] has previously assessed the role of IMRT HT for P/D patients, reporting an excellent toxicity profile.…”