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

Our plain-English summary of Initial clinical experience treating patients with palliative radiotherapy for malignant pleural mesothelioma on the HalcyonTM linear accelerator, by A.R. Barsky, M.M. Kim, R. Maxwell, et al (Annals of Palliative Medicine, 2020).

The study

• Authors: A.R. Barsky, M.M. Kim, R. Maxwell, A. Mendes, C.M. Wright, E.J. Anstadt, S. McNulty, L. Dong, J.M. Metz, S.J. Feigenberg, T. Li, K.A. Cengel
• Journal: Annals of Palliative Medicine
• Published: 2020;9(5):2903-2912
• Cited by: 2 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

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, HalcyonTM (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 HalcyonTM to deliver palliative RT for patients with MPM.

Methods: We retrospectively assessed consecutive patients with MPM who received thoracic RT on HalcyonTM. 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 HalcyonTM 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 HalcyonTM, 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 HalcyonTM can provide patients with MPM quick and safe tumor-related symptom relief, even in a frail, elderly population.

In plain English

This was a retrospective case series from one university hospital. It described four consecutive patients with stage IV malignant pleural mesothelioma who were treated between January 2017 and January 2020. Each received palliative (symptom-relieving) chest radiotherapy on the Halcyon linear accelerator, a newer radiotherapy machine. The study did not examine asbestos exposure. The patients' median age was 81. Two were treated for pain requiring narcotics, one for difficulty swallowing and one for breathlessness, with doses from 20 to 45 Gy. At a median follow-up of 2.2 months, three patients' symptoms improved and one patient's stayed stable. Both pain patients reported complete pain resolution at the treated sites and stopped narcotics within 1 to 2 weeks. No patient had grade 3 or higher acute (short-term) side effects. One had grade 2 fatigue and one had grade 2 cough. Mean beam-on time was 1.6 minutes. All four patients died of disease progression outside the treated areas. The authors concluded that palliative radiotherapy on this machine can give quick and safe symptom relief, while noting the small sample and short follow-up.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Retrospective case series (review of electronic medical records) at a single institution
• Who was studied: Four consecutive patients with stage IV malignant pleural mesothelioma, median age 81 (range 75 to 83), treated at the Hospital of the University of Pennsylvania between 1/2017 and 1/2020. Histology was epithelioid in 2, biphasic in 1 and sarcomatoid in 1. Median ECOG performance status was 2.
• Exposure: No asbestos exposure was studied. The treatment studied was palliative thoracic radiotherapy (VMAT) on the Halcyon linear accelerator, in 3 to 4 Gy fractions to total doses of 20 to 45 Gy. Three of the four patients also received systemic therapy at the same time as radiotherapy.
• Main results:
  • Symptoms were treated for narcotic-requiring pain (2 of 4), dysphagia (1 of 4) and dyspnea (1 of 4).
  • At a median follow-up of 2.2 months (range 1.6 to 7.1 months), symptoms improved in 3 of 4 patients and stayed stable in 1 of 4.
  • Both patients treated for chest wall pain reported complete resolution of pain at the irradiated sites and stopped narcotics within 1 to 2 weeks after radiotherapy.
  • All four patients died of disease progression outside the irradiated areas.
  • No patient had grade 3 or higher acute side effects. Grade 2 fatigue occurred in 1 of 4 patients and grade 2 cough in 1 of 4. Grade 1 effects included dyspnea in 4 of 4, fatigue in 3 of 4, cough in 2 of 4 and nausea in 2 of 4.
  • All 4 plans met target coverage constraints. Three of 4 met all organ-at-risk constraints. One plan gave a maximum esophageal dose of 16.2 Gy against a 16 Gy constraint.
  • Across all patients, the mean beam-on time was 1.6 plus or minus 0.2 min and the mean treatment time was 1.8 plus or minus 0.2 min. The approximated total room usage time was 9.8 plus or minus 0.2 min. The mean 3D couch (setup) correction was 0.67 plus or minus 0.15 cm.
• The authors' conclusion: The authors concluded that, in this initial experience, palliative radiotherapy on Halcyon provided symptom palliation with minimal toxicity, acceptable dosimetry, and setup corrections and treatment times that compared favorably with other published reports. They stated it can give patients with malignant pleural mesothelioma quick and safe tumor-related symptom relief, even in a frail, elderly population.
• Limitations the authors state:
  • The small sample size may limit how far the results can be generalized.
  • Follow-up was short, and disease or symptoms might recur with longer follow-up in patients who survive longer.
  • Total room time was not measured. It was estimated from a breast cancer study whose patients had better performance status, so the true room times may be longer.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Mesothelioma.

Medical terms in this study, explained in our Lexicon: Palliative Care, Pleural Mesothelioma, Dysphagia, Dyspnea, Pleura, Hilum, Mediastinum, Systemic Therapy.

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