A randomised trial of single-dose radiotherapy to prevent procedure tract metastasis by malignant mesothelioma

Our plain-English summary of A randomised trial of single-dose radiotherapy to prevent procedure tract metastasis by malignant mesothelioma, by S. Bydder, M. Phillips, D.J. Joseph, et al (British Journal of Cancer, 2004).

The study

• Authors: S. Bydder, M. Phillips, D.J. Joseph, F. Cameron, N.A. Spry, Y. DeMelker, A.W. Musk
• Journal: British Journal of Cancer
• Published: 2004;91(1):9-10
• Type of article: Randomized trial
• Cited by: 110 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

A single 9-MeV electron treatment, following invasive thoracic procedures in patients with malignant pleural mesothelioma, was examined. In all, 58 sites were randomised to prophylactic radiotherapy or not. There was no statistically significant difference in tract metastasis. A single 10-Gy treatment with 9-MeV electrons appears ineffective.

In plain English

This short report described a randomised trial in Perth, Australia, in people with malignant pleural mesothelioma. It tested whether one chest wall radiotherapy treatment could stop the cancer growing along the track left by a chest procedure (a drain or thoracoscopy, an Abrams needle, or a fine needle aspiration). Between December 1997 and July 2003, 58 procedure sites from 43 patients were randomly assigned. Of these, 28 sites were assigned to one 10 Gy dose using 9-MeV electrons and 30 to no preventive treatment, though one control-arm patient was given the radiotherapy at the patient's request. Tract metastases occurred at three control-arm sites (10%) and two radiotherapy-arm sites (7%). This difference was not statistically significant. Side effects were mild, and median survival was 8.7 months. The study did not examine asbestos exposure. The authors concluded that this single dose did not appear effective. Using a radiation model, they estimated its equivalent dose at about 40% of reported three-treatment schedules. They also noted that control-arm tract metastases were low. They said they continue to recommend 21 Gy in three treatments after high-risk procedures.

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: Randomised controlled trial (short communication). Procedure sites were randomised after stratification by procedure type and analysed on an intent-to-treat basis.
• Who was studied: 58 procedure sites from 43 patients with histologically confirmed malignant pleural mesothelioma, aged over 18, at Sir Charles Gairdner Hospital, Perth, Australia, registered between December 1997 and July 2003. Mean age was 70.0 years in both arms, and 55 of 58 sites were in men.
• Exposure: No asbestos exposure was studied. The intervention was a single 10 Gy chest wall radiotherapy dose with 9-MeV electrons, given within 15 days of thoracic procedures (thoracic drain or thoracoscopy, Abrams needle, or fine needle aspiration). It was compared with no preventive treatment. One patient assigned to the control arm received the radiotherapy at that patient's request.
• Main results:
  • Tract metastases developed at 3 (10%) of the 30 control-arm sites and at 2 (7%) of the 28 radiotherapy-arm sites. The difference was not statistically significant (P = 0.53).
  • Freedom from tract metastasis over time did not differ significantly between the two arms on log rank testing (P = 0.82).
  • Across all sites, crude tract metastasis rates were 22% after Abrams needles, 9% after thoracic drains and 4% after fine needle aspiration. These rates were not statistically significantly different (P = 0.23).
  • Early and late radiotherapy side effects were mild, with no grade 2, 3 or 4 reactions on the RTOG/EORTC criteria.
  • Overall median survival from randomisation was 8.7 months, and 1-year survival was 35%.
• The authors' conclusion: The authors concluded that a single 10 Gy dose with 9-MeV electrons does not appear effective in preventing procedure tract metastasis. As a possible explanation, they pointed to the lower dose. Using the linear-quadratic model, they estimated it was equivalent to about 40% of reported three-fraction schedules. They considered inadequate penetration of 9-MeV electrons a less likely explanation. They stated they continue to recommend 21 Gy in three fractions after high-risk procedures.
• Limitations the authors state:
  • The authors noted that tract metastases in the control arm were low. The trial had been designed assuming an expected rate of 20% without treatment.

Topics

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

Medical terms in this study, explained in our Lexicon: Tract Metastasis, Mesothelioma, Pleural Mesothelioma.

Related studies

• Prophylactic radiotherapy for the prevention of procedure-tract metastases after surgical and large-bore pleural procedures in malignant pleural mesothelioma (SMART): a multicentre, open-label, phase 3, randomised controlled trial — A.O. Clive, H. Taylor, et al. (2016)
• Prophylactic radiotherapy to prevent procedure-tract metastases — G. Zalcman, S. Brosseau, et al. (2016)
• Prophylactic radiotherapy to prevent procedure-tract metastases — D. Landau, E. Lim (2016)
• Protocol for the surgical and large bore procedures in malignant pleural mesothelioma and radiotherapy trial (SMART Trial): an RCT evaluating whether prophylactic radiotherapy reduces the incidence of procedure tract metastases — A.O. Clive, P. Wilson, et al. (2015)
• Catheter Tract Metastasis in Mesothelioma Patients with Indwelling Pleural Catheters: A Retrospective Cohort Study — M.A. Mitchell, P. Li, et al. (2019)
• Protocol for PIT: a phase III trial of prophylactic irradiation of tracts in patients with malignant pleural mesothelioma following invasive chest wall intervention — N. Bayman, D. Ardron, et al. (2016)

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