Prophylactic radiotherapy to prevent procedure-tract metastases

Our plain-English summary of Prophylactic radiotherapy to prevent procedure-tract metastases, by D. Landau, E. Lim (The Lancet. Oncology, 2016).

The study

• Authors: D. Landau, E. Lim
• Journal: The Lancet. Oncology
• Published: 2016;17(10):e418
• Type of article: Letter, Comment
• Cited by: 2 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

In plain English

This is a short letter to the editor, not a new study. Its two authors commented on the SMART trial by Clive and colleagues. That trial tested prophylactic radiotherapy to prevent procedure-tract metastases (cancer spreading along the track of a surgical or large-bore pleural procedure) in malignant pleural mesothelioma. The letter noted that the trial's authors concluded there was no difference between immediate and deferred radiotherapy, despite an odds ratio of 0.51 (95% CI 0.19 to 1.32) in favour of radiotherapy in the intention-to-treat analysis. The letter's authors argued that the trial's planning assumed a fall from 15% to 2%, which they calculated as an odds ratio of 0.12 and called overly optimistic. From the trial's figures of 9 (9%) metastases with immediate and 16 (16%) with deferred radiotherapy, they calculated a relative risk of 0.56 and a number needed to treat of 14. They would have preferred a time-to-event analysis. The authors wrote that whether this reduction is meaningful is for each patient to decide. They called for pooling the results with the PIT study.

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: Letter to the editor (correspondence) commenting on a published randomised trial; no new data collected
• Who was studied: No population of its own. The letter discusses the SMART trial (Clive and colleagues, Lancet Oncology 2016) in patients with malignant pleural mesothelioma after surgical and large-bore pleural procedures
• Exposure: Not asbestos exposure. The intervention discussed was prophylactic radiotherapy, given immediately or deferred, to prevent procedure-tract metastases
• Main results:
  • As reported by the SMART trial: odds ratio 0.51 (95% CI 0.19 to 1.32) in the intention-to-treat analysis, in favour of immediate radiotherapy. The trial's authors concluded there was no difference between groups
  • The trial's sample size assumed procedure-tract metastases would fall from 15% (deferred) to 2% (immediate). The letter's authors calculated this as an odds ratio of 0.12 and said many would consider it overly optimistic
  • The letter's authors disagreed with a published Comment (Ceresoli and colleagues) that the trial was adequately powered
  • The trial used the odds ratio as its primary outcome rather than a time-to-event analysis. The letter's authors would have preferred a time-to-event analysis expressed as a hazard ratio for disease-free survival
  • Trial incidence of procedure-tract metastases: 9 (9%) in the immediate radiotherapy group vs 16 (16%) in the deferred group
  • From these figures the letter's authors calculated a relative risk of 0.56 for patients assigned to early prophylactic radiotherapy, corresponding to a number needed to treat of 14
• The authors' conclusion: The authors wrote that whether the reduction is meaningful would be up to the individual patient to decide. They looked forward to the PIT study (NCT01604005) and to pooling its results with SMART before a potentially useful intervention is inappropriately abandoned

Topics

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

Related studies

• Prophylactic radiotherapy to prevent procedure-tract metastases — G. Zalcman, S. Brosseau, et al. (2016)
• 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 for procedure tract metastases in mesothelioma: a review — D.T. Arnold, A.O. Clive (2017)
• Pleurectomy/decortication, hyperthermic pleural lavage with povidone-iodine, prophylactic radiotherapy, and systemic chemotherapy in patients with malignant pleural mesothelioma: a 10-year experience — L. Lang-Lazdunski, A. Bille, et al. (2015)
• Prophylactic irradiation of tracts in patients with malignant pleural mesothelioma: A systematic review and meta-analysis of randomized trials — C.C. Lee, Y.Y. Soon, et al. (2021)
• To seed or not to seed: the open question of mesothelioma intervention tract metastases — L. Bertolaccini, A. Viti, et al. (2014)

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