Prophylactic radiotherapy to prevent procedure-tract metastases

Our plain-English summary of Prophylactic radiotherapy to prevent procedure-tract metastases, by G. Zalcman, S. Brosseau, A. Scherpereel (The Lancet. Oncology, 2016).

The study

• Authors: G. Zalcman, S. Brosseau, A. Scherpereel
• Journal: The Lancet. Oncology
• Published: 2016;17(10):e417
• Type of article: Letter, Comment
• Cited by: 8 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Summary of the article

In this letter, the authors responded to the SMART randomised trial by Clive and colleagues. That trial compared early with deferred radiotherapy to prevent procedure-tract metastases (PTM) in malignant pleural mesothelioma, and the authors argued that its main conclusion could be challenged. The trial had assumed a PTM incidence of 2% with immediate radiotherapy, but 8·8% was observed, in line with earlier reports of 7% to 24%. The authors calculated that detecting a fall from 10% to 5% would have required 239 patients per group, so the trial was underpowered. PTM occurred in 16 of 101 patients given deferred radiotherapy and nine of 102 given early radiotherapy (p=0·14). The authors noted major protocol violations in the early group: radiation fields under 7 cm in eight patients, and a first fraction after the 42-day limit in three. They noted that the prespecified per-protocol analysis showed PTM in 16 (16%) of 99 versus five (6%) of 84 patients (p=0·037). They also cited a significant effect in patients who received no chemotherapy (OR 0·16 [0·02–0·93]; p=0·021). They argued that the quality-of-life and pain analyses were prone to be negative. They concluded that early prophylactic radiotherapy to intervention sites has a place in mesothelioma, provided technical requirements (high energy electrons, cutaneous bolus, 7 cm margins, daily 7 Gy fractions for 3 days) are respected.

PubMed has no abstract for this study, and the article doesn't print one. We wrote this summary from the full article with the help of AI. It is not the authors' wording.

In plain English

This is a letter to the editor, not a new study. The authors were responding to the SMART trial by Clive and colleagues. That randomised trial included patients with malignant pleural mesothelioma. It compared early radiotherapy to the sites of chest procedures with deferred radiotherapy, to prevent tumour growing along the procedure tract (procedure-tract metastases). The letter's authors argued that the trial's main conclusion could be challenged. They wrote that the trial assumed only 2% of patients would develop these metastases after immediate radiotherapy, but 8.8% did. By their calculation, detecting a fall from 10% to 5% would have needed 239 patients per group, so the trial was underpowered. As they reported the trial's figures, 16 of 101 patients in the deferred group and nine of 102 in the early group developed these metastases (p value 0.14). In the trial's per-protocol analysis, the figures were 16 of 99 versus five of 84 (p=0.037). They also pointed to protocol violations and to results in patients who received no chemotherapy. The authors concluded that early prophylactic radiotherapy has a place in mesothelioma, provided specified technical standards are respected.

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 (SMART); not original research
• Who was studied: No population of the letter's own; it discusses patients with malignant pleural mesothelioma in the SMART trial by Clive and colleagues (101 in the deferred radiotherapy group, 102 in the early radiotherapy group)
• Exposure: Not an asbestos exposure study. The intervention discussed was early prophylactic radiotherapy to procedure sites, compared with deferred radiotherapy.
• Main results:
  • The letter's authors reported that procedure-tract metastases occurred in 8·8% of the SMART trial's experimental (immediate radiotherapy) group, against an assumed 2%.
  • By the letter's authors' calculation, detecting a decrease from 10% to 5% would have required 239 patients per group. They concluded the trial was underpowered.
  • As reported in the letter, the SMART trial found procedure-tract metastases in 16 of 101 patients in the deferred radiotherapy group and nine of 102 patients in the early radiotherapy group, with a p value of 0·14.
  • The letter's authors noted major protocol violations in the experimental group: radiation fields too small (less than 7 cm) in eight patients, and three patients who received their first fraction beyond the 42-day limit.
  • In the SMART trial's prespecified per-protocol analysis, as cited in the letter, procedure-tract metastases occurred in 16 (16%) of 99 patients in the deferred group and five (6%) of 84 patients in the immediate radiotherapy group (p=0·037).
  • In patients who received no chemotherapy, the letter reported an odds ratio of 0·16 (0·02 to 0·93; p=0·021) for immediate radiotherapy.
  • The SMART authors reported no significant difference in quality of life or chest pain scores. The letter's authors argued these analyses were prone to be negative.
• The authors' conclusion: The authors concluded that there is a place for early, prophylactic radiotherapy to intervention sites in mesothelioma, provided that the technical radiotherapy standards they list are respected.

Topics

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

Medical terms in this study, explained in our Lexicon: Pleural Mesothelioma, Chemotherapy, Prophylactic Tract Irradiation, Mesothelioma.

Related studies

• Prophylactic radiotherapy to prevent procedure-tract metastases — D. Landau, E. Lim (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)
• 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)
• 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)
• To seed or not to seed: the open question of mesothelioma intervention tract metastases — L. Bertolaccini, A. Viti, et al. (2014)

Browse more research in The Lancet. Oncology, or return to medical research.