Prophylactic irradiation of tracts in patients with malignant pleural mesothelioma: A systematic review and meta-analysis of randomized trials

Our plain-English summary of Prophylactic irradiation of tracts in patients with malignant pleural mesothelioma: A systematic review and meta-analysis of randomized trials, by C.C. Lee, Y.Y. Soon, B. Vellayappan, et al (Critical Reviews in Oncology/hematology, 2021).

The study

• Authors: C.C. Lee, Y.Y. Soon, B. Vellayappan, C.N. Leong, W.Y. Koh, J.C.S. Tey
• Journal: Critical Reviews in Oncology/hematology
• Published: 2021;160:103278
• Type of article: Meta-analysis, Systematic review
• Cited by: 6 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Introduction: The role of prophylactic irradiation of tracts (PIT) to prevent tumor seeding at the site of a diagnostic or therapeutic intervention in patients with malignant pleural mesothelioma (MPM) is controversial. This study aimed to determine the efficacy of PITs in preventing procedure tract metastases (PTM) after a chest wall procedure in MPM.

Materials And Methods: We searched various databases from inception date to April 2020 for randomized controlled trials (RCTs) comparing PIT with no PIT in patients who had a chest wall procedure for MPM. We assessed the risk of bias of individual RCT using the RoB2 tool. The primary outcome was the occurrence of PTM. Meta-analysis was performed using random-effects model. We employed the GRADE approach to assess the certainty of the evidence.

Results: We identified five RCTs including 737 patients. Two RCTs had a low risk of bias. PIT was associated with a significant reduction in the odds of PTM (odd ratio, 0.55; 95 % confidence interval, 0.32 to 0.95; P-value = 0.03; I2 = 13 %; GRADE: moderate certainty). One RCT reported no difference in overall survival outcome with the use of PIT. None of the RCTs performed subgroup analyses. Sensitivity analyses showed similar results when limited to RCTs with low risk of bias.

Conclusion: PIT significantly reduces the occurrence of PTM in patients with MPM who had a diagnostic or therapeutic chest wall procedure.

Copyright © 2021 Elsevier B.V. All rights reserved.

In plain English

This systematic review pooled five randomized trials (1995 to 2019) of 737 patients with malignant pleural mesothelioma who had a chest wall procedure. The trials compared prophylactic irradiation of the procedure tract with no prophylactic tract irradiation. Across all five trials, irradiation was associated with lower odds of cancer growing along the procedure tract (odds ratio 0.55; 95% confidence interval 0.32 to 0.95). Results were similar in the two trials judged at low risk of bias (odds ratio 0.54; 95% confidence interval 0.32 to 0.90). With two other statistical methods, however, the intervals included no effect. Limited to those two trials at the 12-month point, the reduction was not statistically significant (odds ratio 0.66; 95% confidence interval 0.38 to 1.15). In three trials reporting skin side effects, irradiation was associated with higher odds of grade 2 or worse skin toxicity (odds ratio 11.22; 95% confidence interval 2.42 to 51.96). The one trial reporting survival found no statistically significant difference. The authors concluded this irradiation can reduce tract metastases but is unlikely to alter survival or disease course.

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: Systematic review and meta-analysis of randomized controlled trials
• Who was studied: 737 patients with malignant pleural mesothelioma who had a chest wall procedure (such as thoracoscopy or chest drain insertion), from five randomized trials published between 1995 and 2019. The databases were searched up to April 2020.
• Exposure: The study compared prophylactic irradiation of procedure tracts with no prophylactic tract irradiation. Four trials used 21 Gy in 3 fractions over 3 days and one used 10 Gy in a single fraction. Asbestos exposure was not studied.
• Main results:
  • Across all five trials, irradiation was associated with reduced odds of procedure tract metastases: odds ratio 0.55, 95% confidence interval 0.32 to 0.95, P = 0.03. The authors rated the certainty of this evidence as moderate.
  • In sensitivity analyses using two alternative statistical models, the point estimates were similar: odds ratio 0.52 (95% CI 0.18 to 1.48) and odds ratio 0.41 (95% credible interval 0.05 to 1.33). However, both intervals included odds ratios above 1.
  • Limited to the two trials judged at low risk of bias, the odds ratio for procedure tract metastases was 0.54, 95% confidence interval 0.32 to 0.90, P = 0.02.
  • For the two low-risk-of-bias trials at the 12-month time point, the reduction was not statistically significant: odds ratio 0.66, 95% confidence interval 0.38 to 1.15, P = 0.14.
  • In the three trials that reported skin toxicity, irradiation was associated with increased odds of grade 2 or greater skin toxicity: odds ratio 11.22, 95% confidence interval 2.42 to 51.96.
  • The one trial that reported overall survival found no statistically significant difference between the irradiation and no-irradiation arms: hazard ratio 1.00, 95% confidence interval 0.68 to 1.46. The 12-month survival rate was 49% in both arms.
  • For the largest trial (Bayman et al.), the analysis used the total number of tract metastases in each arm at 2 years: 17 in the irradiation arm and 29 in the control arm. The authors note this was not a primary or secondary endpoint of that trial.
• The authors' conclusion: The authors concluded that prophylactic irradiation of tracts can reduce procedure tract metastases in patients with malignant pleural mesothelioma who had chest wall procedures, with toxicity limited to the skin. They added that survival and disease course are unlikely to be altered.
• Limitations the authors state:
  • Without individual patient data, the authors could not identify which subgroups of patients benefit most.
  • The included trials were not designed to determine whether treating tract metastases later, if they appear (salvage treatment), is more appropriate than preventive irradiation.

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, Systematic Review, Meta-Analysis, confidence interval, P-Value, Overall Survival.

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