Prophylactic irradiation of intervention sites in malignant pleural mesothelioma

Our plain-English summary of Prophylactic irradiation of intervention sites in malignant pleural mesothelioma, by M.A. Froment, E. Fréchette, A. Dagnault (Radiotherapy and Oncology, 2011).

The study

• Authors: M.A. Froment, E. Fréchette, A. Dagnault
• Journal: Radiotherapy and Oncology
• Published: 2011;101(2):307-10
• Cited by: 12 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Background And Purpose: To assess the effectiveness of prophylactic irradiation of intervention track (PIT) to prevent tumor seeding in patients with malignant pleural mesothelioma.

Materials And Methods: A retrospective review was conducted of 171 patients with a histological diagnosis of pleural mesothelioma with some undergoing prophylactic irradiation of intervention sites.

Results: Forty-eight patients (28%) received PIT. A majority of patients were followed until death. Thoracoscopy (88%) was the procedure most often performed. Thirty-three percent of patients received chemotherapy. The median dose of PIT was 21 Gy in 3 fractions with electrons or 6 MV photons. The local progression free survival (LPFS) at the intervention site was significantly higher in the PIT group and was not influenced by chemotherapy. At 6 months, LPFS for the intervention sites was 91% with PIT and 74% without PIT (p=0.002). During the follow-up, 6 patients (13%) in the PIT group had tumor invasion of the subcutaneous tissue compared to 40 patients (33%) in the group without PIT (p=0.008).

Conclusions: This study suggests that PIT in mesothelioma reduces the incidence of procedure tract metastasis. Finally, chemotherapy does not seem to have an influence on the incidence of tract metastasis.

Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.

In plain English

This was a retrospective review of case files from two university medical centers in Québec, Canada, covering patients treated for malignant pleural mesothelioma between June 1985 and March 2009. Of 171 patients included, 48 received prophylactic radiotherapy to procedure sites, mostly thoracoscopy ports; 40% of them received 21 Gy in 3 fractions and 44% received 20 Gy in 4 or 5 fractions. The other 123 did not. About half of all patients had previous asbestos exposure. Tumor growth under the skin at a procedure site developed in 6 of 48 irradiated patients (13%) and 40 of 123 non-irradiated patients (33%) (p = 0.008). Freedom from this local progression at 6 months was 91% with radiotherapy and 74% without. That difference, and better survival with radiotherapy, were seen in the unadjusted analysis but were not statistically significant after adjustment for other factors. Two patients had grade I acute side effects. The authors concluded that this radiotherapy may reduce procedure tract metastasis and should be considered. They also concluded that chemotherapy did not prevent these metastases. They acknowledged the limitations of a retrospective 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: retrospective review of case files (cohort of patients with and without prophylactic irradiation of intervention sites)
• Who was studied: 171 patients with histologically confirmed malignant pleural mesothelioma, treated at two university medical centers in Québec, Canada, June 1985 to March 2009. 48 received prophylactic irradiation (PIT) and 123 did not. Patients with under 1 month of follow-up, no confirmed diagnosis, or surgical resection were excluded. Median follow-up was 14 months in the PIT group and 8.5 months in the non-PIT group.
• Exposure: Prophylactic radiotherapy to intervention sites, mostly thoracoscopy port sites (88%). Median dose was 21 Gy in 3 fractions (range 20 to 52.25 Gy), given with electrons or 6 MV photons. 40% received 21 Gy in 3 fractions, 44% received 20 Gy in 4 or 5 fractions, and 6% received 30 Gy in 3 fractions. Asbestos exposure was recorded only as a patient characteristic.
• Main results:
  • Procedure tract metastases (tumor under the skin) developed in 6 of 48 PIT patients (13%) and 40 of 123 non-PIT patients (33%), p = 0.008.
  • All 6 tract metastases in the PIT group occurred within the radiotherapy field.
  • Local progression-free survival at the intervention site at 6 months was 91% with PIT and 74% without PIT. The difference was significant in univariate analysis (p = 0.002).
  • At 12 months, local progression-free survival was 86% with PIT and 63% without PIT.
  • In the multivariate analysis, the local progression-free survival difference was not statistically significant.
  • At 1 year, cancer-specific survival was 67% with PIT and 46% without PIT (p = 0.04), in univariate analysis.
  • At 1 year, overall survival was 67% with PIT and 40% without PIT (p = 0.04), in univariate analysis.
  • The survival differences were not maintained in multivariate analysis. Disease extension was the only statistically significant factor for survival.
  • More PIT patients than non-PIT patients received chemotherapy, as printed 58% vs. 21% (p less than 0.001).
  • In multivariate analysis, chemotherapy did not influence local progression-free survival.
  • The delay between procedure and irradiation (27 days or less vs. more than 27 days) had no statistically significant impact on tract metastasis (p = 0.8).
  • Two patients had grade I acute radiotherapy toxicities: one radiodermatitis and one nausea.
  • No late toxicity was found in the case files.
  • Work-related asbestos exposure was recorded in 21 of 48 PIT patients (44%) and 51 of 123 non-PIT patients (41%).
• The authors' conclusion: The authors concluded that prophylactic radiotherapy to intervention sites in mesothelioma may reduce the incidence of procedure tract metastasis and should be considered. They also concluded that it was well tolerated and that, in this study, chemotherapy did not prevent biopsy tract metastases.
• Limitations the authors state:
  • The authors acknowledged the limitations of a retrospective study.
  • The authors suggested that the lack of a chemotherapy effect on survival may be due to a lack of statistical power.
  • Patients received different chemotherapy regimens, with different drugs and doses.
  • The groups differed: more PIT patients had disease confined to the thorax (p = 0.07).

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, Thoracoscopy, Chemotherapy, Mesothelioma, Tract Metastasis.

Related studies

• Prevention of malignant seeding at drain sites by hypofractionated radiotherapy in patients with pleural mesothelioma — P. Kara, I. Ugur, et al. (2010)
• Should all patients who have mesothelioma diagnosed by video-assisted thoracoscopic surgery have their intervention sites irradiated? — M. Nagendran, A. Pallis, et al. (2011)
• Tumor extension along chest wall tract after diagnostic intervention in malignant pleural mesothelioma — F. Chen, A. Yoshizawa, et al. (2011)
• 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)
• Prophylactic radiotherapy for procedure tract metastases in mesothelioma: a review — D.T. Arnold, A.O. Clive (2017)
• FDG PET/CT is useful for detecting infiltration to the port site in patients with malignant pleural mesothelioma — K. Kawaguchi, T. Taniguchi, et al. (2014)

Browse more research in Radiotherapy and Oncology, or return to medical research.