The Role of Adjuvant Radiotherapy in the Treatment of Pleural Mesothelioma

Our plain-English summary of The Role of Adjuvant Radiotherapy in the Treatment of Pleural Mesothelioma, by G.D. Lewis, S.M. Dalwadi, A. Farach, et al (Annals of Surgical Oncology, 2019).

The study

• Authors: G.D. Lewis, S.M. Dalwadi, A. Farach, E. Brian Butler, B.S. Teh
• Journal: Annals of Surgical Oncology
• Published: 2019;26(6):1879-1885
• Cited by: 12 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Background: Pleural mesothelioma is a rare but aggressive form of cancer. Local recurrence represents the majority of treatment failures and overall survival (OS) outcomes remain dismal. Adding locoregional treatment with radiotherapy after surgical resection has been considered but its role remains uncertain.

Objective: The purpose of this study was to evaluate the outcomes of adjuvant radiation therapy (RT) for patients with malignant pleural mesothelioma.

Methods: The National Cancer Data Base (NCDB) was queried (2004-2013) for patients with malignant mesothelioma. Patients were divided into three groups: observation, surgery alone, and surgery followed by adjuvant RT. Statistics included Fisher's exact or Chi square tests to analyze categorical proportions between groups, Kaplan-Meier analysis to evaluate OS, and Cox proportional hazards modeling to determine variables associated with OS. Propensity matching was performed to make comparisons between homogenous groups.

Results: Overall, the surgery plus radiotherapy group had a higher median survival (21.4 months) compared with surgery alone (16.59 months) [p < 0.001]. RT was more likely to be delivered after extrapleural pneumonectomy than with lung-sparing surgical approaches. On multivariable analysis, receipt of surgery plus radiotherapy, chemotherapy administration, and higher socioeconomic status were associated with improved OS (p < 0.0001). After propensity matching, receipt of surgery plus radiotherapy and chemotherapy administration were still associated with improved OS (p < 0.05).

Conclusions: In the treatment of malignant pleural mesothelioma, adjuvant radiotherapy after surgical intervention was associated with improved OS. This study is the largest study of adjuvant radiotherapy to date, and our findings highlight the need for additional prospective data.

In plain English

This retrospective study used the US National Cancer Data Base (2004 to 2013) to examine survival after adjuvant radiotherapy (radiation following surgery) in malignant pleural mesothelioma. It did not study asbestos exposure. Of 24,914 patients, 17,262 had no local treatment, 5918 had surgery alone, and 762 had surgery followed by at least 40 Gy of radiation; these groups do not add up to the total, and the article does not explain why. Median survival was 21.42 months (95% CI 19.71 to 22.51) with surgery plus radiation, 16.59 months (15.84 to 17.31) with surgery alone, and 7.59 months (7.39 to 7.75) with no local treatment. Patients given radiation more often had private insurance, higher income, epithelioid histology and fewer other illnesses, and more often received chemotherapy. After adjustment, and again after matching 454 patients per surgery group, surgery plus radiation and chemotherapy were associated with better survival. The authors concluded that adjuvant radiotherapy after surgery was associated with improved overall survival. They noted possible selection bias and that the database lacks data on tolerance of therapy and reasons for treatment decisions.

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 analysis of a national hospital-based cancer database (National Cancer Data Base), using survival analysis, multivariable Cox modeling and propensity score matching
• Who was studied: 24,914 patients with histologically confirmed malignant mesothelioma in the US National Cancer Data Base, 2004 to 2013, with recorded vital status and staging. Patients with metastatic disease were included.
• Exposure: The study examined treatment, not asbestos exposure. It compared three groups: no local therapy (observation), surgery alone, and surgery followed by adjuvant radiotherapy of at least 40 Gy. Lower doses were excluded as palliative. No fiber types or asbestos exposures were studied.
• Main results:
  • Group sizes: 17,262 (69.3%) received no local intervention, 5918 (23.8%) had surgery alone, and 762 (3.1%) had surgery plus radiation. Summed, these three counts come to 23,942, fewer than the 24,914 included patients. The article does not explain the difference.
  • In the whole cohort, median survival was 21.4 months in the surgery plus radiotherapy group, 7.6 months in the observation group and 16.59 months in the surgery alone group. Table 3 gives 21.42 months (95% CI 19.71 to 22.51) for surgery and radiation, 16.59 (15.84 to 17.31) for surgery alone and 7.59 (7.39 to 7.75) for observation, p less than 0.001.
  • 1-year survival was 76.5% with surgery and radiation, 60.2% with surgery alone and 35.9% with observation. 2-year survival was 42.7%, 38.8% and 16.6% respectively (Table 3).
  • Patients who received adjuvant radiotherapy more often had locoregional disease, private insurance, higher income, epithelioid histology and a lower comorbidity score.
  • Patients who received adjuvant radiotherapy were more likely to receive chemotherapy: 72.7% in the surgery and radiation group versus 58.7% with surgery only and 46.4% with observation (Table 2).
  • Among surgical patients, radiation was more common after extrapleural pneumonectomy (EPP) than after lung-sparing surgery such as pleurectomy and decortication.
  • On multivariable analysis of the whole cohort, the following were associated with improved overall survival: surgery plus radiotherapy (hazard ratio 0.63 versus observation; surgery only 0.70), chemotherapy (hazard ratio 0.65) and higher socioeconomic status. p less than 0.0001 for each (Table 4).
  • On the same analysis, the following were associated with worse overall survival: male sex, advancing age, higher Charlson-Deyo comorbidity score, fibroid (sarcomatoid) and biphasic histologies, and lower socioeconomic status.
  • After propensity matching (454 surgery alone, 454 surgery plus radiotherapy), radiotherapy remained associated with improved overall survival: hazard ratio 0.88 versus surgery only, p = 0.0313. So did chemotherapy: hazard ratio 0.84, p = 0.0369 (Table 5).
• The authors' conclusion: The authors concluded that, in malignant pleural mesothelioma, adjuvant radiotherapy after surgery was associated with improved overall survival.
• Limitations the authors state:
  • Because the study was retrospective, selection bias was possible. Propensity matching was used to reduce it.
  • The database does not record tolerance of therapy, cancer-specific survival or local/regional control.
  • The database lacks the reasons behind treatment decisions and data on targeted or salvage treatments.
  • Only Commission on Cancer-accredited facilities report to the database.

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, Overall Survival, Surgical Resection, Mesothelioma, Median Overall Survival, Extrapleural Pneumonectomy (EPP), Chemotherapy.

Related studies

• Adjuvant radiotherapy after extrapleural pneumonectomy for mesothelioma. Prospective analysis of a multi-institutional series — S. Tonoli, P. Vitali, et al. (2011)
• Malignant Peritoneal Mesothelioma: Patterns of Care and Survival in the Netherlands: A Population-Based Study — N.L. de Boer, J.P. van Kooten, et al. (2019)
• Cancer survival and prevalence in Australia: period estimates from 1982 to 2010 — Australian Institute of Health and Welfare (2013)
• Analysis of the effect of radiotherapy on malignant pleural mesothelioma when given on adjuvant or palliative basis — H.A. El Hossieny, F. Aboulkasem, et al. (2010)
• Pattern of failure after adjuvant radiotherapy following extrapleural pneumonectomy of pleural mesothelioma in the SAKK 17/04 trial — O. Riesterer, I.F. Ciernik, et al. (2019)
• Geographic study of mortality due to mesothelioma in Peru and its evolution — J.S. Torres-Roman, V. Gomez-Rubio, et al. (2020)

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