Extrathoracic Metastases in Pleural Mesothelioma

Our plain-English summary of Extrathoracic Metastases in Pleural Mesothelioma, by I. Dagogo-Jack, B.Y. Yeap, M. Mino-Kenudson, et al (JTO Clinical and Research Reports, 2023).

The study

• Authors: I. Dagogo-Jack, B.Y. Yeap, M. Mino-Kenudson, S.R. Digumarthy
• Journal: JTO Clinical and Research Reports
• Published: 2023;4(9):100557
• Cited by: 14 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Introduction: Guidelines recommend obtaining a computed tomography scan of the chest for the staging of pleural mesothelioma and for assessing response to treatment. Consensus is lacking regarding the necessity of serial imaging of distant extrathoracic sites. In this study, we determined the prevalence of extrathoracic metastases in patients with pleural mesothelioma.

Methods: We conducted a retrospective review of patients with pleural mesothelioma treated at Massachusetts General Hospital between 1999 and 2022 who were referred for extrathoracic imaging during their disease course. Imaging reports were reviewed to determine sites of metastasis and calculate the time to development of extrathoracic metastasis. Overall survival and prevalence of extrathoracic metastasis were compared for patients with epithelioid versus nonepithelioid mesothelioma.

Results: The study included 148 patients, 69 (47%) of whom had undergone cytoreductive surgery. Histologic types included epithelioid (n = 82, 55%), biphasic (n = 49, 33%), and sarcomatoid (n = 10, 7%) mesothelioma. The median overall survival for the cohort was 24.0 months, specifically 34.7 months and 16.7 months for patients with epithelioid and nonepithelioid tumors, respectively (p < 0.001). There were 65 (44%) patients who developed extrathoracic metastases, with a median time to extrathoracic metastasis of 11.5 months. The most common sites of involvement were extrathoracic nodes (22%), peritoneum (20%), bone (11%), and liver (11%). Of the 76 patients referred for brain imaging, seven (9%) had brain metastases. The frequency of extrathoracic metastasis was identical for epithelioid and nonepithelioid mesothelioma (44%). Overall survival was shorter for patients who developed extrathoracic metastases (hazard ratio 5.9, p < 0.001).

Conclusions: Patients with pleural mesothelioma often develop extrathoracic metastases, providing a rationale for routinely obtaining imaging that encompasses sites outside of the thoracic cavity.

© 2023 The Authors.

In plain English

This was a retrospective, single-institution review of patients with pleural mesothelioma treated at Massachusetts General Hospital between 1999 and 2022. Of 197 consecutive patients, the 148 who had abdominal imaging during follow-up were studied. The article does not report asbestos or other exposures. The authors reviewed CT, PET and MRI reports to find cancer spread outside the chest (extrathoracic metastases). Of the 148 patients, 65 (44%) developed extrathoracic metastases. In these 65 patients the median time from diagnosis was 11.5 months (95% CI 7.3 to 16.9). Among all 148 patients, the most common sites were abdominal or retroperitoneal lymph nodes (22%), peritoneum (20%), bone (11%) and liver (11%). Of the 76 patients who had brain imaging, seven had brain metastases. Spread outside the chest was equally common in epithelioid (36 of 82) and nonepithelioid (26 of 59) mesothelioma, 44% in each group. Median overall survival was 24.0 months (95% CI 18.6 to 30.5). Patients who developed extrathoracic metastases had shorter survival (hazard ratio 5.9). The authors concluded that pleural mesothelioma often spreads outside the chest. Their stated limitations included irregularly timed imaging, often suboptimal brain imaging, and no biopsy confirmation for most metastases.

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, single-institution review of medical records and imaging reports
• Who was studied: 148 patients with pleural mesothelioma treated at Massachusetts General Hospital (Boston) between 1999 and 2022 who had abdominal imaging during follow-up. They were selected from 197 consecutive patients after excluding 49 without such imaging. 74% were male and the median age was 69 years. Histology: 82 epithelioid, 49 biphasic, 10 sarcomatoid, 7 not subtyped. 69 had cytoreductive surgery.
• Exposure: Not addressed. The article does not report asbestos or other exposures; it studied where and when the disease spread outside the chest.
• Main results:
  • 65 of the 148 patients (44%) developed extrathoracic metastases.
  • Among the 65 patients with extrathoracic metastases, the median time from diagnosis to extrathoracic metastasis was 11.5 months (95% CI: 7.3–16.9).
  • Most common extrathoracic sites, as counts and percentages of all 148 patients: abdominal or retroperitoneal nodes 32 (22%); peritoneum, omentum or ascites 30 (20%); bone 17 (11%); liver 16 (11%).
  • Of the 65 patients with extrathoracic disease, 37 (57%) had involvement of more than one organ.
  • Brain imaging was done for 76 of the 148 patients (51%): 49 had brain MRI and 27 had only a head CT.
  • Brain metastases were found in 7 patients, which is 9% of the 76 who had brain imaging. All 7 also had extrathoracic metastases.
  • Extrathoracic metastases were equally common in nonepithelioid (26 of 59, 44%) and epithelioid (36 of 82, 44%) mesothelioma (p = 1.000).
  • Median overall survival for the whole cohort was 24.0 months (95% CI 18.6–30.5).
  • Median overall survival was 34.7 months for epithelioid tumors versus 16.7 months for biphasic and sarcomatoid tumors combined (p less than 0.001).
  • Overall survival was shorter for patients who developed extrathoracic metastases (hazard ratio 5.9, p less than 0.001).
• The authors' conclusion: The authors concluded that pleural mesothelioma often spreads to organs outside the chest. They stated that future imaging guidelines should consider these findings.
• Limitations the authors state:
  • Findings come from a single institution and a retrospective chart review.
  • Imaging outside the chest was not done at fixed intervals. Some scans may have been ordered because of symptoms or high-risk features.
  • Brain imaging was suboptimal for many patients (head CT without contrast).
  • Survival was better than in historical cohorts, and many patients had surgery and radiation. The findings may therefore not apply to all patients with pleural mesothelioma.
  • Most metastases were not confirmed by biopsy, so some may have come from other cancers.

Topics

Medical terms in this study, explained in our Lexicon: Pleural Mesothelioma, Staging, Metastasis, Overall Survival, Epithelioid, Mesothelioma, Cytoreductive Surgery, Biphasic Mesothelioma.

Related studies

• Extrathoracic lymph node metastases in malignant pleural mesothelioma — M. Huncharek, K. Smith (1988)
• Fibrosing pleuritis with extrathoracic extension — B.I. Hoffbrand, M.R. Hetzel, et al. (1985)
• Metastases to the breast: differential diagnosis from primary breast carcinoma — B. Vergier, M. Trojani, et al. (1991)
• Role of hyperthermic intraoperative peritoneal chemotherapy in the management of peritoneal metastases — D. Elias, D. Goéré, et al. (2014)
• 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)
• Cytoreductive surgery and intraoperative hyperthermic intrathoracic chemotherapy in patients with malignant pleural mesothelioma or pleural metastases of thymoma — E. de Bree, S. van Ruth, et al. (2002)

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