Malignant Pleural Mesothelioma: Current Understanding of the Immune Microenvironment and Treatments of a Rare Disease

Malignant pleural mesothelioma is a rare disease with an annual incidence of around 3000 cases a year in the United States. Most cases are caused by asbestos exposure, with a latency period of up to 40 years. Pleural mesothelioma is an aggressive disease process with overall survival of roughly 6-12 months after the time of diagnosis. It is divided into three subtypes: epithelioid, mixed type, and sarcomatoid type, with the epithelioid subtype having the best overall survival. Often, the treatment is multimodality with surgery, chemotherapy, and radiation. The survival benefit is improved but remains marginal. New treatment options involving targeted immune therapies appear to offer some promise. The tumor microenvironment is the ecosystem within the tumor that interacts and influences the host immune system. Understanding this complex interaction and how the host immune system is involved in the progression of the disease process is important to define and guide potential treatment options for this devastating and rare disease.

Preserving the eponym: Klinkenbergh technique for bronchial stump suturing

The technique for bronchial stump suturing following lung resection which is currently applied in the Department of Thoracic Surgery at the University Hospitals Leuven, Belgium owes its name to the Dutch surgeon Dr. Klinkenbergh (1891-1985). A true pioneer of cardiothoracic surgery in Europe, Dr. Klinkenbergh dedicated himself to the surgical treatment of pulmonary tuberculosis. His work was praised by his peers for his precision and the reasoning behind every gesture. The Klinkenbergh technique consists in performing two running sutures which cross each other 'in the same manner as the laces of a shoe' to close the bronchus, limiting the occurrence of broncho-pleural fistulas. In our experience with more than 100 patients in the last 5 years (2016-2020) who underwent open pneumonectomy for benign or malignant disease, less than 2% developed post-operative broncho-pleural fistulas.

Use of Continuous Positive Airway Pressure (CPAP) to Limit Diaphragm Motion-A Novel Approach for Definitive Radiation Therapy for Inoperable Pleural Mesothelioma: A Pilot Study

Simple Summary

Radiotherapy is an important part of the multimodality approach to treating malignant pleural mesothelioma. In recent studies there is a new trend to treat patients with intact lungs instead of following surgery. This treatment creates significant concerns regarding lung toxicity. We describe two methods to reduce that toxicity. One is the use of constant pulmonary airway pressure (CPAP) to inflate the lungs during treatment. The second is utilizing a novel method of planning and delivering radiotherapy called volumetric modulated arc therapy (VMAT).

Abstract

Malignant pleural mesothelioma (MPM) is a deadly disease and radiotherapy (RT) plays an important role in its management. Recent developments in technique have made it is possible to deliver RT to MPM in the intact lung. However, it is imperative to reduce normal lung doses. We present a pilot study examining the use of CPAP and VMAT radiotherapy to reduce toxicity when treating MPM, involving three consecutive patients with MPM, not amenable to surgery, who were treated according to Helsinki committee approval. Patients were simulated using four-dimentional CT simulation with the assistance of CPAP lung inflation, then were treated using both IMRT and VMAT techniques. Radiation lung dose was optimized based on accepted lung dose constraints. Patients were followed for toxicity as well as local control and survival. Results: Three patients were treated with CPAP-based IMRT treatment. These patients tolerated the treatment and DVH constraints were able to be met. The comparison plans among the four VMAT arcs and the IMRT static field treatment were able to accomplish the treatment planning objectives without significant advantages with either technique. The treatment combined with CPAP reduced the normal lung dose in MPM patients with intact lungs. This technique is worthy of further investigation.

Three Decades of Malignant Pleural Mesothelioma: An Academic Center Experience

BACKGROUND

Malignant pleural mesothelioma (MPM) remains a challenging disease to manage. In the past few decades, extrapleural pneumonectomy (EPP), pemetrexed-based chemotherapy, and indwelling pleural catheters were introduced to MPM care with variable levels of efficacy and evidence.

PATIENTS AND METHODS

This was a retrospective review of patients diagnosed with MPM between January 1991 and March 2019. The primary outcome was overall survival (OS). Data were examined by decade to assess trends in MPM demographics, management, and OS. A subgroup analysis was then conducted to examine the impact of EPP, pemetrexed, and indwelling pleural catheters on OS.

RESULTS

The study included 337 patients; 309 patients had died at last follow-up (91.7%). Median age at diagnosis and the proportion of female patients increased from 65.8 years (interquartile range [IQR], 57.1-73.7) and 11.6% female from 1991 to 1999 to 75 years (IQR, 68.1-80.6) and 20.5% female from 2010 to 2019. Median OS was largely unchanged in the three study periods: 9.0 months (95% confidence interval [CI], 6.9-12.7) in the 1991-1999 cohort, 9.3 months (95% CI, 7.6-13.2) in the 2000-2009 cohort, and 10.1 months (95% CI, 7.9-13.6) in the 2010-2019 cohort. Controlling for a number of demographic and prognostic factors, EPP (hazard ratio [HR] = 0.50; 95% CI, 0.3-0.9; P = .02), pemetrexed-based chemotherapy (HR = 0.59; 95% CI, 0.40-0.87; P = .007), and indwelling pleural catheters (HR = 0.3; 95% CI, 0.13-0.71; P = .006) were each associated with improvements in OS.

CONCLUSION

Despite the small incremental improvements in survival shown by the three interventions we examined, prognosis remains guarded for MPM patients. Better modalities of management are needed.

Surgery for malignant pleural mesothelioma after radiotherapy (SMART): final results from a single-centre, phase 2 trial

BACKGROUND

A novel approach for managing malignant pleural mesothelioma, surgery for mesothelioma after radiotherapy (SMART), consisting of a short accelerated course of high-dose, hemithoracic, intensity modulated radiotherapy (IMRT) followed by extrapleural pneumonectomy was developed. The aim of this study was to evaluate the clinical feasibility of the SMART protocol.

METHODS

In this single-centre, phase 2 trial, patients aged 18 years or older with an Eastern Cooperative Oncology Group performance status of 0-2, with histologically proven, resectable, cT1-3N0M0 disease who had previously untreated malignant pleural mesothelioma were eligible for inclusion. Patients received 25 Gy in five daily fractions over 1 week to the entire ipsilateral hemithorax with a concomitant 5 Gy boost to high risk areas followed by extrapleural pneumonectomy within 1 week. Adjuvant chemotherapy was offered to patients with ypN+ disease on final pathology. The primary endpoint was feasibility, which was defined as the number of patients with 30-day perioperative treatment-related death (grade 5 events) or morbidity (grade 3 or 4 events). A key secondary endpoint was cumulative incidence of distant recurrence. The final analysis was done on an intention-to-treat basis (including all eligible patients). This trial is registered with ClinicalTrials.gov, NCT00797719.

FINDINGS

Between Nov 1, 2008, and Oct 31, 2019, 102 patients were enrolled onto the trial and 96 eligible patients were treated with SMART on protocol and included in the analysis. Extrapleural pneumonectomy was done at a median of 5 days (range 2-12) after completing IMRT. 47 (49%) patients had 30-day perioperative grade 3-4 events and one (1%) patient died within 30 days perioperatively (grade 5 event; pneumonia). After a median follow-up of 46·8 months (IQR 13·4-61·2), the 5-year cumulative incidence of distant recurrence was 62 (63·3% [95% CI 52·3-74·4]). The most common first sites of recurrence were the contralateral chest (33 [46%] of 72 patients) and the peritoneal cavity (32 [44%]).

INTERPRETATION

Results from this study suggest that extrapleural pneumonectomy after radiotherapy can be done with good early and long-term results. However, minimising grade 4 events on the protocol is technically demanding and might affect survival beyond the post-operative period.

FUNDING

Princess Margaret Hospital Foundation Mesothelioma Research Fund.

Extrapleural pneumonectomies for pleural mesothelioma

Introduction: Malignant pleural mesothelioma (MPM) is a fatal malignancy for which there is no definitive cure. The most effective multimodality treatment in prolonging survival is still matter of debate. Surgery remains one of the cornerstones in the multimodality therapy for MPM. Extra-pleural pneumonectomy and pleurectomy/decortication are the two main curative-intent procedures; however, the superiority of one technique over the other is still debated. This review aims to assess short- and long-term results of extrapleural pneumonectomy for MPM.Areas covered: This article focuses on the role of extrapleural pneumonectomy in MPM. A systematic review was performed by using electronic databases to identify studies that included patients treated by this procedure for MPM. Endpoints included overall survival, disease-free survival, recurrence rate, perioperative mortality, and morbidity.Expert commentary: This paper offers an overview of the results that are currently obtained in patients undergoing extrapleural pneumonectomy for MPM. The benefit of surgical treatments in MPM is still debated and its primary goal should be the achievement of a macroscopic complete resection. Several alternative multimodality protocols exist, with specific advantages and drawbacks; therefore, individualization of care for each patient is fundamental. The complexity of the surgical treatment mandates that patients be referred to specialized centers.

High systemic immune-inflammation index represents an unfavorable prognosis of malignant pleural mesothelioma

Background: Malignant pleural mesothelioma (MPM) represents a fatal disease with high aggressiveness, and limited biomarkers have yet been identified for MPM. The present study aims to explore potential serum prognostic factors of MPM.

Materials and methods: A retrospective analysis of 97 pathologically diagnosed MPM was performed. The optimal cutoff value of pretreatment systemic immune–inflammation index (SII) was determined by receiver operating characteristic curve. Kaplan–Meier curves and Cox regression analysis were performed to assess the potential prognostic roles of parameters.

Results: A total of 59.8% (n=58) patients are male, with a median age of 56.0 years (range 18–77). The optimal cutoff value of SII was 988.6×10⁹/L. High and low SII were found in 44 (45.4%) and 53 (54.6%) patients, respectively. Median survival time for total 97 cases was 18.5 months. The median overall survival for patients with low and high SII was 47.0 and 13.0 months, respectively. The 1-, 2- and 3-year survival rates for patients with low SII were 85.8%, 57.8% and 52.0% compared to that of 53.9%, 23.6% and 13.8% in patients with high SII. On univariate analysis, Eastern Cooperative Oncology Group performance status (ECOG PS)<2 points, low SII and adjuvant treatment (P<0.05) were found to be closely correlated with a better prognosis of MPM. Only ECOG PS (P=0.036) and SII (P=0.009) held statistical significance on multivariate analysis.

Conclusion: Pretreatment SII is easy to access to, and it represents an efficiency and noninvasive biomarker of MPM. High SII represents an unfavorable independent prognostic factor of MPM, and this needs to be validated in further studies.