Residency · Residency · Cardiothoracic Surgery
Mesothelioma: Diagnosis and Surgical Options
Overview
Malignant pleural mesothelioma (MPM) is an aggressive neoplasm arising from mesothelial cells of the pleura with a strong association with asbestos exposure (latency period 20-50 years). Median survival without treatment is 9-12 months. Multimodal therapy (surgery plus chemotherapy with or without radiation) may improve outcomes in selected patients, though the role of radical surgery remains highly controversial following the MARS and MARS-2 trial results.
Epidemiology and Etiology
The incidence is approximately 3,000 cases per year in the United States, with declining rates in some countries but rising in others due to historical asbestos use patterns. There is a marked male predominance (4:1) reflecting occupational asbestos exposure. Asbestos fibers include chrysotile (white, serpentine) and amphibole types (crocidolite, amosite — the most carcinogenic). Other risk factors include erionite (a volcanic fiber found in Turkey), radiation therapy, SV40 virus (debated), and genetic predisposition through BAP1 germline mutations. Non-asbestos mesothelioma is increasingly recognized, especially in younger patients with BAP1 mutations.
Histologic Subtypes
Epithelioid mesothelioma (60%) carries the best prognosis and is the most amenable to multimodal therapy. Sarcomatoid (10-15%) has the worst prognosis, responds poorly to therapy, and generally does not benefit from surgery. Biphasic (mixed) (25-30%) carries an intermediate prognosis, with outcomes influenced by the proportion of sarcomatoid component. Histology is confirmed by immunohistochemistry: positive markers include calretinin, WT-1, CK5/6, and D2-40, while negative markers (CEA, TTF-1, BerEP4, MOC-31) help exclude adenocarcinoma.
Mesothelioma Histologic Subtypes
| Subtype | Frequency | Prognosis | Surgical Candidacy | Key Feature |
|---|---|---|---|---|
| Epithelioid | 60% | Best | Most amenable to multimodal therapy | IHC: calretinin+, WT-1+, CK5/6+, D2-40+ |
| Sarcomatoid | 10-15% | Worst | Generally not offered radical surgery | Poor response to all therapies |
| Biphasic (mixed) | 25-30% | Intermediate | Depends on sarcomatoid proportion | Prognosis worsens with higher sarcomatoid % |
Staging (AJCC 8th Edition / IMIG)
T Classification
T1 tumors are limited to the ipsilateral parietal pleura (with or without visceral, mediastinal, or diaphragmatic pleura). T2 involves the ipsilateral pleura with at least one of: confluent visceral pleural tumor, diaphragmatic muscle invasion, or pulmonary parenchymal invasion. T3 is locally advanced but potentially resectable, involving the endothoracic fascia, mediastinal fat, solitary chest wall focus, or non-transmural pericardium. T4 is unresectable locally advanced disease with diffuse or multifocal chest wall invasion, peritoneal involvement, contralateral pleura, spine, internal surface of pericardium, myocardium, or brachial plexus.
N Classification
N0 indicates no regional lymph node metastasis. N1 indicates ipsilateral bronchopulmonary, hilar, or mediastinal nodes. N2 indicates contralateral mediastinal, internal mammary, or supraclavicular nodes.
Stage Groupings
Stage IA is T1 N0 M0. Stage IB is T2-T3 N0 M0. Stage II is T1-T2 N1 M0. Stage IIIA is T3 N1 M0. Stage IIIB includes T1-T3 N2 or T4 any N M0. Stage IV is any M1.
<image>IMIG staging diagram for malignant pleural mesothelioma showing T descriptors with progressive pleural and chest wall involvement</image>
Diagnostic Workup
Clinical Presentation
Dyspnea is the most common presenting symptom, accompanied by chest pain, cough, and weight loss. Imaging reveals a unilateral pleural effusion with pleural thickening that is often nodular and circumferential. Progressive encasement and restriction of the lung creates a "trapped lung."
Imaging
CT chest with contrast demonstrates nodular pleural thickening, pleural effusion, fissural thickening, and volume loss. PET-CT provides staging, lymph node assessment, and detection of occult metastatic disease, with SUV correlating with prognosis. MRI is superior for assessment of diaphragmatic and chest wall invasion.
Tissue Diagnosis
Thoracentesis with cytology has a sensitivity of only 30-50% and is insufficient for diagnosis in most cases. VATS pleural biopsy is the gold standard, allowing direct visualization, multiple biopsies, and pleurodesis. CT-guided pleural biopsy is an alternative when VATS is not feasible. Histologic confirmation with immunohistochemistry is mandatory.
Surgical Options
Extrapleural Pneumonectomy (EPP)
EPP is a radical resection involving en bloc removal of the visceral and parietal pleura, ipsilateral lung, ipsilateral pericardium, and ipsilateral diaphragm, with reconstruction of the pericardium and diaphragm using prosthetic patches. Operative mortality is 5-10% in experienced centers, and morbidity reaches 50-60% (atrial fibrillation, pneumonia, empyema, patch dehiscence, ARDS). EPP has largely fallen out of favor following the MARS trial and subsequent data showing high mortality without clear survival benefit.
Pleurectomy/Decortication (P/D)
P/D aims for macroscopic complete resection (MCR) of all visible tumor through parietal and visceral pleurectomy with or without diaphragm and pericardium resection. Extended P/D includes diaphragm and/or pericardium resection, while standard P/D involves the pleura only. This lung-sparing operation preserves the ipsilateral lung, carries operative mortality of 2-4% (lower than EPP), and offers better preservation of pulmonary function and quality of life. P/D is the current preferred surgical approach when surgery is offered.
EPP vs. P/D Comparison
| Feature | Extrapleural Pneumonectomy (EPP) | Pleurectomy/Decortication (P/D) |
|---|---|---|
| Structures removed | Pleura, lung, pericardium, diaphragm | Pleura (± pericardium, diaphragm) |
| Lung preserved | No | Yes |
| Operative mortality | 5-10% | 2-4% |
| Morbidity | 50-60% | Lower |
| Pulmonary function | Significantly impaired | Better preserved |
| Current role | Largely abandoned (MARS trial) | Preferred if surgery offered |
| R0 resection | Higher MCR rate (theoretical) | MCR achievable |
Partial Pleurectomy / Debulking
Partial pleurectomy is a palliative procedure with incomplete tumor removal for symptom control, often combined with talc pleurodesis to prevent re-accumulation of effusion. Oncologic benefit is limited.
<image>Comparison of extrapleural pneumonectomy (EPP) and pleurectomy/decortication (P/D) showing extent of resection and structures removed in each approach</image>
Key Trial Evidence
MARS Trial (2011)
This feasibility RCT examined EPP within multimodal therapy versus no EPP. Only 50 patients were randomized from 112 registered. The EPP arm showed higher mortality (12.5% operative mortality) with no survival benefit. Median survival was 14.4 months with EPP versus 19.5 months without. The conclusion was that EPP within trimodality therapy offers no benefit and is potentially harmful. The trial has been criticized for its small sample size and feasibility design, which was not powered for survival.
MARS-2 Trial (2024)
This RCT examined extended P/D within multimodal therapy versus chemotherapy alone, enrolling 335 patients. There was no improvement in overall survival with extended P/D (median OS 19.3 months versus 24.8 months with chemotherapy alone). Thirty-day mortality was higher in the surgical arm, and quality of life outcomes were initially worse. The conclusion was that extended P/D does not improve survival over chemotherapy alone, significantly challenging the role of radical surgery for mesothelioma.
Key Mesothelioma Trials
| Trial | Design | Key Finding |
|---|---|---|
| MARS (2011) | RCT: EPP vs. no EPP (n=50 randomized) | No survival benefit; EPP harmful (12.5% operative mortality) |
| MARS-2 (2024) | RCT: Extended P/D vs. chemo alone (n=335) | No OS benefit with P/D (19.3 vs. 24.8 months) |
| EMPHACIS (2003) | RCT: Cisplatin-pemetrexed vs. cisplatin | OS benefit (12.1 vs. 9.3 months); established first-line chemo |
| MAPS (2016) | RCT: Added bevacizumab to chemo | OS benefit (18.8 vs. 16.1 months) |
| CheckMate 743 (2020) | RCT: Nivolumab-ipilimumab vs. chemo | OS benefit (18.1 vs. 14.1 months); now first-line for unresectable MPM |
Interpretation and Ongoing Debate
Both trials have been criticized for methodologic limitations. Single-institution retrospective series continue to show survival benefit from surgery in selected patients. Patient selection remains the critical variable, focusing on epithelioid histology, minimal N2 disease, and low tumor volume. Surgery may benefit a highly select subset, but broad application is not supported.
Multimodal Treatment Approaches
Chemotherapy
First-line therapy is cisplatin plus pemetrexed, based on the EMPHACIS trial (2003), which showed median OS of 12.1 months versus 9.3 months with cisplatin alone. The addition of bevacizumab (MAPS trial) showed an OS benefit (18.8 versus 16.1 months). Nivolumab plus ipilimumab (CheckMate 743, 2020) is now first-line for unresectable MPM, with OS benefit especially in non-epithelioid histology (median OS 18.1 versus 14.1 months).
Radiation Therapy
Prophylactic radiation to procedure tract sites is controversial, with recent trials showing no benefit. Adjuvant hemithoracic radiation after EPP follows the SMART protocol (short-course accelerated RT then EPP). Intensity-modulated pleural radiation therapy (IMPRINT) after P/D provides lung-sparing radiation. The role of radiation in the post-MARS-2 era is uncertain.
Hyperthermic Intrathoracic Chemotherapy (HITHOC)
HITHOC delivers intrapleural heated chemotherapy (cisplatin) at the time of P/D, with the rationale of direct cytotoxic effect on residual microscopic disease. Evidence is limited to single-institution studies, with phase II data suggesting feasibility but phase III data lacking.
<image>Algorithm for treatment decision-making in malignant pleural mesothelioma based on histology, staging, and functional status</image>
Palliative Management
An indwelling pleural catheter (IPC) is effective for recurrent symptomatic effusions. Talc pleurodesis achieves chemical pleurodesis via VATS or bedside slurry. Pain management includes intercostal nerve blocks and radiation for chest wall pain. Palliative systemic therapy provides symptom control.
Prognosis
Overall median survival is 12-18 months. Favorable prognostic factors include epithelioid histology, early stage, female sex, young age, good performance status, and no weight loss. EORTC and CALGB prognostic scores stratify patients into risk groups. Long-term survivors (greater than 5 years) exist but are rare; most have epithelioid histology, early stage, and complete surgical resection.
Clinical Pearls
Mesothelioma is a diagnosis of exclusion — always confirm with an immunohistochemistry panel to differentiate from pleural adenocarcinoma metastasis. Cytology alone from thoracentesis is insufficient for diagnosis in most cases, and pleural biopsy is required. Following MARS-2, the routine use of radical surgery for mesothelioma is no longer supported by RCT evidence. If surgery is considered, it should be in the context of a clinical trial or at an experienced high-volume center. Sarcomatoid mesothelioma should generally not be offered radical surgery because prognosis is poor regardless. Nivolumab plus ipilimumab is now first-line for unresectable mesothelioma (CheckMate 743). BAP1 germline mutations should be considered in young patients or those with a family history of mesothelioma, uveal melanoma, or renal cell carcinoma.
References
- Treasure T et al. "Extra-pleural pneumonectomy versus no extra-pleural pneumonectomy for patients with malignant pleural mesothelioma (MARS)." Lancet Oncol. 2011.
- Lim E et al. "Extended pleurectomy decortication versus chemotherapy for mesothelioma (MARS-2)." Lancet. 2024.
- Vogelzang NJ et al. "Cisplatin and pemetrexed for malignant pleural mesothelioma (EMPHACIS)." J Clin Oncol. 2003.
- Baas P et al. "First-line nivolumab plus ipilimumab in unresectable malignant pleural mesothelioma (CheckMate 743)." Lancet. 2021.
- Zalcman G et al. "Bevacizumab for newly diagnosed pleural mesothelioma (MAPS)." Lancet. 2016.
- Rusch VW et al. "The IASLC Mesothelioma Staging Project." J Thorac Oncol. 2016.
