22Mesothelioma & peritoneal surface
Snapshot. Cancer of the mesothelial lining. PLEURAL (~80%) — asbestos, older men — vs PERITONEAL — younger, often non-asbestos, more women. Histology sets prognosis: epithelioid (best) · biphasic · sarcomatoid (worst). BAP1 loss is characteristic (+ a germline cancer syndrome). KEY TRAP: peritoneal disease looks "metastatic" on scans but is usually PERITONEUM-CONFINED — which makes it a candidate for CYTOREDUCTIVE SURGERY, not automatically incurable. ⚠ DDx of a mucinous peritoneal picture = PSEUDOMYXOMA PERITONEI (appendiceal mucinous; CK20/CDX2/MUC2, NOT calretinin) — a different disease, but also treated by CRS+HIPEC.
Workup
CT chest/abdomen/pelvis ± MRI ± PET · CORE or SURGICAL biopsy — effusion cytology ALONE is insufficient (need architecture + IHC) · IHC: calretinin · WT1 · D2-40 · CK5/6 positive; BAP1 loss (separates it from adenocarcinoma) · asbestos + family history (BAP1 syndrome) · performance status + resectability judged by a peritoneal-surface-malignancy / HIPEC team.
Treatment by setting
| Setting | Treatment |
|---|
PLEURAL — resectable
early, epithelioid, fit — highly selected | Multimodal at an expert centre — lung-sparing pleurectomy/decortication (P/D) + systemic chemo ± radiotherapy ⚠ Surgery's role is controversial
MARS-2: adding extrapleural pneumonectomy did not help — centre- and patient-specific |
PLEURAL — unresectable / metastatic
1st line | Nivolumab + ipilimumab (CheckMate-743)
first new standard in ~15 yr · biggest benefit in NON-epithelioid OR cisplatin (or carboplatin) + PEMETREXED ± bevacizumab
pembrolizumab + chemo is an alternative · ⚠ pemetrexed needs folate + B12 |
PERITONEAL — peritoneum-confined
resectable, adequate PS | CYTOREDUCTIVE SURGERY (CRS) + HIPEC
hyperthermic intraperitoneal chemotherapy — potentially long survival, NOT palliative; the option systemic chemo alone misses · ± perioperative systemic chemo 🔴 "Metastatic-looking" peritoneal disease deserves a surface-malignancy opinion BEFORE it is called incurable |
PERITONEAL — unresectable
multi-compartment (e.g. + pleural/skin), poor PS, or refractory | Systemic — platinum + pemetrexed, or nivolumab + ipilimumab
the IO doublet is active in peritoneal meso too Best supportive / palliative care
where multi-compartment or refractory ⚠ Mesothelioma SEEDS biopsy + drain tracts |
Watch
Pemetrexed → myelosuppression, mucositis, rash — mandatory FOLIC ACID + B12. Cisplatin → nephro/oto/neurotoxicity. Nivolumab + ipilimumab → immune-related adverse events (colitis, hepatitis, pneumonitis, endocrinopathy). Tract seeding — meso implants along instrumented sites. BAP1 germline → counsel + screen for uveal/cutaneous melanoma + renal cell carcinoma.