What Is Peritoneal Mesothelioma?
Peritoneal mesothelioma is a cancer of the peritoneum, the thin membrane lining the abdominal cavity and covering the abdominal organs. It accounts for about 11% of US mesothelioma diagnoses (7,079 of 63,620 cases between 2003 and 2022, per CDC US Cancer Statistics), making it the second most common form after pleural mesothelioma. Published cohort ranges run from 10% to 20% depending on registry and time period.
Unlike pleural mesothelioma, peritoneal mesothelioma has a significantly better prognosis. SEER reports a 65% 5-year relative survival for peritoneal disease compared to 12% for pleural. At high-volume centers, cytoreductive surgery with HIPEC produces 5-year survival of 47% to 52% in selected patients.
How Peritoneal Mesothelioma Develops
The Asbestos Exposure Pathway
Like all mesothelioma types, peritoneal mesothelioma is caused by asbestos exposure. The exact mechanism by which asbestos fibers reach the peritoneum is not fully understood, but researchers propose two pathways: ingestion (swallowed fibers travel through the digestive system and penetrate the peritoneal lining) and translocation (inhaled fibers migrate from the lungs through the lymphatic system to the abdomen). The latency period averages 20 to 50 years, similar to pleural mesothelioma.
Who Is at Risk
| Risk Factor | Details |
|---|---|
| Occupational asbestos exposure | Construction, shipyard, and industrial workers |
| Secondary exposure | Family members of asbestos workers |
| Environmental exposure | Living near asbestos mines or processing facilities |
| Gender | Unlike pleural, affects men and women more equally |
| Genetic factors | BAP1 gene mutations may increase susceptibility |
Symptoms of Peritoneal Mesothelioma
Symptoms develop gradually and are often mistaken for other abdominal conditions.
Early-Stage Symptoms
Later-Stage Symptoms
- Severe abdominal distension
- Bowel obstruction
- Difficulty eating
- Fatigue and weakness
- Night sweats
- Fever
- Anemia
Ascites: The Hallmark Symptom
Ascites, fluid buildup in the abdominal cavity, is the most characteristic symptom of peritoneal mesothelioma. It causes visible abdominal swelling, feeling of fullness, difficulty breathing (when fluid presses on diaphragm), and discomfort when sitting or lying down. Ascites often prompts patients to seek medical attention and leads to diagnosis.
Diagnosis
Diagnostic Process
The workup generally follows a consistent sequence. Clinicians start with medical history (including detailed occupational and exposure history) and a physical examination checking for abdominal swelling and tenderness. Imaging (CT, MRI, PET) characterizes tumor spread. Paracentesis removes and analyzes abdominal fluid, and a biopsy (via laparoscopy or laparotomy) provides a tissue sample. Immunohistochemistry is what ultimately distinguishes peritoneal mesothelioma from other abdominal cancers. Experienced centers such as the National Cancer Institute and MedStar Washington Hospital Center use dedicated mesothelioma pathology panels to reach a confident diagnosis.
Cell Types
| Cell Type | Frequency | Prognosis |
|---|---|---|
| Epithelioid | 75% | Best |
| Sarcomatoid | 10% | Poorest |
| Biphasic | 15% | Intermediate |
Peritoneal mesothelioma has a higher percentage of epithelioid cases than pleural, which partly explains better outcomes.
Staging: Peritoneal Cancer Index (PCI)
Peritoneal mesothelioma doesn’t use the standard TNM staging system. Instead, doctors use the Peritoneal Cancer Index (PCI):
Treatment Options
Cytoreductive Surgery with HIPEC
Cytoreductive surgery (CRS) combined with HIPEC (Hyperthermic Intraperitoneal Chemotherapy) is the gold standard treatment for peritoneal mesothelioma and offers the best survival outcomes.
How it works:
- Cytoreductive surgery: Surgeon removes all visible tumors from the abdominal cavity, including affected portions of the peritoneum and sometimes parts of organs
- HIPEC: Heated chemotherapy (104-109°F) is circulated directly in the abdomen for 60-90 minutes, killing microscopic cancer cells surgery couldn’t remove
Who Qualifies for CRS/HIPEC?
| Factor | Effect | Why It Matters |
|---|---|---|
| Lower PCI score | Improves candidacy | Less tumor burden |
| Epithelioid cell type | Improves candidacy | Better response to treatment |
| Good overall health | Improves candidacy | Better tolerance of surgery |
| No distant metastasis | Improves candidacy | Surgery can remove all disease |
| Younger age | Improves candidacy | Better recovery |
| Experienced center | Improves candidacy | Better surgical outcomes |
When Surgery Is Not an Option: Chemotherapy
For people who cannot undergo surgery, systemic chemotherapy is the primary treatment:
Pemetrexed with cisplatin can be used as primary treatment when surgery is not possible, or as neoadjuvant therapy before surgery to improve cytoreduction. It can shrink tumors and relieve symptoms even when long-term remission is unlikely.
Immunotherapy Options
Immunotherapy has become a treatment option for peritoneal mesothelioma. Nivolumab (Opdivo) plus ipilimumab (Yervoy) received FDA approval in 2020 for unresectable mesothelioma based on the CheckMate 743 trial. Although that trial focused on pleural disease, the combination is now used for unresectable peritoneal cases, sometimes alongside chemotherapy, and is often considered after recurrence following CRS plus HIPEC.
Palliative Approaches
For advanced cases, palliative treatments focus on quality of life. Paracentesis drains ascites fluid for comfort, multimodal pain management addresses abdominal pain, nutritional support counters cachexia, and broader symptom control keeps people at home rather than in the hospital when possible.
Survival Rates and Prognosis
| Treatment | Median Survival | 5-Year Survival |
|---|---|---|
| CRS + HIPEC | 53-92 months | 47-52% |
| Chemotherapy alone | 12-14 months | ~10% |
| No treatment | 6-8 months | <5% |
Factors Affecting Prognosis
| Prognostic Factor | Effect |
|---|---|
| Epithelioid cell type | Positive |
| Lower PCI score | Positive |
| Complete cytoreduction achieved | Positive |
| Treatment at high-volume HIPEC center | Positive |
| Good performance status | Positive |
| Female gender | Positive |
| Younger age | Positive |
| No lymph node involvement | Positive |
| Sarcomatoid or biphasic cell type | Negative |
| High PCI score | Negative |
| Incomplete cytoreduction | Negative |
| Lymph node metastasis | Negative |
Finding Specialized Treatment
HIPEC Centers
CRS/HIPEC is a complex procedure that should only be performed at experienced centers. Volume matters, centers performing more procedures have better outcomes.
Am I a candidate for CRS/HIPEC surgery?▼
Candidacy depends on PCI score, cell type (epithelioid preferred), overall health, and absence of distant metastasis. Evaluation at an experienced HIPEC center is essential. Center volume matters significantly for outcomes.
What is my PCI score?▼
The Peritoneal Cancer Index scores tumor burden across 13 abdominal regions (0-39 total). Lower scores indicate better surgical candidacy: PCI 0-20 has 103-month median survival vs 33 months for PCI 21-39.
How many HIPEC procedures has this center performed?▼
Volume matters. Look for high-volume centers with experienced surgical oncology teams. Centers performing more procedures have better outcomes and lower complication rates.
Are there clinical trials I might qualify for?▼
Yes, trials studying new immunotherapy combinations, targeted therapies, and novel drug delivery methods are enrolling. Ask your oncologist about trials you may qualify for at major mesothelioma centers.
Living with Peritoneal Mesothelioma
After HIPEC Surgery
| Aspect | What to Expect |
|---|---|
| Hospital stay | 1-2 weeks |
| Full recovery | 2-3 months |
| Dietary changes | May need modified diet initially |
| Follow-up | Regular imaging and check-ups |
Managing Symptoms After Treatment
Several areas need ongoing attention. Ascites may require periodic drainage through paracentesis or a tunneled catheter. Nutrition often improves with a dietitian’s input, especially after bowel resection. Pain control spans medications, nerve blocks, and low-dose radiation in selected cases. Emotional support through counseling and support groups helps people and families manage the long arc of recovery.
Clinical Trials
Patients should ask about clinical trials, which may offer access to:
- New immunotherapy combinations
- Targeted therapies
- Novel drug delivery methods
- Combination approaches