What is the best treatment approach for a patient with peritoneal carcinomatosis?

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Last updated: January 8, 2026 • View editorial policy

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Treatment of Peritoneal Carcinomatosis

Primary Treatment Recommendation by Cancer Type

For gastric cancer with peritoneal carcinomatosis, systemic chemotherapy is the standard treatment, but cytoreductive surgery (CRS) plus hyperthermic intraperitoneal chemotherapy (HIPEC) should be offered to highly selected patients with limited disease burden (PCI ≤10) at specialized centers. 1, 2

For colorectal cancer with peritoneal carcinomatosis, complete cytoreductive surgery plus systemic chemotherapy WITHOUT HIPEC is recommended based on the PRODIGE 7 trial, which demonstrated no survival benefit and increased late complications with HIPEC addition. 3

Gastric Cancer Peritoneal Carcinomatosis

Patient Selection Algorithm

Step 1: Performance Status Assessment

  • ECOG PS ≥3 or Karnofsky <60%: Offer best supportive care only 2
  • ECOG PS 0-2: Proceed to disease burden assessment 2

Step 2: Disease Burden Stratification

  • Low PCI (≤10): Candidate for systemic therapy followed by potential CRS + HIPEC 1
  • High PCI (>10): Systemic therapy, clinical trial, or best supportive care only 1

Step 3: Initial Systemic Therapy (Minimum 3 Months)

  • Perform molecular testing: HER2, PD-L1 (CPS ≥1), CLDN18.2 (≥75% positive), MSI/MMR status 1, 2
  • Consider next-generation sequencing via validated assay 2
  • Administer systemic therapy based on molecular profile 1

Step 4: Re-staging After Systemic Therapy

  • Multidisciplinary discussion required for patients with: 1
    • Low PCI (≤10)
    • Improved or stable disease
    • No extraperitoneal metastases
    • Good performance status maintained

Step 5: CRS + HIPEC Candidacy Criteria

  • PCI <6-7 (some guidelines accept ≤10) 1, 2
  • Complete cytoreduction (R0 resection) achievable 2
  • No extraperitoneal unresectable metastases 2
  • Good performance status maintained 2
  • Treatment at specialized center with substantial experience 2

Survival Outcomes for Gastric Cancer

  • CRS + HIPEC: Median overall survival 11-24 months 2
  • CRS alone: Median overall survival 6.5 months 2
  • Systemic chemotherapy alone: Median overall survival 5-6 months 1, 2

Colorectal Cancer Peritoneal Carcinomatosis

Evidence-Based Treatment Algorithm

The PRODIGE 7 trial definitively established that HIPEC provides no survival benefit (HR 1.00; 95% CI 0.63-1.58) and increases late complications (RR 1.69; 95% CI 1.03-2.77). 3

Step 1: Confirm Isolated Peritoneal Disease

  • No extraperitoneal metastases 3
  • Diagnostic laparoscopy recommended for accurate staging (sensitivity 85%, specificity 100%) 1, 4

Step 2: Neoadjuvant Systemic Chemotherapy

  • Based on molecular characteristics (RAS, BRAF, MSI status) 3
  • Assess response and resectability 3

Step 3: Complete Cytoreductive Surgery WITHOUT HIPEC

  • Only if complete macroscopic cytoreduction (CC-0) achievable 3
  • Completeness of cytoreduction is the most critical prognostic factor 3
  • Treatment at specialized center with substantial CRS experience mandatory 3

Step 4: Adjuvant Systemic Chemotherapy

  • Continue systemic therapy post-operatively 3

Survival Outcomes for Colorectal Cancer

  • 15% of patients remain progression-free at 5 years with complete CRS 3
  • Mortality rate related to CRS treatment: 8% in historical studies 3

Ovarian Cancer Peritoneal Carcinomatosis

Complete cytoreductive surgery is the cornerstone of treatment, with some data supporting possible benefit of HIPEC addition in first-line and relapsed settings. 1

  • Optimal cytoreduction with peritonectomy should be pursued 1
  • HIPEC may be considered but is not definitively established 1
  • Treatment at specialized centers with low PCI and good performance status 1

Cancer of Unknown Primary (CUP) with Peritoneal Carcinomatosis

Treatment Based on Suspected Primary

Ovary-like CUP or Colon-like CUP (mucin-producing/signet ring):

  • Assessment for cytoreductive surgery with peritonectomy is an option 1
  • HIPEC is NOT recommended due to lack of data 1
  • Strict patient selection: good PS, low PCI, no extraperitoneal disease 1

Unfavorable CUP:

  • Peritonectomy is NOT recommended 1
  • Consider immunotherapy if TMB-high (≥10 mut/Mb) or PD-L1-high 1

Novel and Palliative Approaches

Pressurized Intraperitoneal Aerosol Chemotherapy (PIPAC)

  • Median overall survival: 15 months 2
  • Should ONLY be performed within clinical trials 2
  • Reserved for patients not candidates for CRS + HIPEC 2

Symptom-Directed Interventions

  • Malignant ascites: Paracentesis for symptom relief (cytology sensitivity 96.7% with three samples) 4, 5
  • Gastric outlet obstruction: Palliative gastrojejunostomy or endoscopic stenting 2
  • Early palliative care involvement: Essential for holistic symptom management 5

Critical Pitfalls to Avoid

1. Overestimating Disease Burden with CT Imaging

  • CT sensitivity for peritoneal metastases is only 28-51% (specificity 97-99%) 1, 4
  • Diagnostic laparoscopy is superior (sensitivity 85%, specificity 100%) 1, 4
  • PET-CT detects only 3% of occult peritoneal metastases 1

2. Offering CRS + HIPEC to Unselected Patients

  • Restrict to PCI <6-7 (gastric) or achievable complete cytoreduction (colorectal) 1, 2, 3
  • Requires specialized center with substantial experience 2, 3
  • High morbidity/mortality risk (8% treatment-related mortality) 3

3. Adding HIPEC to Colorectal CRS

  • PRODIGE 7 definitively showed no benefit and increased complications—HIPEC should NOT be used for colorectal peritoneal carcinomatosis 3

4. Pursuing Reduction Surgery Based on Outdated Evidence

  • REGATTA trial showed no benefit for palliative gastrectomy in gastric cancer 2
  • Abandon this approach outside highly exceptional circumstances 2

5. Performing PIPAC or Experimental Intraperitoneal Chemotherapy Outside Clinical Trials

  • Lack definitive evidence—restrict to research settings 2

6. Failing to Assess Molecular Markers

  • HER2, PD-L1, CLDN18.2, MSI/MMR testing essential for systemic therapy selection in gastric cancer 1, 2
  • RAS, BRAF, MSI testing essential for colorectal cancer 3

7. Relying on Negative Ascitic Fluid Cytology

  • Negative cytology does not exclude peritoneal carcinomatosis, especially in low-volume disease 4

8. Inadequate Patient Selection for CRS

  • Complete macroscopic cytoreduction (CC-0) is the decisive factor for long-term survival 3
  • Only 1 of 18 patients with complete resection died after median follow-up of 21.6 months 3

Multidisciplinary Team Requirements

Mandatory team composition for CRS consideration: 3

  • Medical oncology expertise
  • Surgical oncology with substantial CRS experience
  • Radiology (preferably with laparoscopy capability)
  • Pathology
  • Palliative care specialists 5

References

1
Guideline

Guideline Directed Topic Overview

Dr.Oracle Medical Advisory Board & Editors, 2025

2
Guideline

Management of Gastric Cancer with Peritoneal Carcinomatosis

Praxis Medical Insights: Practical Summaries of Clinical Guidelines, 2025

3
Guideline

PRODIGE 7 Trial: Key Findings and Clinical Implications

Praxis Medical Insights: Practical Summaries of Clinical Guidelines, 2025

4
Guideline

Diagnosis of Peritoneal Carcinomatosis

Praxis Medical Insights: Practical Summaries of Clinical Guidelines, 2025

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Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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