Peritoneal Carcinomatosis: Causes, Symptoms, Diagnosis and Treatment — Overview, Diagnosis & Treatment Options | MyMedicPlus

Peritoneal carcinomatosis (peritoneal metastasis, PM) describes diffuse dissemination of malignant cells throughout the peritoneal cavity. It most commonly originates from colorectal cancer (~20% develop PM), ovarian cancer (>70% present with PM), gastric cancer (~40%), appendiceal mucinous neoplasms (pseudomyxoma peritonei), and mesothelioma. It represents Stage IV disease for most primary tumors.

Peritoneal metastasis occurs via direct transcoelomic spread — malignant cells exfoliate from the primary tumor and implant on peritoneal surfaces. Risk factors for PM depend on primary tumor: perforated or T4 colorectal cancer, mucinous colorectal histology, signet ring cell gastric cancer, advanced ovarian cancer, and ruptured appendiceal mucinous tumors (PMP). PM from hematogenous seeding also occurs.

Abdominal distension from malignant ascites, nausea, vomiting, small bowel obstruction (malignant ileus), diffuse abdominal pain, early satiety, anorexia, and progressive weight loss. Palpable omental 'cake' on examination. Performance status decline and nutritional compromise are prominent. Often presents as deterioration of a known malignancy rather than as a new diagnosis.

Contrast-enhanced CT abdomen/pelvis detects larger peritoneal deposits but misses sub-centimeter implants. Diffusion-weighted MRI has higher sensitivity. Diagnostic laparoscopy with systematic peritoneal biopsy and peritoneal cancer index (PCI) scoring — the essential tool for surgical planning. PCI scores 0-39 based on 13 abdominal regions and lesion size. Ascites cytology. Molecular profiling of primary/metastatic biopsy tissue.

Systemic chemotherapy per primary tumor primary oncologic type (FOLFOX/FOLFIRI for colorectal PM; carboplatin-taxane for ovarian; FLOT for gastric). For selected patients with limited peritoneal disease (low PCI): cytoreductive surgery (CRS) plus HIPEC at specialized centers — curative intent for colorectal, ovarian, appendiceal, and mesothelioma. PIPAC (pressurized intraperitoneal aerosol chemotherapy) for palliative peritoneal drug delivery. Bevacizumab for colorectal PM. Palliative paracentesis for symptomatic ascites.

Highly variable by primary tumor and extent (PCI). Optimal CRS/HIPEC for colorectal PM (PCI ≤20): median OS approximately 30-40 months. Ovarian PM with complete cytoreduction: median OS approximately 30-45 months. Gastric PM: median OS approximately 6-12 months even with chemotherapy. Unresectable colorectal PM: median OS approximately 12-16 months with modern systemic therapy. Pseudomyxoma peritonei with CRS/HIPEC: 10-year OS approximately 60-90%.