What happens when pancreatic cancer metastasizes to the liver, and how is it indicated on a computed tomography (CT) scan?

Pancreatic Cancer with Liver Metastases: Clinical Implications and CT Imaging Findings

When pancreatic cancer spreads to the liver, it represents Stage IV metastatic disease that is unresectable and requires palliative systemic chemotherapy, with a median survival typically measured in months rather than years. 1

Clinical Significance of Hepatic Metastases

Liver metastases from pancreatic cancer fundamentally change the treatment approach from curative intent to palliative care. 1 The presence of hepatic metastases:

• Renders the cancer surgically unresectable, eliminating the only potentially curative treatment option 1
• Shifts treatment goals to palliation of symptoms including pain, jaundice, duodenal obstruction, and weight loss 1
• Indicates advanced disease with poor prognosis, as pancreatic cancer shows remarkable preference for hepatic metastasis 2

The liver is one of the most common sites for pancreatic cancer metastasis, and detection of liver lesions during staging workup occurs in a substantial proportion of patients at initial presentation. 1

CT Scan Findings of Liver Metastases

On CT imaging, pancreatic cancer liver metastases typically appear as hypovascular (low-density) masses within the liver parenchyma on contrast-enhanced multiphasic CT. 3 The optimal CT protocol for detection includes:

Technical Imaging Requirements

• Multiphasic contrast-enhanced CT with late arterial/pancreatic phase (40-50 seconds post-contrast) and portal venous phase (70 seconds post-contrast) 3
• Thin-slice acquisition with submillimeter axial sections for optimal detection 3
• Non-ionic iodinated contrast agent at 1.5 ml/kg injected at 4-5 ml/s 1, 3

Appearance of Metastatic Lesions

• Hypovascular (hypodense) masses scattered throughout the liver parenchyma, appearing darker than normal liver tissue on contrast-enhanced phases 1, 4
• Multiple lesions are common, though solitary metastases can occur 5, 4
• Variable sizes ranging from small (<1 cm) to large masses (several centimeters) 1

Important Diagnostic Considerations

CT may miss small liver metastases that are visible on MRI. 1 According to ESMO guidelines, MRI with diffusion-weighted sequences identifies liver metastases not visible on CT in 10-23% of cases, potentially reducing unnecessary laparotomy in patients thought to have resectable disease. 1 This is particularly important because:

• MRI is more sensitive than CT for detecting small hepatic lesions 1
• Laparoscopy can detect small peritoneal and liver metastases missed by CT in up to 25% of patients, changing therapeutic strategy 1
• Staging laparoscopy should be considered before resection in left-sided large tumors or when CA19-9 levels are markedly elevated 1

Pathological Confirmation

When liver metastases are present, biopsy is mandatory before initiating chemotherapy. 1 The metastatic lesions can be biopsied:

• Percutaneously under ultrasound or CT guidance 1
• During EUS if technically feasible 1
• During laparoscopy if performed for staging 1

Histopathological examination typically confirms moderately to poorly differentiated adenocarcinoma consistent with pancreatic origin. 4 Immunohistochemical staining shows positivity for CK7 and negativity for CK20, CDX2, and SATB2, distinguishing pancreatic from colorectal primary tumors. 4

Treatment Implications

The presence of liver metastases mandates palliative systemic chemotherapy rather than surgical resection. 1 Treatment options include:

• FOLFIRINOX (leucovorin, 5-fluorouracil, irinotecan, oxaliplatin) for fit patients, which can produce dramatic responses in select cases 5, 4
• Gemcitabine-based regimens as alternative first-line therapy 1
• Palliative interventions for symptom management including endoscopic stenting for biliary obstruction (metal stents preferred for life expectancy >3 months) and opioids for pain control 1, 6

Rare Exception: Conversion to Resectability

In exceptional cases (<1%), dramatic response to systemic chemotherapy can result in complete regression of liver metastases, potentially allowing subsequent surgical resection of the primary tumor. 5 However, this represents an extraordinarily rare outcome and should not be expected as standard practice. 5, 7

Critical Pitfalls to Avoid

• Do not rely solely on CT for staging when surgical resection is being considered, as MRI detects additional liver metastases in 10-23% of cases 1
• Do not proceed with surgery if liver metastases are confirmed, as this provides no survival benefit and increases morbidity 1
• Do not delay biopsy in metastatic disease, as pathological confirmation is mandatory before initiating chemotherapy 1
• Do not use PET-CT as primary staging modality, though it may be considered after formal pancreas protocol CT in select high-risk patients 3