How often should imaging be performed for intraductal papillary mucinous neoplasms (IPMNs) of the pancreas?

Imaging Frequency for Intraductal Papillary Mucinous Neoplasms (IPMNs) of the Pancreas

Patients with IPMNs should undergo lifelong surveillance with MRI as the preferred imaging modality, with follow-up intervals of 6 months for the first 2 years and annually thereafter for as long as the patient remains fit for surgery. 1

Risk Stratification and Imaging Intervals

Main Duct and Mixed-Type IPMNs

• Patients with main duct IPMN (MD-IPMN) or mixed-type IPMN who are fit for surgery should undergo resection due to high malignancy risk (56-91%) 1
• After resection of MD-IPMN or mixed-type IPMN with high-grade dysplasia, follow-up should occur every 6 months for the first 2 years, then yearly thereafter 1

Branch Duct IPMNs (BD-IPMNs)

• For BD-IPMNs without high-risk features:
  • Initial follow-up at 6 months 1
  • If stable, imaging every 6-12 months for the first 2 years 1, 2
  • After 2 years of stability, annual imaging is recommended 2
• For BD-IPMNs with worrisome features (cyst ≥3 cm, thickened/enhancing walls, MPD 5-9 mm):
  • More frequent follow-up every 3-6 months is recommended 1

Post-Surgical Follow-up

• Patients with IPMN-associated invasive carcinoma should be followed as per pancreatic cancer protocols 1
• Patients with resected IPMN with high-grade dysplasia require close follow-up every 6 months for 2 years, then yearly 1
• Patients with resected IPMN with low-grade dysplasia should be followed as per non-resected IPMN protocols 1

Imaging Modalities

• MRI with MRCP is the preferred imaging modality for IPMN follow-up due to superior characterization of ductal communication and internal architecture 1
• CT can be used as an alternative when MRI is contraindicated or unavailable 1
• EUS should be used selectively, particularly when there are concerning features requiring tissue sampling 1

Duration of Surveillance

• Surveillance should continue lifelong as long as the patient remains fit for surgery 1
• The risk of IPMN progression increases over time, with malignant transformation risk of approximately 0.24% per year 1
• Even after partial pancreatectomy for IPMN, lifelong follow-up is indicated due to risk of new lesions in the remnant pancreas 1

Risk Factors Requiring More Intensive Surveillance

• Presence of mural nodules (≥5 mm) 1, 3
• Main pancreatic duct dilation ≥5 mm 1
• Cyst size ≥40 mm 1
• Growth rate ≥5 mm/year or total growth of 10 mm 1
• Elevated serum CA 19-9 (>37 U/mL) 1

Special Considerations

• For undefined cysts <15 mm with no risk factors, re-examination after 1 year is recommended; if stable for 3 years, follow-up may be extended to every 2 years 1
• For undefined cysts ≥15 mm, follow-up every 6 months during the first year and annually thereafter is recommended 1
• Organ transplant recipients with IPMN should undergo the same surveillance protocol as non-transplanted patients 1

Pitfalls to Avoid

• Do not discontinue surveillance even after years of stability, as the risk of malignant progression increases over time 1
• Do not rely solely on cyst size for risk assessment; consider multiple risk factors including growth rate, mural nodules, and MPD dilation 1, 4
• Do not use the same follow-up protocol for all types of IPMNs; tailor the approach based on IPMN subtype and risk factors 1
• Do not neglect surveillance of the remnant pancreas after partial pancreatectomy for IPMN 1