What is the management approach for patients with multiple intrapulmonary mucinous neoplasms (IPMNs)?

Management of Multiple Intraductal Papillary Mucinous Neoplasms (IPMNs)

Management of multiple IPMNs should follow a risk-stratified approach with main duct and mixed-type IPMNs requiring surgical resection, while branch duct IPMNs without high-risk features can be managed with surveillance imaging. 1, 2

Risk Stratification and Initial Management

Main Duct and Mixed-Type IPMNs

• Main duct IPMNs (MD-IPMNs) and mixed-type IPMNs should be surgically resected in patients fit for surgery due to high malignancy risk (56-91%) 2
• Approximately 74% of patients with MD-IPMNs and mixed-type IPMNs should undergo primary resection 3
• The pancreatobiliary subtype of IPMN carries the highest risk of malignant transformation (67.9%) and should be prioritized for resection 4

Branch Duct IPMNs (BD-IPMNs)

• BD-IPMNs without high-risk features can be managed conservatively with surveillance 1
• Only 27.8% of BD-IPMNs require primary resection, with the risk of malignant transformation for BD-IPMNs smaller than 20mm being only 2% during follow-up 3
• Gastric subtype of BD-IPMNs has the lowest risk of invasion (10.2%) and can be managed more conservatively 4

High-Risk Features Requiring Surgical Intervention

• Presence of mural nodules ≥5 mm 2
• Main pancreatic duct dilation ≥5 mm 2
• Cyst size ≥40 mm 2
• Growth rate ≥5 mm/year or total growth of 10 mm 2
• Elevated serum CA 19-9 (>37 U/mL) 2
• New-onset diabetes mellitus 1

Surgical Considerations for Multiple IPMNs

• The extent of resection should be determined based on the location of high-risk lesions 1
• Be aware that pancreatic head resection for IPMNs carries higher risk of postoperative pancreatic fistula compared to resection for pancreatic ductal adenocarcinoma (36% vs 18.6%) 3
• For multifocal IPMNs, partial pancreatectomy targeting the highest-risk lesions is preferred over total pancreatectomy to preserve pancreatic function when possible 1
• Histopathological examination should assess the degree of dysplasia and presence/absence of invasive carcinoma 1

Surveillance Protocol After Initial Management

For Non-Resected BD-IPMNs

• Initial follow-up at 6 months, and if stable, imaging every 6-12 months for the first 2 years 2
• For BD-IPMNs with worrisome features, more frequent follow-up every 3-6 months is recommended 2
• For undefined cysts <15 mm with no risk factors, re-examination after 1 year; if stable for 3 years, follow-up may be extended to every 2 years 2

Post-Resection Surveillance

• 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 2
• Lifelong surveillance is recommended for patients with remnant pancreas after partial pancreatectomy due to risk of metachronous lesions 1, 2

Imaging Modalities for Surveillance

• MRI with MRCP is the preferred imaging modality for IPMN follow-up due to superior characterization of ductal communication and internal architecture 2
• CT can be used as an alternative when MRI is contraindicated or unavailable 2
• EUS should be used selectively, particularly when there are concerning features requiring tissue sampling 2

Prognostic Considerations

• Five-year overall survival rates differ significantly by IPMN type: MD-IPMN (44%), mixed-type IPMN (86%), and BD-IPMN (97.4%) 3
• Patients with invasive IPMN have worse survival than those with non-invasive dysplasia (33% vs 63-100% 5-year overall survival) 3
• The colloid carcinoma subtype of invasive IPMN has better 5-year survival (83%) compared to tubular carcinoma (24%) 5
• Conditional survival analysis shows that patients with initially high-risk disease who survive 4-5 years may actually have better subsequent survival prospects than those with lower-risk disease 6

Important Pitfalls to Avoid

• Do not discontinue surveillance even after years of stability, as the risk of malignant progression increases over time 2
• Do not rely solely on cyst size for risk assessment; consider multiple risk factors including growth rate, mural nodules, and MPD dilation 2
• Do not use the same follow-up protocol for all types of IPMNs; tailor the approach based on IPMN subtype and risk factors 2
• Do not neglect surveillance of the remnant pancreas after partial pancreatectomy for IPMN 1, 2
• Be aware that patients with IPMNs may have an increased risk of developing malignancies in other organs, such as the colon or stomach 1