Laboratory Monitoring and Decision‑Making in Intraductal Papillary Mucinous Neoplasms (IPMN)

Baseline Laboratory Evaluation

Serum CA 19‑9 should be measured in every patient with radiologically suspected IPMN at the initial assessment; an elevation > 37 U/mL is strongly associated with invasive carcinoma and serves as a relative indication for surgical resection. 1, 2
The CA 19‑9 threshold of > 37 U/mL is applicable only in the absence of jaundice or biliary obstruction. 1, 2, 3
CA 19‑9 > 37 U/mL yields a positive predictive value of ≈ 74 % and an overall diagnostic accuracy of ≈ 81.7 % for identifying invasive IPMN. 1, 2

Fasting blood glucose and/or HbA1c should be obtained routinely during IPMN surveillance. 4
Development of new‑onset diabetes mellitus in a patient with IPMN is a relative indication for surgery and signals a higher risk of malignant transformation. 1, 2, 3
New‑onset diabetes in the context of IPMN warrants heightened clinical concern for progression to invasive disease. 2

An elevated CA 19‑9 (> 37 U/mL) should be regarded as a relative indication for surgical resection, especially when accompanied by additional worrisome features (e.g., mural nodules, main‑duct dilation). 1, 3, 6
When CA 19‑9 is elevated, imaging should be promptly reassessed with MRI/MRCP and/or endoscopic ultrasound to determine whether absolute surgical criteria are met. 1
If surgery is not immediately pursued despite an elevated CA 19‑9, the surveillance interval should be shortened to every 3–6 months. 4
Elevated CA 19‑9 must never be used as the sole trigger for surgery; imaging findings must be integrated into the decision‑making process. 1, 3
CA 19‑9 levels can be falsely raised in the setting of jaundice; therefore, the > 37 U/mL cutoff is valid only when biliary obstruction is absent. 1, 3, 6

Patients with normal CA 19‑9 and no other concerning features should continue standard surveillance at 12‑month intervals. 4
Routine glucose monitoring should be maintained to detect the emergence of new‑onset diabetes. 4

Lifelong follow‑up is required after partial pancreatectomy because of the risk of metachronous IPMN lesions. 1, 7
Ongoing CA 19‑9 measurement is recommended as part of the surveillance protocol for the remaining pancreatic tissue. 1