Branch-duct intraductal papillary mucinous neoplasm (IPMN): Are cyst volumetry and other novel imaging features able to improve malignancy prediction compared to well-established resection criteria?
Raffaella M. Pozzi Mucelli, Carlos Fernández Moro, Marco Del Chiaro, Roberto Valente, Lennart Blomqvist, Nikolaos Papanikolaou, Johannes-Matthias Löhr, Nikolaos Kartalis
Eur Radiol 32, 5144–5155 (2022). doi.org/10.1007/s00330-022-08650-5
Intraductal papillary mucinous neoplasms (IPMN) are epithelial pancreatic cystic tumours of mucin-producing cells that arise from the pancreatic ducts and are usually detected incidentally on cross-sectional imaging. IPMN can be divided into three types according to duct involvement: main duct, branch-duct, and mixed (affecting main and branch ducts) (1). Based on their degree of dysplasia, IPMN range from low-grade dysplasia (LGD) up to high-grade dysplasia and invasive carcinoma (HGD/INV) (1). Current guidelines base their management on several well-established resection criteria (3,4). The cyst size is associated with an increased risk of HGD/INV, but there is not a cut-off size risk established; thus, the size alone is an inappropriate parameter to perform surgery due to its poor predictive positive value for HGD/INV (2).
The aim of this retrospective single-center study was to assess the role of volume, morphology, and other well-established resection criteria in malignancy prediction of patients with branch-duct and mixed-type IPMN.
Patient selection was consecutively done from a prospectively collected database of 345 patients who underwent pancreatic surgery with histologically confirmed IPMN at Karolinska University Hospital from 2008 to 2019.
The inclusion criteria were: a) Preoperative pancreatic MRI with at least one axial and coronal T2W sequence and b) At least one histologically proven BD-IPMN detectable on the T2W images. The exclusion criteria were: a) Main-duct diameter ≥5 mm without a BD-IPMN clearly identifiable at preoperative MRI and b) Solid mass forming pancreatic cancer with or without a main pancreatic duct stricture.
The final study population was 106 patients.
The images of the pancreatic MRI closest to the date of surgery were evaluated by two experienced abdominal radiologists in consensus reading, and one cyst per patient was chosen for the analysis (the largest or the most suspicious for malignancy based on guidelines at the time of surgery). The collected imaging parameters were: maximum cyst diameter on T2WI (axial and coronal), elongation value (a relation between width and length) (5), cyst volume, main pancreatic duct diameter, contrast-enhancing mural nodules, cyst wall thickening (≥2 mm), progress in size during follow-up (≥5 mm/year), solitary/multiple lesions, and cyst location.
Multiple clinical parameters were collected from each patient's electronic record, including: age at surgery, gender, and serum levels of CA 19-9. Also, the grade of dysplasia from each resected IPMN was recorded.
Univariable logistic regression analysis was performed to identify variables associated with HGD/INV. Posteriorly, statistically significant variables were tested with multivariable logistic regression, adjusted for age and gender.
There were no statistically significant differences in cyst volume (OR=1.01, 95% CI: 0.99–1.02 p=0.12) or elongation value (OR=0.38, 95% CI: 0.02–5.93, p=0.49) between patients with LGD and HGD/INV. Also, there was not found an association between HGD/INV and maximum cyst diameter, wall thickness, solitary or multiple lesions, or progress in cyst size (≥5 mm/year). Histological cell subtypes did not correlate with cyst diameter, volume, or elongation value. The results showed that the only variables associated with HGD/INV were also ones that are present in current guidelines (2,3): the presence of contrast-enhancing mural nodules (OR=4.32, 95% CI: 1.18–15.76, p=0.02), the diameter of the main pancreatic duct ≥5 mm (OR=4.2, 95% CI: 1.34–13.1, p=0.01), and elevated serum levels of CA 19-9 (>37 µmol/l) (OR=6.72, 95% CI: 1.89–23.89, p=0.03).
Important limitations of the study were that it was retrospective, the inclusion of only surgically managed IPMN patients (moreover, the indications for surgery varied during the duration of the study), the small patient sample, and the consensual reading of the images by the two radiologists (preventing the assessment of interobserver agreement).
Another important point is that even if the main objective of the study was not demonstrated, the research was published anyway, avoiding publication bias.
In summary, the study shows that neither volumetry nor elongation value can predict malignancy in branch-duct and mixed-type IPMN. And, as known from current guidelines, the dilatation of the main pancreatic duct, contrast-enhancing mural nodules, and elevated serum levels of CA 19-9 are associated with a higher risk of malignancy.
References:
- Ren B, Liu X, Suriawinata AA (2019). Pancreatic ductal adenocarcinoma and its precursor lesions: histopathology, cytopathology, and molecular pathology. Am J Pathol 189:9–21. doi.org 10.1016/j.ajpath.2018.10.004
- Maire F, Couvelard A, Palazzo L, et al. (2013). Pancreatic intraepithelial neoplasia in patients with intraductal papillary mucinous neoplasms. Pancreas 42:1262–1266. doi.org/10.1097/ MPA.0b013e3182962723
- Tanaka M, Fernandez-Del Castillo C, Kamisawa T, et al. (2017). Revisions of international consensus Fukuoka guidelines for the management of IPMN of the pancreas. Pancreatology 17:738– 753. doi.org/10.1016/j.pan.2017.07.007
- The European Study Group on Cystic Tumours of the Pancreas (2018). European evidence-based guidelines on pancreatic cystic neoplasms. Gut 67:789–804. doi.org/10.1136/gutjnl-2018- 316027
- Aghaei Lasboo A, Rezai P, Yaghmai V (2010). Morphological analysis of pancreatic cystic masses. Acad Radiol. doi.org/10. 1016/j.acra.2009.09.013
Eduardo Bättig Arriagada is a fourth-year radiology resident at Hospital Universitari i Politècnic La Fe in Valencia, Spain. His main fields of interest are chest and abdominal imaging, and the use of artificial intelligence in radiology. He has been actively involved in clinical imaging research and has contributed as a co-author in some publications. Besides radiology, his main interests are playing guitar, yoga, and homemade bakery.
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