Radiological evaluation of pancreatic cancer: What is the significance of arterial encasement >180° after neoadjuvant treatment?
P. Mayer, A. Giannakis, M. Klaub, M.M. Gaida, F. Bergmann, H. U. Kauczor, M. Feisst, T. Hackert, M. Loos
European Journal of Radiology Volume 137, 109603, 2021
https://doi.org/10.1016/j.ejrad.2021.109603
Pancreatic ductal adenocarcinoma (PDAC) is a malignant neoplasm with poor prognosis and only 4% 5-years survival due to precocious disease spread beyond pancreatic borders, with encasement of near vessels (1). Currently, the only potentially curative therapy is complete surgical resection. However, less than 30% of patients with newly diagnosed PDAC are eligible for it. In the absence of distant metastases, pancreatic cancer resectability is determined by the degree of tumor vascular infiltration.
Arterial encasement >180° of the celiac axis, the superior mesenteric or the common and proper hepatic arteries makes non-treated PDAC unresectable according to current classifications (2).
Therapeutic planning may be troublesome in patients with PDAC after neoadjuvant therapy (NAT) due to the difficulty in differentiating real arterial infiltration by neoplastic tissue from fibro-inflammatory perivascular alterations in post-therapy CT-scans: an encasement >180° may not correlate with vascular infiltration (3,4).
Mayer and colleagues tried to provide criteria to establish vessels infiltration on CT-scans in Patients with more than 180° arterial encasement after NAT. 70 CT scans were analyzed before and after NAT and the interpretation was then confirmed by surgical and histological examinations.
According to the surgical findings, patient arteries were divided into two groups: 51 non–invaded arteries and 24 invaded arteries.
The CT evaluations and the statistical analyses of the acquired data identified two parameters that held high negative predictive value (NPV) in differentiating invaded and non-invaded arteries after NAT.
The first is an arterial encasement >270°. In this series, this was the most appropriate threshold in differentiating invaded and non-invaded blood vessels after NAT (NPV=89.3%). In fact, only 24 out of 75 analyzed arteries with post-NAT >180° encasement were actually invaded by the tumor.
The second is a solid soft tissue contact with arteries <26 mm: in this case, the arteries are less likely to be infiltrated (NPV=87.5%).
After NAT, non-infiltrating lesions showed a significant decrease in length of solid tissue contact with blood vessels (≥20%), a marked reduction in size (≥20%), and presented significantly lower contiguity scores than infiltrating lesions.
Another interesting result of this study concerns the post NAT levels of Carbohydrate 19.9 antigen (CA 19-9) and of Carcinoembryonic antigen (CEA). In fact, the levels of these serum tumor markers represent another aspect to be taken into consideration in differentiating between non-invaded and invaded arteries, with optimal cut-off values of > 73 U/ml for CA 19-9 and 2,3 mcg/L for CEA.
In conclusion, this article, given that surgical resection is the only cure of PDAC, emphasizes the importance of the defining standardized criteria for a better CT assessment of resectability of PDAC after NAT. Neoadjuvant therapy plays a fundamental role in inducing tumor regression and in converting locally advanced, non-metastatic disease into surgically resectable disease, but after this treatment it is difficult to differentiate viable tumor from fibroinflammatory tissue (5). The major strength of this study is to describe radiological parameters useful in predicting tumor invasion of arteries that present a contiguity by solid soft tissue >180° post NAT. In fact, according to the results of this study, arteries with after NAT encasement >180° and ≤ 70° and with a length of tissue contact <26 mm are unlikely to be invaded. These radiological criteria may have important implications in the treatment of patients with pancreatic cancer because they can contribute to increase chances of surgical approach. However, post NAT discrimination of invaded from non-invaded arteries is still complex and a multidisciplinary assessment is always necessary to optimize treatment planning.
References:
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Martina Borzi is a third-year radiology resident at the Medical Imaging Department of the University of Verona, Italy. In 2017, Dr. Borzi graduated in Medicine and Surgery at the University of Rome Tor Vergata. Her main area of focus is abdominal imaging, especially pancreas and liver imaging. She has been developing particular interest in using software for texture analysis of intrahepatic cholangiocarcinoma.
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