A retrospective preliminary study of intrapancreatic late enhancement as a noteworthy imaging finding in the early stages of pancreatic adenocarcinoma
Yoshihiro Konno, Yasuhiro Sugai, Masafumi Kanoto, Keisuke Suzuki, Toshitada Hiraka, Yuki Toyoguchi & Kazuho Niino
European Radiology 33, 5131–5141 (2023). doi.org/10.1007/s00330-022-09388-w
Pancreatic adenocarcinoma (PAC) represents the most common primary pancreatic malignancy (90%) [1]. Accounting for 2% of all cancer cases, it has the lowest 5-year survival rate of all solid cancers (5-9%) and is the fourth-leading cause of cancer-related death in USA and Canada [1,2]. Due to its aggressive behavior, early diagnosis is critical for appropriate management. Imaging has a central role in this regard as early PAC is often challenging to diagnose clinically [2].
CT and MRI are the cornerstones of PAC detection, staging, treatment response assessment and recurrence diagnosis, with CT often being the test of choice due to its reproducibility and availability [1,3]. The primary imaging finding is a hypo-attenuating/intense pancreatic mass on contrast-enhanced studies [4]. However, up to 27% of tumors <2 cm in size can be isoattenuating at CT [4]. Indirect findings (IFs) include main pancreatic duct abnormalities (MPDA) with dilatation (when associated with common bile duct dilatation = “double duct”
sign), contour distortion, focal pancreatic parenchymal atrophy (FPPA), vascular encasement and loss of pancreatic lobulation [3,4]. The most common focal pancreatic abnormalities noted in pre-diagnostic CT (at least 1 year before the diagnosis of PAC) were FPPA, focal faint parenchymal enhancement and focal MPDA [5].
The aim of this retrospective study was to analyze intrapancreatic late enhancement (ILE) in pre-diagnostic CT studies of patients with pathologically confirmed PAC and its potential significance as an early indirect finding in PAC. The final study population enrolled 32 patients (23 men and 9 women, median age 72 years), with pathologically confirmed PAC (surgically or by biopsy). The main inclusion criterion was a contrast-enhanced CT (CECT) study performed 6 months to 5 years prior to the pathological diagnosis of PAC, without a visible focal pancreatic mass. Exclusion criteria included patients with (a) previous pancreatectomy, (b) difficult distinction from inflammatory changes and (c) carcinoma in situ.
Technically, all CECT exams were obtained using a helical CT (64-320 rows) with 1 or 5 mm thick slices, with either monophasic (late phase 120s after contrast injection) or multiphasic (early and late arterial, portal and late phase at 180s after contrast injection) protocols. ILE was defined as a focal enhancement in the pancreatic parenchyma of any size or shape, with subsequent quantitative evaluation in Hounsfield Units (HU) by calculating the ILE-to-pancreas contrast (HU [region of ILE] – HU [pancreatic parenchyma]). Other IFs were also defined in the study, including FPPA and MPDA, as well as cystic lesions. To verify the potential significance of ILE, two independent experienced radiologists, blind to all clinical data, reviewed representative pre-diagnostic CT images and indicated potential sites where PAC would become apparent in the future. The evaluation was done both before and after the two observers received lectures on the significance of ILE as an IF in PAC, with subsequent comparison between the two assessments in terms of lesion detection and interobserver agreement.
The positive group (with present IFs) included 23 cases (72%), without any significant differences in terms of demographics, preexisting conditions or time interval to diagnosis compared to the negative group (without IFs). Incidental PAC (clinically asymptomatic) was significantly more frequent in the positive group with a tendency for more frequent body/tail lesions, while in the negative group tumor size tended to be larger at diagnosis.
In the positive group, ILE was observed in 14 patients (63%) either alone (35%) or in combination with other IFs like FPPA and MPDA (26%), with a higher proportion of pancreatic head lesions in those with ILE alone. Median long-axis diameter of ILE was 10 (IQR 5-11) mm with a median ILE-to-pancreas contrast value of 24 (IQR 17-33) HU. Interobserver agreement and lesion detection improved after ILE awareness.
Limitations of the study acknowledged by the authors include single-center small sample size, possible overestimation of IFs and ILE and unknown extent of false positives, issues that could be clarified in large-scale multicenter studies.
In conclusion, this study emphasizes the role of ILE as an important imaging feature in the early diagnosis of PAC, either as a standalone finding or associated with other IFs. Lesion detection could be improved by including a late phase (at least 120s after injection) in the CECT study and by training radiologists to be familiar with ILE significance.
References:
1. Morani AC, Hanafy AK, Ramani NS et al. Hereditary and Sporadic Pancreatic Ductal Adenocarcinoma: Current Update on Genetics and Imaging. Radiology: Imaging Cancer, 2(2),e190020 (2020). doi:10.1148/rycan.2020190020
2. LeBlanc M, Kang J, Costa AF. Can we rely on contrast-enhanced CT to identify pancreatic ductal adenocarcinoma? A population-based study in sensitivity and factors associated with false negatives. European Radiology (2023). doi:10.1007/s00330-023-09758-y
3. Haj-Mirzaian A, Kawamoto S, Zaheer A et al. Pitfalls in the MDCT of pancreatic cancer: strategies for minimizing errors. Abdominal Radiology 45, 457–478 (2020). doi:10.1007/s00261-019-02390-9
4. Schima W, Adam EJ, Morgan RA. The Pancreas. In: Adam A, Dixon AK, Gillard JH, Schaefer-Prokop CM, eds. Grainger & Allison’s Diagnostic Radiology. 6th ed. Churchill Livingstone – Elsevier Limited; 2015:803-831.
5. Toshima F, Watanabe R, Inoue D et al. CT Abnormalities of the Pancreas Associated With the Subsequent Diagnosis of Clinical Stage I Pancreatic Ductal Adenocarcinoma More Than 1 Year Later: A Case-Control Study. American Journal of Roentgenology 217, 6, 1353-1364 (2021). doi:10.2214/AJR.21.26014
Andrei Mavroian is a fourth-year radiology resident at Cluj-Napoca County Emergency Hospital. He completed his undergraduate medical degree at “Gr. T. Popa” University of Medicine and Pharmacy in 2019. His field of interest includes neuroradiology, cardiovascular imaging and artificial intelligence, with a focus on abdominal imaging.
Comments may be sent to: andrei.mavroian11(at)gmail.com
