Emerging non-invasive imaging biomarkers of Ki-67 in pancreatic cancer: Toward predictive precision oncology

Table 1 Advantages and limitations of modalities used in the diagnosis of pancreatic cancer

Methods	Advantages	Limitations	Clinical utility for Ki-67 estimation	Utility in Ki-67 prediction	Validation status
US	Easy to use, flexible and intuitive, non-invasive and radiation-free	Difficulty visualizing the entire pancreas	No validated biomarkers	Low	Research-only
CT	Excellent spatial and temporal clarity	Inability to diagnose pancreatic lesions accurately	Texture analysis (low entropy excludes high Ki-67 expression)[67]	Moderate	Transitional
MRI	Exceptional imaging for depicting local pancreatic disease	Expensive and less widely available	Diffusion restriction (low ADC) predicts high Ki-67 expression for preoperative risk stratification[48,49]	High	Limited clinical use
PET	Advantages are obvious when detecting extrapancreatic metastasis and evaluating the tumor load throughout the body	Expensive, less widely available and contrast exposure	Focal hypermetabolism (high SUV) triggers targeted biopsy for suspected aggressive lesions[58]	Moderate	Routine clinical
CEUS	The major blood vessels and microvascular system within the pancreas can be displayed	Highly subjective and its accuracy is highly influenced by the operator’s skill level and experience	Elevated perfusion kinetics (high Rs1090) may reduce reliance on biopsy in high-bleeding-risk patients	High	Research-only

Research-only: Preliminary evidence, requires technical optimization. Transitional: Retrospective validation, prospective trials ongoing. Limited clinical: Single-center prospective validation, pending multi-center confirmation. Routine clinical: Prospective multi-center validation, incorporated into major guidelines. US: Ultrasound; CT: Computed tomography; MRI: Magnetic resonance imaging; PET: Positron emission tomography; CEUS: Contrast-enhanced ultrasound; ADC: Apparent diffusion coefficient; SUV: Standard uptake value; Rs1090: Rise slope 10%-90%.