In recent years, the application of positron emission tomography/computed tomography (PET/CT) in oncology has transformed diagnostic protocols, particularly with the use of fluorine-18 fluorodeoxyglucose (^18F-FDG). This radiotracer highlights metabolic activity in tissues, offering unparalleled insight into tumor biology. A groundbreaking study published in BMC Cancer now sheds light on the enhanced diagnostic potential of dual-time-point ^18F-FDG PET/CT imaging for colorectal carcinoma and advanced adenoma, conditions often indicated by fixed focal FDG uptake in colorectal regions.
Colorectal cancer (CRC) remains one of the leading causes of cancer-related morbidity and mortality worldwide. Early and accurate detection is vital for improving patient outcomes. However, interpreting fixed focal ^18F-FDG uptake in the colorectal area on PET/CT scans presents diagnostic challenges as these findings can represent a spectrum from benign lesions to malignancy. This ambiguity often leads to unnecessary invasive procedures or delayed treatment. The recent study aims to clarify this diagnostic gray zone by evaluating the efficacy of dual-time-point scanning—a technique where imaging is performed at two distinct time intervals following tracer injection.
The retrospective nature of the research involved 122 patients scanned between January 2019 and December 2023, with a collective assessment of 141 colorectal lesions exhibiting fixed focal FDG uptake. Inclusion criteria mandated colonoscopic evaluation within one month post-PET/CT to ensure histopathological correlation, crucial for diagnostic accuracy. Advanced adenomas, important precursors to CRC, were stringently defined based on size (>10 mm), histological architecture (presence of villous components), and cytological features such as high-grade dysplasia.
Methodologically, the study employed quantitative measures derived from PET/CT images, namely the maximum standardized uptake value (SUVmax) and the retention index (RI). SUVmax quantifies the highest radiotracer uptake within a lesion, reflecting metabolic intensity, while RI evaluates changes in SUVmax between early and delayed scans—offering insights into dynamic tracer retention that may distinguish malignant from benign processes.
Statistical analysis revealed compelling evidence: colorectal carcinomas and advanced adenomas demonstrated significantly elevated SUVmax in delayed PET/CT scans compared to non-advanced lesions (mean 25.1 ± 14.2 vs. 14.5 ± 7.5). Furthermore, the retention index was markedly higher in malignant or pre-malignant lesions, underscoring metabolic persistence or accumulation over time. These findings suggest that dual-time-point imaging enriches diagnostic specificity by leveraging temporal metabolic patterns rather than static snapshots.
Notably, multi-variable logistic regression established delayed SUVmax and RI as independent predictors of colorectal carcinoma/advanced adenoma. The odds ratios indicated that even incremental increases in these metrics substantially raised the likelihood of malignancy, emphasizing their clinical relevance. Integrating both parameters achieved an area under the receiver operating characteristic curve (AUC) of 0.801, signifying excellent discriminatory power.
Beyond statistical metrics, the study proposed a risk stratification model based on threshold levels of delayed SUVmax and RI. This classification delineated patients into low-, moderate-, and high-risk subgroups, with corresponding predictive probabilities of advanced lesions. Such stratification holds immense promise for personalized patient management, potentially guiding decisions regarding invasive diagnostic procedures or surveillance intensity.
These findings have far-reaching implications beyond colorectal oncology. The concept of dual-time-point PET/CT imaging may be extrapolated to other anatomical sites and cancer types where FDG uptake patterns blur lines between benignity and pathology. This bidirectional imaging approach pioneers a nuanced understanding of tumor metabolism over time, challenging conventional single-scan paradigms.
Despite its strengths, the study also encountered inherent limitations common to retrospective analyses—including selection biases and the need for larger, multicentric prospective validation. Future research should aim to standardize scanning protocols, explore molecular correlates of FDG retention kinetics, and evaluate cost-effectiveness in clinical algorithms.
Clinicians and radiologists stand to benefit greatly from incorporating dual-time-point imaging metrics into routine colorectal cancer diagnostics. This technique could reduce false positives, minimize unnecessary procedures, and prompt timely interventions for advanced neoplasms. Moreover, patient outcomes might improve through tailored surveillance strategies grounded in objective metabolic data rather than morphological suspicion alone.
From a technical perspective, the dual-time-point approach introduces complexities related to scanner timing, post-processing, and patient compliance. Optimizing these factors is essential for reproducibility and widespread adoption. Advanced software algorithms and artificial intelligence integration could further enhance image analysis, extracting subtle metabolic features invisible to the human eye.
The broader scientific community anticipates that this method may synergize with emerging biomarkers and molecular imaging probes, enriching the multi-modal diagnostic landscape. For colorectal cancer, a disease with heterogeneous behavior and progression patterns, such innovation is particularly vital.
In conclusion, this seminal investigation underscores the pivotal role of delayed ^18F-FDG PET/CT and retention index evaluation in identifying colorectal carcinoma and advanced adenoma among patients exhibiting fixed focal colorectal FDG uptake. By providing robust quantitative predictors and demonstrating improved diagnostic accuracy, dual-time-point imaging heralds a new era in precision oncology diagnostics. As this paradigm gains traction, it promises to revolutionize patient pathways and improve colorectal cancer detection rates worldwide.
Subject of Research: Dual-time-point ^18F-FDG PET/CT imaging in the diagnosis of colorectal carcinoma and advanced adenoma in patients with fixed focal colorectal ^18F-FDG uptake.
Article Title: Dual-Time-Point ^18F-FDG PET/CT imaging in the diagnosis of colorectal carcinoma or advanced adenoma in patients with fixed focal colorectal ^18F-FDG uptake.
Article References:
Meng, B., Ma, Y., Wang, Y. et al. Dual-Time-Point ^18F-FDG PET/CT imaging in the diagnosis of colorectal carcinoma or advanced adenoma in patients with fixed focal colorectal ^18F-FDG uptake. BMC Cancer 25, 755 (2025). https://doi.org/10.1186/s12885-025-14129-5
Image Credits: Scienmag.com
