Lee Haejun, Hwang Kyung-Hoon, Kwon Kwang An
Department of Nuclear Medicine, Gachon University College of Medicine, Gil Medical Center, Incheon 21565, South Korea.
Department of Gastroenterology, Gachon University College of Medicine, Gil Medical Center, Incheon 21565, South Korea.
World J Clin Cases. 2022 Jun 16;10(17):5634-5645. doi: 10.12998/wjcc.v10.i17.5634.
Colon and rectal cancers are among the top five cancers worldwide in terms of their incidence and mortality rates. As the treatment options for cure include surgery even in specific advanced-stage cases, the early detection of lesions is important for applying active treatment methods. Fluorine-18 fluorodeoxyglucose (F-18 FDG) positron emission tomography/computed tomography (PET/CT) is an established imaging study for many types of cancers; however, physiologic uptake in the gastrointestinal tract is a frequent finding and may interfere with lesion identification. Nevertheless, as unexpectedly observed focal colorectal F-18 FDG uptake may harbor malignant lesions, further examination must not be avoided.
To assess the clinical implications of unexpected focal colorectal F-18 FDG uptake by analyzing FDG PET parameters.
A total of 15143 F-18 FDG PET/CT scans performed at our hospital between January 2016 and September 2021 were retrospectively reviewed to identify incidentally observed focal colorectal FDG uptake. Finally, 83 regions showing focal colorectal FDG uptake with final histopathological reports from 80 patients (45 men and 35 women with mean ages of 66.9 ± 10.7 years and 63.7 ± 15.3 years, respectively) were eligible for inclusion in the present study. Each focal hypermetabolic colorectal region was classified as malignant, premalignant, or benign according to the histopathological report. PET parameters such as maximum and peak standardized uptake value (SUVmax and SUVpeak), metabolic tumor volume (MTV), mean SUV of the metabolic tumor volume (mSUVmtv), and total lesion glycolysis (TLG) were measured or calculated for the corresponding hypermetabolic regions. Parametric and non-parametric statistical comparisons of these parameters were performed among the three groups. Receiver operating characteristic curves were plotted to identify cut-off values.
The detection rate of incidental focal colorectal uptake was 0.53% (80/15,143). Of the 83 regions with unexpected focal colorectal hypermetabolism, 28.9% (24/83) were malignant, 32.5% (27/83) were premalignant, and 38.6% (32/83) were benign. Overall, 61.4% of the regions had malignant or premalignant lesions. SUVmax, SUVpeak, and mSUVmtv differentiated malignant and/or premalignant lesions from benign lesions with statistical significance ( < 0.05). mSUVmtv3.5 differentiated malignant from benign lesions, with the largest area under the curve (AUC) of 0.792 and a cut-off of 4.9. SUVmax showed the largest AUC of 0.758 with a cut-off value of 7.5 for distinguishing between premalignant and benign lesions. Overall, SUVmax with a cut-off value of 7.6 (AUC: 0.770, 95% confidence interval (CI): 0.668-0.872; sensitivity, 0.686; specificity, 0.688) was a superior parameter for distinguishing between malignant/premalignant and benign lesions or physiologic uptake. No parameters differentiated malignant from premalignant lesions. Moderate or weak positive correlations were observed between the long diameter of the malignant lesions and PET parameters such as SUVpeak and some mSUVmtv.
Approximately two-thirds (61.4%) of incidental focal hypermetabolic colorectal regions were malignant/premalignant lesions, for which SUVmax was an independent diagnostic parameter. Unexpected suspicious focal colorectal FDG uptake should not be avoided and consideration for further evaluation is strongly recommended not to miss the two-thirds.
就发病率和死亡率而言，结肠癌和直肠癌位列全球五大癌症。由于即使在特定晚期病例中，治愈性治疗方案也包括手术，因此早期发现病变对于应用积极的治疗方法至关重要。氟-18氟脱氧葡萄糖（F-18 FDG）正电子发射断层扫描/计算机断层扫描（PET/CT）是针对多种癌症的一种既定成像检查；然而，胃肠道的生理性摄取是常见现象，可能会干扰病变识别。尽管如此，由于意外观察到的结直肠局灶性F-18 FDG摄取可能隐匿恶性病变，因此绝不能避免进一步检查。
通过分析FDG PET参数评估意外结直肠局灶性F-18 FDG摄取的临床意义。
回顾性分析2016年1月至2021年9月在我院进行的15143例F-18 FDG PET/CT扫描，以识别偶然观察到的结直肠局灶性FDG摄取。最终，83个显示结直肠局灶性FDG摄取且有80例患者（45例男性和35例女性，平均年龄分别为66.9±10.7岁和63.7±15.3岁）最终组织病理学报告的区域符合纳入本研究的条件。根据组织病理学报告，将每个结直肠局灶性高代谢区域分为恶性、癌前或良性。测量或计算相应高代谢区域的PET参数，如最大和峰值标准化摄取值（SUVmax和SUVpeak）、代谢肿瘤体积（MTV）、代谢肿瘤体积的平均SUV（mSUVmtv）和总病变糖酵解（TLG）。对这三组参数进行参数和非参数统计比较。绘制受试者工作特征曲线以确定临界值。
偶然结直肠局灶性摄取的检出率为0.53%（80/15143）。在83个意外结直肠局灶性高代谢区域中，28.9%（24/83）为恶性，32.5%（27/83）为癌前病变，38.6%（32/83）为良性。总体而言，61.4%的区域有恶性或癌前病变。SUVmax、SUVpeak和mSUVmtv在区分恶性和/或癌前病变与良性病变方面具有统计学意义（<0.05）。mSUVmtv 3.5区分恶性与良性病变，曲线下面积（AUC）最大，为0.792，临界值为4.9。SUVmax区分癌前病变与良性病变的AUC最大，为0.758，临界值为7.5。总体而言，临界值为7.6的SUVmax（AUC：0.770，95%置信区间（CI）：0.668 - 0.872；敏感性，0.686；特异性，0.688）是区分恶性/癌前病变与良性病变或生理性摄取的更佳参数。没有参数能区分恶性与癌前病变。在恶性病变的长径与PET参数如SUVpeak和一些mSUVmtv之间观察到中度或弱正相关。
约三分之二（61.4%）的偶然结直肠局灶性高代谢区域为恶性/癌前病变，其中SUVmax是独立的诊断参数。不应避免意外可疑的结直肠局灶性FDG摄取，强烈建议考虑进一步评估，以免遗漏三分之二的病例。
