Kunawudhi Anchisa, Wong Alexandra K, Alkasab Tarik K, Mahmood Umar
Division of Precision Medicine, Athinoula A Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA E-mail :
Asian Pac J Cancer Prev. 2016;17(8):4143-7.
We evaluated all PET/CTs acquired for patients without a primary diagnosis of colorectal cancer, and compared results for those who had subsequent colonoscopy within 6 months, to assess the accuracy of FDG PET/CT for detection of incidental pre-malignant polyps and malignant colon cancers.
Medical records of 9,545 patients who underwent F-18 FDG PET/CT studies over 3.5 years were retrospectively reviewed. Due to pre-existing diagnosis of colorectal cancer, 818 patients were excluded. Of the remainder, 157 patients had colonoscopy within 6 months (79 males; mean age 61). We divided the colon into 4 regions and compared PET/CT results for each region with colonoscopy and histopathologic findings. True positive lesions included colorectal cancer, villous adenoma, tubulovillous adenoma, tubular adenoma and serrated hyperplastic polyp/hyperplastic polyposis.
Of 157 patients, 44 had incidental colonic uptake on PET/CT (28%). Of those, 25 had true positive (TP) uptake, yielding a 48% positive predictive value (PPV); 9% (4/44) were adenocarcinoma. There were 23 false positive (FP) lesions of which 4 were hyperplastic polyps, one was a juvenile polyp and 7 were explained by diverticulitis. Fifty eight patients had false negative PET scans but colonoscopy revealed true pre-malignant and malignant pathology, yielding 23% sensitivity. The specificity, negative predictive value (NPV) and accuracy were 96%, 90% and 87%, respectively. The average SUVmax values of TP, FP and FN lesions were 7.25, 6.11 and 2.76, respectively. There were no significant difference between SUVmax of TP lesions and FP lesions (p>0.95) but significantly higher than in FN lesions (p<0.001). The average size (by histopathology and colonoscopy) of TP lesions was 18.1 mm, statistically different from that of FN lesions which was 5.9 mm (p<0.001). Fifty-one percent of FN lesions were smaller than 5 mm (29/57) and 88% smaller than 10 mm (50/57).
The high positive predictive value of incidental focal colonic FDG uptake of 48% for colonic neoplasia suggests that colonoscopy follow-up is warranted with this finding. We observed a low sensitivity of standardly acquired FDG-PET/CT for detecting small polyps, especially those less than 5 mm. Clinicians and radiologists should be aware of the high PPV of focal colonic uptake reflecting pre-malignant and malignant lesions, and the need for appropriate follow up.
我们评估了所有为未确诊结直肠癌的患者进行的PET/CT检查，并比较了那些在6个月内接受后续结肠镜检查患者的结果，以评估FDG PET/CT检测偶然发现的癌前息肉和恶性结肠癌的准确性。
回顾性分析了9545例在3.5年期间接受F-18 FDG PET/CT检查患者的病历。由于患者已有结直肠癌诊断，818例患者被排除。其余患者中，157例在6个月内接受了结肠镜检查（79例男性；平均年龄61岁）。我们将结肠分为4个区域，并将每个区域的PET/CT结果与结肠镜检查及组织病理学结果进行比较。真阳性病变包括结直肠癌、绒毛状腺瘤、管状绒毛状腺瘤、管状腺瘤和锯齿状增生性息肉/增生性息肉病。
157例患者中，44例在PET/CT上有偶然的结肠摄取（28%）。其中，25例为真阳性摄取，阳性预测值（PPV）为48%；9%（4/44）为腺癌。有23例假阳性（FP）病变，其中4例为增生性息肉，1例为幼年性息肉，7例由憩室炎解释。58例患者PET扫描为假阴性，但结肠镜检查发现了真正的癌前和恶性病变，敏感性为23%。特异性、阴性预测值（NPV）和准确性分别为96%、90%和87%。真阳性、假阳性和假阴性病变的平均SUVmax值分别为7.25、6.11和2.76。真阳性病变和假阳性病变的SUVmax之间无显著差异（p>0.95），但显著高于假阴性病变（p<0.001）。真阳性病变的平均大小（通过组织病理学和结肠镜检查）为18.1mm，与假阴性病变的5.9mm有统计学差异（p<0.001）。51%的假阴性病变小于5mm（29/57），88%小于10mm（50/57）。
偶然发现的局灶性结肠FDG摄取对结肠肿瘤的阳性预测值高达48%，这表明对于这一发现有必要进行结肠镜随访。我们观察到标准采集的FDG-PET/CT检测小息肉的敏感性较低，尤其是那些小于5mm的息肉。临床医生和放射科医生应意识到局灶性结肠摄取反映癌前和恶性病变的高PPV，以及进行适当随访的必要性。
