Initial M Staging of Rectal Cancer: FDG PET/MRI with a Hepatocyte-specific Contrast Agent versus Contrast-enhanced CT

Abstract

Background:The performance of PET/MRI in the determination of distant metastases (M stage) in rectal cancer relative to the current practice with contrast material-enhanced CT is largely unknown. Purpose:To compare the staging of clinical M stage rectal cancer with fluorine 18 fluorodeoxyglucose (FDG) PET/MRI (including dedicated liver and rectal MRI) to that of chest and abdominopelvic CT and dedicated rectal MRI. Materials and Methods:From January 2016 to August 2017, patients with newly diagnosed advanced mid to low rectal cancers were recruited for this prospective study (clinicaltrials.gov identifier: NCT0265170). Participants underwent both FDG PET/MRI with dedicated liver and rectal MRI and chest and abdominopelvic CT (the standard-of-care protocol) within 3 weeks of each other. Thereafter, M stage assessment performance was determined by using findings from 6-month clinical follow-up or biopsy as the reference standard. Performance was compared between protocols. Agreement in M stage classification was also assessed. Nonparametric statistical analyses were performed, and P < .05 indicated a significance difference.Results: Seventy-one participants (28 women; mean age 6 standard deviation, 61 years 6 9; age range, 39-79 years) were enrolled. The M stage could not be determined with the standard-of-care protocol in 22 of the 71 participants (31%; 95% confidence interval [CI]: 20.5%, 43.1%) because of indeterminate lesions. However, among these participants, PET/MRI correctly helped identify all 14 (100%; 95% CI: 76.8%, 100%) without metastases and seven of eight (88%; 95% CI: 47.4%, 99.7%) who were later confirmed to have metastases. PET/MRI showed high specificity for ruling out metastatic disease compared with the standard-of-care protocol (98% [54 of 55 participants] vs 72% [40 of 55 participants], respectively; P , .001), without increasing the number of participants with missed metastasis (6% [one of 16 participants] vs 6% [one of 16 participants]; P . .99). Conclusion:PET/MRI with dedicated rectal and liver MRI can facilitate the staging work-up of newly diagnosed advanced rectal cancers by helping assess indeterminate lesions, metastases, and incidental findings better than contrast-enhanced CT, obviating for additional imaging work-up.

18F FDG PET/MRI with hepatocyte-specific contrast agent for M staging of rectal cancer: a primary economic evaluation

“…Furthermore, the high sensitivity and specificity of PET/MRI for determination of the M state in malignant diseases as compared with those of other diagnostics had been proven throughout the last years [8,26]. A study by Queiroz et al showed the high accuracy of PET/MRI in detection of metastatic disease in initial staging of rectal cancer, whereas sensitivity and specificity were even higher in a study by Yoon et al using a hepatocyte-specific contrast agent [6,27].…”

“…Further deterministic sensitivity analysis showed good reliability of the results regarding other input parameters, variation of costs, sensitivity, and specificity of SCI and 18 F FDG PET/MRI, as well as the probability of occurrence of metastases in a wide range still leads to the cost-effectiveness of 18 F FDG PET/MRI over that of SCI. Additionally, the sensitivity and specificity of MRI in this study are based on examinations using a hepatocyte-specific contrast agent, resulting in higher sensitivity for MRI regarding hepatic metastases, which are common in rectal cancer [6]. Fig.…”

“…Sensitivity and specificity values for detection of metastases by 18 F FDG PET/MRI with a hepatocyte-specific contrast agent and SCI were derived from the literature [6].…”

“…Besides adequate diagnosis of local tumor extent, early detection of metastases is important as metastasis-directed therapy regimens including ablation or resection of metastases can be efficient in increasing patient overall survival [3][4][5]. The current diagnostic standard involves magnetic resonance imaging (MRI) of the pelvis and computed tomography (CT) scan of the chest, abdomen, and pelvis, showing relatively high sensitivity but often requiring additional workup for accurate identification and characterization of, e.g., hepatic lesions [6]. In various malignant diseases, positron emission tomography (PET)/MRI provided not only high sensitivity but also high specificity for detection of metastases, avoiding the need for additional diagnostic procedures [7,8].…”

[18F]FDG PET/MRI in rectal cancer

“…Yoon et al [26] studied the diagnostic yield of FDG PET/ MRI for the purpose of M staging in a pool of 71 patients with newly diagnosed advanced mid-to-low rectal cancer. The [18F]FDG PET/MRI examination included additional dedicated MRI sequences of the liver (without and with gadoxetic acid) and the rectum.…”