Diagnostic Value of Whole Body Diffusion Weighted Imaging for Screening Primary Tumors of Patients with Metastases

Added value of body MRI to detect primary abdominal malignancies in the diagnostic work-up of patients with adenocarcinoma of unknown primary

PURPOSE

This study aimed to evaluate the added benefit of body MRI (covering the chest, abdomen, and pelvis) to detect the primary tumour in patients with adenocarcinoma of unknown primary (ACUP) and a suspected abdominal malignancy in whom previous diagnostic work-up with CT and/or FDG-PET/CT did not yield a primary tumour diagnosis.

METHODS

Thirty ACUP patients with a suspected primary tumour in the abdomen/pelvis (based on pathology and/or pattern of disease) underwent MRI (T2-weighted, DWI, pre- and post-contrast T1-weighted) after completion of their initial diagnostic work-up with CT and/or PET/CT. Effects of MRI to establish a primary tumour diagnosis (and to detect additional metastatic sites) were documented. Integration of all available imaging data, additional diagnostic procedures (e.g., endoscopy), histopathology, and whole genome sequencing served as the composite standard of reference.

RESULTS

MRI rendered a possible primary tumour diagnosis in 16/30 (53%) cases, which aligned with the final clinical diagnosis in 9/16 (56%) of these cases, thus resulting in a confirmed primary tumour diagnosis in 30% of our total patient cohort. These included four gastrointestinal, two hepatobiliary, one pancreatic, one ovarian and one breast cancer. MRI revealed extra metastatic sites in five patients (17%).

CONCLUSION

MRI can be of added value in the diagnostic work-up of ACUP patients with a suspected primary tumour originating from the abdomen or pelvis, in particular to detect gastrointestinal or hepatobiliary malignancies. Larger studies are needed to confirm these results and identify specific ACUP patients that are most likely to benefit from MRI.

KEY POINTS

Question Can body MRI help identify the primary tumour in patients with adenocarcinoma of unknown primary (ACUP)? Findings In this pilot of n = 30 ACUP patients with clinically suspected abdominal malignancies, body MRI was able to establish the primary tumour in 30% of cases. Clinical relevance Body MRI can be of added value (as an adjunct to CT and/or PET/CT) in the diagnostic work-up of ACUP patients with a suspected primary tumour originating from the abdomen or pelvis, especially to detect gastrointestinal or hepatobiliary malignancies.

Diagnostic value of whole-body diffusion-weighted magnetic resonance imaging for detection of primary and metastatic malignancies: a meta-analysis

PURPOSE

To perform a meta-analysis to evaluate the diagnostic performance of whole-body diffusion-weighted magnetic resonance imaging (WB-DWI) technique in detection of primary and metastatic malignancies compared with that of whole-body positron emission tomography/computed tomography (WB-PET/CT).

MATERIALS AND METHODS

Search Pubmed, MEDLINE, EMBASE and Cochrane Library database from January 1984 to July 2013 for studies comparing WB-DWI with WB-PET/CT for detection of primary and metastatic malignancies. Methodological quality was assessed by the quality assessment of diagnostic studies (QUADAS) instrument. Sensitivities, specificities, predictive values, diagnostic odds ratio (DOR) and areas under the summary receiver operator characteristic curve (AUC) were calculated. Potential threshold effect, heterogeneity and publication bias were investigated.

RESULT

Thirteen eligible studies were included, with a total of 1067 patients. There was no significant threshold effect. WB-DWI had a similar AUC (0.966 (95% CI, 0.940-0.992) versus 0.984 (95% CI, 0.965-0.999)) with WB-PET/CT. No significant difference was detected between AUC of WB-DWI and WB-PET/CT. WB-DWI had a pooled sensitivity of 0.897 (95% CI, 0.876-0.916) and a pooled specificity of 0.954 (95% CI, 0.944-0.962). WB-PET/CT had a pooled sensitivity of 0.895 (95% CI, 0.865-0.920) and a pooled specificity of 0.975 (95% CI, 0.966-0.981). Heterogeneity was found to stem primarily from data type (per lesion versus per patient), MR sequence (DWIBS only and DWIBS with other sequence), and primary lesion type (single type and multiple type). The Deeks's funnel plots suggested the absence of publication bias.

CONCLUSION

WB-DWI has similar, good diagnostic performance for the detection of primary and metastatic malignancies compared with WB-PET/CT. DWIBS with other MR sequences could further improve the diagnostic performance. More high-quality studies regarding comparison of WB-DWI and WB-PET/CT and combination of them in detecting malignancies are still needed to be conducted.

Competing Technology for PET/Computed Tomography: Diffusion-weighted Magnetic Resonance Imaging

Whole-body diffusion-weighted (DW) imaging is a recent development. The image contrast is based on differences in mobility of water between tissues and reflects tissue cellularity and integrity of cell membranes. The tissue water diffusivity is quantified by the apparent diffusion coefficient. By performing imaging at multiple imaging stations, whole-body DW imaging has been applied to improve tumor staging, disease characterization, as well as for the assessment of treatment response. Information from DW imaging studies could be combined with those using PET imaging tracers to further refine and improve the assessment of patients with cancer.

Cancer of unknown primary sites: what radiologists need to know and what oncologists want to know

OBJECTIVE

In this article, we review the role of imaging in cancer of unknown primary site (CUP) diagnosis and management and the utility of immunohistochemistry, serum tumor markers, and molecular profiling in the optimized care of CUP patients.

CONCLUSION

With advances in imaging, pathology, and molecular medicine, the diagnosis and management of CUP have evolved into more personalized and site-specific therapies. A multidisciplinary integrated approach among oncologists, pathologists, and radiologists is extremely important.

PET and PET/CT for unknown primary tumors

Carcinoma of unknown primary (CUP) is defined as histologically proven metastatic disease that, after a complete diagnostic work-up, yields no primary detectable tumor. CUP is one of the ten most frequent cancers, with overall poor outcome. Detection of the unknown primary tumor is of crucial importance in this scenario, since it might help to select and offer definitive treatment, which, in turn, may improve patient prognosis. Additional diagnostic work-up, usually consisting of a combination of several radiological and endoscopic investigations and serum tumor marker studies, can be time consuming, expensive, and pose a significant burden to the patient. The final diagnostic yield of these tests is often limited. Combined positron emission tomography/computed tomography (PET/CT), using the radiotracer (18)F-fluoro-2-deoxyglucose (FDG), may be of great value in the management of patients with CUP for the detection of primary tumors. This chapter gives a brief introduction to the syndrome of CUP, followed by an outline of the rationale, use, and utility of FDG-PET/CT in CUP, and concludes with a discussion on the challenges and future directions in the diagnostic management of patients with CUP.

FDG PET/CT in carcinoma of unknown primary

Carcinoma of unknown primary (CUP) is a heterogeneous group of metastatic malignancies in which a primary tumor could not be detected despite thorough diagnostic evaluation. Because of its high sensitivity for the detection of lesions, combined ¹⁸F-fluoro-2-deoxyglucose positron emission tomography (FDG PET)/computed tomography (CT) may be an excellent alternative to CT alone and conventional magnetic resonance imaging in detecting the unknown primary tumor. This article will review the use, diagnostic performance, and utility of FDG PET/CT in CUP and will discuss challenges and future considerations in the diagnostic management of CUP.