Comparison of DWI and PET/CT in evaluation of lymph node metastasis in uterine cancer

Abstract

Aim: To investigate diffusion-weighted imaging (DWI) and positron emission tomography and computed tomography (PET/CT) with IV contrast for the preoperative evaluation of pelvic lymph node (LN) metastasis in uterine cancer.

Methods: Twenty-five patients with endometrial or cervical cancer who underwent both DWI and PET/CT before pelvic lymphadenectomy were included in this study. For area specific analysis, LNs were divided into eight regions: both common iliac, external iliac, internal iliac areas, and obturator areas. The classification for malignancy on DWI was a focally abnormal signal intensity in a location that corresponded to the LN chains on the T1WI and T2WI. The criterion for malignancy on PET/CT images was increased tracer uptake by the LN.

Results: A total of 36 pathologically positive LN areas were found in 9 patients. With DWI, the sensitivity, specificity, positive predictive value, negative predictive value and accuracy for detecting metastatic LNs on an LN area-by-area analysis were 83.3%, 51.2%, 27.3%, 93.3% and 57.0%, respectively, while the corresponding values for PET/CT were 38.9%, 96.3%, 70.0%, 87.8% and 86.0%. Differences in sensitivity, specificity and accuracy were significant (P < 0.0005).

Conclusion: DWI showed higher sensitivity and lower specificity than PET/CT. Neither DWI nor PET/CT were sufficiently accurate to replace lymphadenectomy.

Keywords: Diffusion-weighed imaging; Lymph node metastasis; Magnetic resonance imaging; Positron emission tomography and computed tomography; Uterine cancer.

Figure 1

A 61-year-old woman with endometrial cancer with lymph node metastases in left internal iliac area. A: T2-weighted magnetic resonance imaging shows a small lymph node (LN) in left internal iliac area (arrow); B: The LN seen in (A) shows moderately abnormal signal intensity on diffusion-weighted imaging (DWI) (arrow) suggesting presence of nodal cancer spread; C: Enhanced CT component of positron emission tomography and computed tomography (PET/CT) shows a small LN in left internal iliac area (arrow); D: PET/CT shows that abnormal ¹⁸F-fluorodeoxyglucose uptake corresponds to the LN seen in (C) (arrow), suggesting the presence of nodal cancer spread. Histopathological specimen findings confirmed extensive LN involvement by cancer in the node. Both DWI and PET/CT were true-positive for the node.

Figure 2

A 51-year-old woman with cervical cancer with lymph node metastases in left internal iliac area. A: T2-weighted magnetic resonance imaging shows two small lymph nodes (LNs) in right and left internal iliac areas (arrows); B: These two LNs seen in (A) show moderately abnormal signal intensity on diffusion-weighted imaging (DWI) (arrows), suggesting the presence of nodal cancer spread; C: Enhanced computed tomography (CT) component of positron emission tomography and CT (PET/CT) shows two small LNs in right and left internal iliac areas (arrows); D: PET/CT shows no ¹⁸F-fluorodeoxyglucose uptake corresponding to the two LNs seen in (C) (arrows) suggesting the absence of nodal cancer spread. Histopathological specimen findings confirmed extensive LN involvement by cancer in left internal iliac LN and no involvement in right internal iliac LN. DWI was false-positive for the right and true-positive for the left node. PET/CT was true-negative for the right and false-negative for the left node.