Can Diffusion-Weighted MRI Have an Impact in Detecting Recurrent Pancreatic Cancer?

New research suggests that diffusion-weighted magnetic resonance imaging (MRI) may be beneficial in differentiating between local tumor recurrence and post-op fibrosis after resection of pancreatic ductal adenocarcinoma (PDAC).

In a recently published retrospective study in the American Journal of Roentgenology (AJR), researchers looked at 66 patients (mean age of 60.5 years) who had PDAC resection and post-op computed tomography (CT) that showed a soft tissue lesion. Comparing the subsequent use of diffusion-weighted MRI and conventional MRI to differentiate between local tumor recurrence and post-op fibrosis, researchers found higher sensitivity with diffusion-weighted MRI.

For two independent observers, researchers noted sensitivity rate increases of 27 percent and 42.3 percent with the combination of MRI and diffusion-weighted imaging (DWI) in comparison to MRI alone. The study authors also noted a greater than threefold increase in subjective diffusion restriction for local tumor recurrence in comparison to post-op fibrosis (88.5 percent versus 25 percent). This difference is likely due to the compact tumor cellularity of recurrent tumors, according to the researchers.

The combination of DWI and MRI also resulted in a higher area under the curve (AUC) in comparison to conventional MRI in diagnosing local tumor recurrence for both observers (.805 versus .707 for observer one; .898 versus .637 for observer two), according to the study.

“The findings support the utility of DWI when performing and interpreting MRI to evaluate suspected local recurrence after PDAC resection,” wrote Tae Wook Kang, MD, who is affiliated with the Department of Radiology and the Center for Imaging Science at the Samsung Medical Center at the Sungkyunkwan University School of Medicine in Seoul, Korea, and colleagues.

The study authors acknowledged the lack of a statistically significant increase in specificity with DWI and MRI. However, they did note higher interobserver agreement with the combination. Additionally, Kang and colleagues found that the median apparent diffusion coefficient (ADC) was lower for local tumor recurrence (1.3 x10-3 mm²/s) in comparison to post-op fibrosis (1.7 x 10-3 mm²/s).

While recognizing the need for future prospective studies to further assess the effectiveness of DWI for post-PDAC monitoring, the study authors said there is potential for more timely recognition of tumor recurrence.

“MRI with DWI as a problem-solving tool during post-operative surveillance after PDAC resection could facilitate earlier detection of recurrences, guiding prognostic assessment and treatment decisions,” noted Kang and colleagues.

In regard to study limitations, the authors acknowledged the small sample size and the possibility of patient selection bias due to the retrospective design. The researchers used 3-T MRI and a hepatobiliary contrast agent but noted that the use of 1.5-T MRI or an extracellular contrast agent may have lead to different results.