A recent study published in the American Journal of Roentgenology aimed to determine whether a change in the apparent diffusion coefficient (ADC) in prostate cancer seen in MRI can be used to identify growth in tumors.

The United Kingdom-based study, led by researcher Veronica A. Morgan, included 151 men with prostate cancer between the ages of 50 and 83. The study population had an average age of 68 and were undergoing active surveillance that included 3D whole prostate, zonal and tumor volumetric findings documented at endorectal MRI examinations performed twice, with an average break of 21 months.

“Although data are emerging regarding the use of multiple MRI metrics for risk stratification of patients selected for active surveillance, the potential of these images for providing longitudinal tumor volume measurements to monitor growth rate or for quantitative metrics of disease progression remains underexploited,” the researchers wrote.

Tumor ADC was measured on the slice with the largest lesion. Twenty randomly selected patients had the ADC measurements repeated after at least a four-month interval and the limits of agreement of measurements were calculated.

Tumor volume increases greater than the upper limit of agreement was characterized as having measurable growth and their baseline ADCs and change in ADC were compared with tumors that did not have measurable growth.

Results showed:

• 52 (34.4 percent) tumors had measureable growth.
• Baseline ADC and tumor volume were negatively correlated.
• Baseline ADC values did not differ between those without measurable growth, but change in ADC was significantly different.
• Percentage change in tumor volume and percentage change in ADC were negatively correlated.
• A 5.8 percent reduction in ADC indicated a measurable increase in tumor volume with 54.9 percent sensitivity and 77 percent specificity.

“In summary, we found that tumor volume measurements in patients undergoing active surveillance measured with 3D volumetry can vary by 60 percent and that approximately one-fourth of men undergoing active surveillance would have this level of increase at one year,” the authors wrote.