Longitudinal monitoring of apparent diffusion coefficient (ADC) values in patients with multiple myeloma (MM) may classify disease activity in some instances, according to a study published in the European Journal of Radiology.
In this retrospective analysis, researchers assessed whole-body magnetic resonance imaging (MRI) data in patients with stage III MM who were undergoing systemic treatment at the time of analysis. They evaluated bone marrow (BM) involvement using a standardized protocol and measured ADC values in focal lesions (FL) and diffusely involved BM (DIBM) regions. The researchers performed four MRI examinations: the first at baseline (mean, three months), the second at a mean 10 months, the third at a mean 18 months, and the last during a follow-up. Overall, patients were classified into two groups: responders (n=59) and non-responders (n=34).
According to the results, a subgroup of patients with MM undergoing short-term first follow-up experienced a notable increase in ADC in responders (P=0.001) but not non-responders (P=0.9). The researchers observed that ADC levels continually dropped in responders (P=0.02) and increased slightly in non-responders (P=0.8). Moreover, in patients with DIBM, ADC values decreased in responders (P<0.001) and non-responders (P=0.78). The researchers noted that an ADC cutoff value of 0.5-0.6×103 mm2/s for diagnosing inactive disease at follow-up proved unreliable.
“In [patients with MM] with lower tumor burden, the longitudinal course of ADC values is predictable only for FL whereas for DIBM ADC changes considerably overlap between responders and non-responders and are not indicative for assessment of the disease activity,” the researchers concluded.