Prognostic Impact of Loss of Spleen Visualization on Whole-Body Diffusion-Weighted Imaging for Multiple Myeloma

Whole–body diffusion–weighted imaging (WB-DWI) is used for evaluating patients with newly diagnosed multiple myeloma (MM), though its prognostic potential is still being developed. As such, Toshiki Terao, MD, and colleagues examined the clinical significant of loss of spleen visualization (LSV) in WB-DWI, and reported that LSV is an indicator for a worse prognosis, even in patients with MM who are responding to treatment.

Their article in Scientific Reports, specified that LSV was associated with a high tumor burden and patients with LSV had a lower spleen–to–spinal cord ratio (SSR). The researchers also observed a negative correlation between SSR and beta-2 microglobulin or bone marrow plasma cell (BMPC), which suggested that “SSR inversely reflected the myeloma burden.”

The team retrospectively reviewed WB-DWI from 96 patients with newly diagnosed MM and 15 patients with smoldering MM. They reported that LSV was seen in 56 patients with newly diagnosed MM and one patient with smoldering MM. Further, patients with newly diagnosed MM and LSV demonstrated higher median infiltration of bone marrow plasma cells and median total diffusion volume than patients without LSV: 80.0% compared to 50.0% (P <0.001) and 540.2 mL compared to 137.0 mL (P = 0.003), respectively. Patients with LSV also had a lower SSR (0.36 versus 0.96, P <0.001) and worse two–year overall survival (84.6% versus 100%, P = 0.032) compared with patients without LSV.

As noted, patients who did not recover spleen visualization during treatment had a worse prognosis, even when they obtained a very good partial response. Finally, spleen histopathological results showed higher cellularity and diffuse myeloma cell infiltration in a patient with LSV and splenic amyloidosis without extramedullary hematopoiesis.

While the authors acknowledged that the study was limited by its retrospective nature, small sample size, and short observation period, they concluded that LSV and a low SSR during pre–treatment WB-DWI are correlated with high tumor volume and poor prognosis. “As patients with LSV during treatment have very poor prognosis despite favorable treatment responses, the relationships between LSV and other variables should be investigated,” the authors added. They called for further research that includes more robust analysis of the spleen to validate their results, and to clarify the function of the spleen in patients with MM.