Diffusion-weighted imaging signal as a predictor of pelvic bone marrow activity in middle-aged and elderly patients with rectal cancer

BackgroundIntensity-modulated radiotherapy targeting areas of active bone marrow effectively reduces hematological toxicity; consequently, it is important to determine whether the bone marrow is active.PurposeTo explore diffusion-weighted imaging (DWI) signal as a potential tool for assessing bone marrow function in middle-aged and elderly patients with rectal cancer.Material and MethodsA retrospective study investigated clinical and magnetic resonance imaging (MRI) data from middle-aged and elderly patients with rectal cancer. Pelvic bone marrow DWI signals (b = 800 s/mm²) were classified as high and iso-low signal groups. Factors influencing the DWI signal were analyzed individually in a multifactorial analysis. Subsequently, a comparison was made of the intravoxel incoherent motion (IVIM) parameters between the high and iso-low signal groups.ResultsThe study involved 73 patients, with 32 in the high-signal and 41 in the iso-low-signal groups. The multifactorial analysis showed that anemia (odds ratio [OR] = 5.264; <i>P</i> = 0.025) and proton density fat fraction (PDFF) (OR = 0.872; <i>P</i> <0.001) were independent factors influencing the DWI signal. In addition, the high-signal group demonstrated significantly lower values of the standard apparent diffusion coefficient (ADC) (median = 0.466 ×10^-3 mm²/s, interquartile range = 0.413-0.550 vs. 0.534 ×10^-3 mm²/s, interquartile range = 0.495-0.594; <i>P</i> <0.01) and the mean diffusion coefficient (D) (0.423 ± 0.065 vs. 0.482 ± 0.090, × 10^-3 mm²/s; <i>P</i> <0.01).ConclusionThe evaluation of pelvic bone marrow function through DWI signals is feasible in middle-aged and elderly patients with rectal cancer. A high DWI signal in the pelvic bone marrow correlates with post-anemic cellular proliferation, indicating active hematopoiesis.