Whole-body diffusion-weighted imaging with apparent diffusion coefficient mapping for treatment response assessment in patients with diffuse large B-cell lymphoma: Pilot study

The aim of this pilot study was to assess post-treatment apparent diffusion coefficient (ADC) changes of diffuse large B-cell lymphoma lesions on respiratory-gated whole-body diffusion-weighted imaging (DWI), with integrated ¹⁸F-fluoro-2-deoxyglucose positron emission tomography/ computed tomography (PET/CT) as the reference standard. Materials and Methods: A total of 15 patients underwent both whole-body DWI (b = 50, 400, 800 s/mm²) and PET/CT before initiation and after 4 cycles of chemotherapy. ADC of residual masses (lymph node and organ lesions) was assessed both visually and quantitatively, including measurement of mean ADC (ADC). Results: After chemotherapy, among 85 examined lymph node regions, residual nodes were present in 62 (73%) regions on DWI. Of these 62 regions, 26 had persistent lymph nodes with longest transverse diameter >10 mm, ie, positive based on DWI size criteria. The mean ADC of these 26 regions increased from 0.658 >10 ^-3 ± 0.153 mm²/s (standard deviation) at baseline to 1.501 × 10^-3 ± 0.307 mm²/s (paired t test, P < 0.0001). Only 6 of these 26 regions were considered positive on PET/CT. Combining visual ADC analysis to size criteria reduced the number of false-positive results of DWI from 20 to 2 regions. For organ involvement, ADC values also increased compared with baseline (1.558 × 10^-3 ± 0.424 mm²/s vs. 0.675 × 10^-3 ± 0.135 mm²/s, respectively; P = 0.0009). Conclusions: Whole-body DWI with ADC mapping can show a significant increase in ADC values of residual masses persisting after treatment and may help to assess the treatment response in patients with diffuse large B-cell lymphoma.