Evaluation of whole-body diffusion-weighted magnetic resonance imaging for the staging of canine multicentric high-grade lymphoma: a proof-of-concept study

Whole-body diffusion-weighted magnetic resonance imaging (WB-DWI) is a promising modality for lymphoma staging in human medicine, providing functional whole-body imaging without the radiation exposure of PET/CT. WB-DWI has not yet been evaluated for lymphoma staging in dogs, where comprehensive staging currently relies on multiple imaging modalities and organ cytology. This pilot study evaluated the performance of WB-DWI for staging canine multicentric lymphoma by comparing its findings to conventional staging methods at diagnosis and following induction chemotherapy. Five dogs with multicentric high-grade lymphoma underwent conventional staging (physical examination, complete blood count, blood smear, biochemistry panel, thoracic radiographs, abdominal ultrasound, and cytology of the liver, spleen, and bone marrow) alongside WB-DWI. Staging was performed at diagnosis and following one month of induction chemotherapy with L-COP or L-CHOP. WB-DWI findings were compared with conventional methods to evaluate its accuracy in determining disease extent and monitoring treatment response, using Cohen’s Kappa coefficient to evaluate agreement. Conventional staging methods classified three dogs as stage IV and two as stage V (bone marrow infiltration). WB-DWI staging was concordant in three of five cases, classifying one as stage III, three as stage IV, and one as stage V, with an overall agreement of 72% across all anatomical sites. Cohen’s Kappa agreement score indicated moderate agreement for lymph nodes (κ = 0.531) and bone marrow (κ = 0.545), but only slight agreement for the liver and spleen (κ = 0.0). Following induction chemotherapy, all dogs achieved complete remission based on conventional staging. WB-DWI confirmed the resolution of lymph node and bone marrow disease in all dogs. This pilot study demonstrates the feasibility of WB-DWI as a non-invasive, single examination for the staging and monitoring of canine multicentric high-grade lymphoma. However, additional work is necessary to improve its sensitivity, particularly for detecting liver infiltration, and larger studies are warranted to validate these preliminary findings.