Baseline Tumor Burden is Associated with Bone Marrow Involvement in Low-grade

Abstract Background Bone marrow biopsy (BMB) is a cornerstone in the staging of aggressive lymphomas, yet its relevance in indolent lymphomas remains under scrutiny. This study assessed the utility of BMB in positron emission tomography/computed tomography (PET/CT) staging for low-grade follicular lymphomas (FL). Methods This retrospective study analyzed the records of patients newly diagnosed with low-grade (grade 1–2) FL who underwent initial staging with both PET/CT and BMB at two Chinese institutions from 2010 to 2022. Data for a cohort of 171 patients were analyzed, 27 had positive BMB results. Results Using BMB as the benchmark for diagnostic accuracy, PET/CT demonstrated an overall accuracy of 86.5% in detecting BM involvement. BMB led to the reclassification of 13 patients to stage IV disease who were initially evaluated as stage III via PET/CT. In patients with advanced-stage disease, positive BMB results correlated with extramedullary tumor burden. Patients were stratified as low-, intermediate-, and high-risk using four independent BMB-positive risk factors: sex, Eastern Cooperative Oncology Group performance score > 1, elevated beta2 micro-globulin levels, and involvement of more than four lymph node regions. The BMB-positive rates for the risk categories were 5.6%, 40.7%, and 68.8%, respectively. Over a median follow-up period of 34 months, there was no observed survival difference between BMB-positive and BMB-negative patients. Conclusions Baseline PET/CT can safely and effectively substitute for BMB in the staging of early-stage, low-grade FL. However, in patients with advanced-stage disease, routine BMB provides additional diagnostic value over PET/CT. The rate of BMB positivity is strongly linked to tumor burden.