Patients with diffuse large B-cell lymphoma (DLBCL) and pre-treatment bone marrow (BM) involvement require a restaging BM biopsy to document complete remission (CR). We investigated whether BM assessment by restaging PET-CT could obviate the need for a repeat BM biopsy. Patients with DLBCL and a positive BM biopsy at diagnosis were identified from the Mayo Clinic Lymphoma Data Base. The concordance of BM status on restaging histopathology and PET-CT reports and the positive (PPV) and negative predictive value (NPV) of PET-CT were determined. One thousand eighty patients with DLBCL were evaluated and 69 patients (6%) had DLBCL involving the BM at diagnosis. Of 46 patients who completed frontline chemoimmunotherapy, 34 had a restaging PET-CT and BM biopsy and were included in the analysis. Thirty-three patients had a negative BM by both PET-CT and BM biopsy; one patient had persistent BM involvement by biopsy and PET-CT. Thus, restaging PET-CT had 100% PPV and 100% NPV for assessing residual BM disease. The findings were validated in a prospective cohort of 68 DLBCL patients treated on a phase II clinical trial where four patients (6%) had DLBCL involving the BM at diagnosis. All had a negative BM by both restaging BM biopsy and PET-CT. Compared with the gold standard of BM biopsy, PET-CT had a 100% NPV to exclude residual BM disease after frontline therapy. If further validated, DLBCL practice guidelines and response criteria could be modified so that BM biopsy is no longer required to document CR if the restaging PET-CT is negative.
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