Assessing bone marrow involvement in persons with a new diagnosis of diffuse large B-cell lymphoma (DLBCL) is better accomplished with 18F-FDG positron emission tomography/computed tomography (PET/CT) than with bone marrow biopsy, contend the authors of a recent study.

DLBCL is the most frequent subtype of high-grade non-Hodgkin lymphoma. The sensitivity of bone marrow biopsy for the detection of bone marrow involvement in new cases of DLBCL can be low because of sampling error if the bone marrow involvement is focal rather than diffuse, explained a team led by Louis Berthet in the Society of Nuclear Medicine’s The Journal of Nuclear Medicine (2013;54[8]:1244-1250). For initial staging of DLBCL, 18F-FDG PET/CT is now recommended, but its role regarding bone marrow involvement is not well defined.

Berthet, of the Department of Nuclear Medicine, Centre Georges-François Leclerc, Dijon, France, and his team retrospectively enrolled 133 patients in a study to evaluate whether 18F-FDG PET/CT was useful for the detection of bone marrow involvement and predictive of outcome compared with bone marrow biopsy in persons with a new diagnosis of DLBCL. All patients had received a whole-body 18F-FDG PET/CT scan and a bone marrow biopsy from the iliac crest before receiving any treatment. As summarized in a statement from the Society of Nuclear Medicine, a final diagnosis of bone marrow involvement was made if the biopsy was positive and the positive 18F-FDG PET/CT scan was confirmed by targeted magnetic resonance imaging. If after chemotherapy, the diagnosis of bone marrow involvement was made by the concomitant disappearance of focal bone marrow uptake and uptake in other lymphoma lesions on 18F-FDG PET/CT reassessment.

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A total of 33 patients were considered to have bone marrow involvement. Within that group, 8 patients were positive according to the bone marrow biopsy, and 32 were positive according to 18F-FDG PET/CT. Compared with bone marrow biopsy, 18F-FDG PET/CT was more sensitive (94% vs 24%), showed a higher negative predictive value (98% vs 80%), and was more accurate (98% vs 81%).

Nearly half (11, or 42%) of the 26 patients with positive 18F-FDG PET/CT results and negative biopsy results were upstaged to stage IV by 18F-FDG PET/CT, which changed their treatment plans.

During follow-up (median 24 months, range 1–67 months), 29 patients (22%) experienced recurrence or disease progression, and 20 (15%) died. In multivariate analysis, only the International Prognostic Index and the 18F-FDG PET/CT bone marrow status were independent predictors of progression-free survival, and only the International Prognostic Index remained an independent predictor of overall survival.

The findings led Berthet and colleagues to conclude that assessment of bone marrow involvement with 18F-FDG PET/CT provides better diagnostic performance and prognostic stratification than does assessment with bone marrow biopsy in newly diagnosed DLBCL.