FDG-PET for lymphoma staging fails to top bone marrow biopsy

Years of research and dozens of papers probing PET's might in staging lymphoma have yielded sizable data showing that it does not supersede bone marrow biopsy. Clinicians who choose to replace biopsy with FDG-PET could potentially miss a high number of cases of infiltrative disease, according to a study published in the June issue of the Journal of Nuclear Medicine.

Bone marrow infiltration in patients with lymphoma signifies advanced-stage disease. Accurate staging is critical, and the presence of infiltration may affect treatment and prognosis. Bone marrow biopsy, the diagnostic standard, is invasive, painful, and sometimes inconclusive. PET imaging, while noninvasive and pain-free, cannot lay claim to better results.

A meta-analysis of the clinical literature found that FDG-PET has moderately good, but not excellent, concordance with biopsy. Most of the studies analyzed had small sample sizes, however, and researchers are calling for larger studies to validate PET in this patient population.

Dr. Emilios E. Pakos and colleagues at the University of Ioannina School of Medicine in Greece searched the Medline and Embase databases for studies that included FDG-PET and bone marrow biopsy to stage patients with primary lymphoma or recurrent lymphoma after complete remission.

Rigorous inclusion criteria winnowed the available studies down to 13. The total number of patients was 587, including those with Hodgkin's disease and non-Hodgkin's lymphoma.

PET's overall sensitivity and specificity were 51% and 91%, respectively. Half of the cases with positive bone marrow biopsies failed to show FDG uptake. But a negative PET scan agreed with a negative biopsy in more than 90% of cases. Researchers found that positive PET in the presence of negative biopsy had a high likelihood of being a true positive. The missed bone marrow involvement often could be documented with a second biopsy directed at the site of the positive PET signal.

Subgroup analysis showed that PET was sensitive for Hodgkin's disease, but few patients in these studies with Hodgkin's had bone marrow involvement. While encouraging, the finding needs to be verified by larger studies that include various levels of bone marrow infiltration.

Overall, PET was moderately sensitive for non-Hodgkin's lymphoma but showed very good detection of infiltration with aggressive types of the disease.

Researchers do not recommend routinely replacing biopsy with PET to stage lymphoma. PET could complement bone marrow biopsy and could occasionally identify additional cases of focal bone marrow involvement.

Future research should address whether the complementary data have significant impact on patient prognosis, the authors concluded.

For more information from the Diagnostic Imaging archives:

Reducing uncertainty

SPECT strengths hold up against PET for long term

PET/CT attains slight edge over PET for lymphoma staging

FDG-PET improves management of lymphoma patients