Exploring the role of FDG-PET in the assessment of bone marrow involvement in lymphoma patients as interpreted by qualitative and semiquantitative disease metabolic activity parameter.

ABSTRACT

Bone marrow biopsy (BMB) is currently the standard method to evaluate marrow involvement in malignant lymphomas. However, there exist a number of pitfalls in this technique that can have important implications for initial staging, prognostification, and treatment of the disease. The present study was undertaken to investigate the utility of FDG-PET imaging in the detection of bone marrow involvement in untreated lymphoma patients. Forty untreated patients (36 males and 12 females) with either Hodgkin's disease (HD) (n = 17) or non-Hodgkin's lymphoma (NHL) (n = 31) underwent whole body FDG-PET study for disease evaluation. Bone marrow uptake of FDG was graded as absence or presence of disease activity at marrow sites by qualitative assessment. Semiquantitative analysis involved deriving disease metabolic index (DMI) using the following formula DMI = SUV max of suitable circular ROI over PSIS or trochanteric region/ SUVmax of similar ROI over adjoining background. Findings of BMB and FDG-PET were compared for final analysis. Eleven out of 17 HD patients (12 males and 5 females) demonstrated concordance between FDG PET findings and BMB reports. Remaining 6 cases showed discordance of FDG-PET demonstrating presence of marrow involvement at marrow sites and uninvolved marrow on BMB. Twenty six of the 31 NHL cases (24 males and 7 females) demonstrated concordance between FDG PET findings and BMB reports. Remaining 5 cases showed discordance of FDG-PET demonstrating presence of marrow involvement at marrow sites and uninvolved marrow on BMB. All the BMB positive patients (2 of HD and 5 of NHL) demonstrated disease activity in bone marrow on FDG-PET study. All patients with absence of disease activity at marrow sites on FDG-PET scan (9 of HD and 21 of NHL) had histology proven uninvolved marrow. The quantitative assessment by DMI showed a mean of >2.5 in HD and NHL patients at the PSIS region and the trochanteric region bilaterally in cases of bone marrow involvement by the disease. FDG-PET is a useful adjuvant to BMB for the evaluation of bone marrow involvement in lymphoma patients. The disease metabolic index of >2.5 at the marrow sites can serve as a semiquantitative parameter for such diagnosis on FDG-PET in untreated patients of lymphoma.