The role of PET/CT in the evaluation of bone marrow involvement in the primary staging of Lymphoma

Bone marrow involvement is an important parameter that affects the stage, prognosis and the management of lymphoma patients.The aims of our study are; to determine the role of PET/CT in the assessment of bone marrow involvement in the primary staging of lymphoma patients using different quantitative measurement methods, to determine the most accurate quantitative measurement method, to reinterpret bone marrow biopsies using FISH method to improve the accuracy of PET/CT in detection of bone marrow involvement and to investigate the effects of laboratory and clinical findings on the accuracy of PET/CT.Primary lymphoma patients who have their PET/CT imaging and bone marrow biopsies done in Gazi University Medical Hospital were included in this study. Using PET/CT data, bone marrow SUVmean, bone marrow to liver SUVmean ratio, bone marrow to blood pool SUVmean ratio and bone marrow to serebellum SUVmean ratio values were obtained. Pathology reports, laboratory and clinical findings of the patients were recorded retrospectively. FISH was used to evaluate mature B cell lymphoma patients using BCL2, BCL6, MYC and PAX5 probs.Fifteen bone marrow biopsies were positive with routine histopathological examinations. FISH method didn?t increase the total number of the patients with bone marrow involvement. Two patients have positive bone marrow biopsies with FISH examination. There is no significant difference between the quantitative measurement methods of PET/CT in respect to detection of bone marrow involvement. However we decided that bone marrow to liver SUVmean ratio (BM/L SUV) is a suitable criterion to assess bone marrow involvement of primary lymphoma patients. Optimum cut off value for BM/L SUV ratio was found to be 1.8. Using this cut off value sensitivity, specificity, PPV and NPV of PET/CT is %53, %90, %53 and %90, respectively. In a selected subgroup of patients with aggressive lymphoma these values improved to %83, %97, %83 and %97, respectively. Using this cut off value, among patients with false negative results indolant lymphoma patients and patients with low lymph node SUVmax were more frequent. There is no significant laboratory difference (Sed, CRP, WBC, % Neutrophil) between patients with false positive and true positive results.In conclusion, PET/CT had a high negative predictive value. Therefore in the primary evaluation of aggressive lymphoma patients with normal bone marrow PET/BT findings, PET/BT is a noninvasive alternative over bone marrow biopsy.