1013P - The role of FDG-PET/CT in detecting bone marrow involvement in diffuse large b-cell lymphoma

Abstract

Background: The sensitivity and prognostic value of FDG-PET/CT in the staging of Diffuse Large B-Cell lymphoma (DLBCL) remain unclear. PET/CT provides a high level of accuracy for identifying focal skeletal marrow disease in Hodgkin's lymphoma (HL). Whether the omission of staging Bone Marrow Biopsy (BMB) would change treatment strategy of DLBCL is not known. Methods: We retrospectively studied 114 patients with DLBCL from three rural community oncology practices in New Mexico between January 96- September 2016. Patients receiving BMB and PET/CT were included. Descriptive statistics and Chi-square methods were used to evaluate associations. Results: Mean age at diagnosis was 66 years (23-92), 54% were males, 82% received RCHOP therapy. Out of 114 patients, 27 (23%) patients did not have a staging BM biopsy. The sensitivity of PET/CT scan was 73% and Specificity 87%. Positive predictive value (PPV) 50% and Negative predictive value (NPV) 95%. Patients with positive focal PET/CT were more likely (50% vs 5%), χ2 (1, N = 74) = 19.9, (p < 0.001) to have a positive BMB in comparison those with negative PET/CT scan. There was correlation of bone marrow involvement with clinical stage IV (31%), III (13%), II (5%), I (0%), χ2 (1, N = 74) = 10.14, (p = 0.02) and IPI score: High (14%), Int-High (40%), Low-Int (10%), Low (3%) %), χ2 (1, N = 74) = 10.7, (p = 0.019). Cytopenia was not associated with BM involvement χ2 (1, N = 74) = 1.37, (p = 0.242). The 5-year OS for PET/CT positive vs BM involved (38% [95%CI 14-61] vs 31% [95CI% 5-56] p = 0.69), and PET/CT negative vs BM uninvolved patients (44% [95%CI 32-55] vs 50% [95%CI 38-61] p = 0.46) were not statistically different. Conclusions: PET/CT is valuable as having a high negative predictive value for detection of focal marrow involvement in DLBCL. This may help avoid BMB, especially if clinically early stage disease. Cytopenia did not predict marrow involvement. The long-term prognostic value of PET/CT is similar to that obtained by a bone marrow biopsy. Legal entity responsible for the study: Kymera Independent Physicians Funding: None Disclosure: All authors have declared no conflicts of interest.