PS1081 UTILITY OF BONE MARROW BIOPSY IN POSITRON EMISSION TOMOGRAPHY‐STAGED PATIENTS WITH DIFFUSE LARGE B‐CELL LYMPHOMA
Authors: Grech M. , Giotas A. , Camilleri D.‐J. , Gatt A. 
Published: June 2019

Background:Detection of bone marrow involvement (BMI) is of paramount importance in the assessment of lymphoma. The traditional method of detecting BMI is by bone marrow biopsy (BMB) from the iliac crest. 18F‐fluorodeoxyglucose positron emission tomography‐computed tomography (PET‐CT) has become the standard imaging investigation for DLBCL. PET‐CT has proved to be very sensitive in detecting extra‐nodal disease, including BMI and it frequently results in upstaging of patients when compared to CT alone.Aims:The purpose of this study is to establish the degree of concordance between PET‐CT and BMB for the detection of BMI in DLBCL and to assess whether PET‐CT can replace BMB in these patients.Methods:Patients diagnosed with DLBCL between January 2010 and December 2018 were retrospectively identified. All patients were treated with rituximab‐based chemotherapy regimens. Only patients who had both BMB and PET‐CT at baseline staging were included in the analysis. Results of BMB and PET‐CT were collected from the original reports. The prognostic impact of BMI on overall survival (OS) was assessed and Cox regression analysis was performed to adjust for R‐IPI risk factors.Results:Two hundred and ninety‐three patients with DLBCL were identified during the study period. Sixty‐three patients did not have a BMB performed while 109 patients did not have a PET‐CT scan. One hundred and sixty‐eight patients underwent both investigations and were included in the analysis. The median age of the study population was 64 years (range 18–88 years). Forty‐four patients (26.2%) had skeletal lesions detected by PET‐CT while BMI by lymphoma was detected on trephine in 19 patients (11.3%). In the 44 patients with PET‐CT defined BMI, BMB was positive in 15 patients (34.1%) while it was negative in 29 patients (65.9%). In these 29 patients the pattern of PET‐CT uptake was focal in 27 (93.1%) and diffuse in 2 (6.9%). In the 124 patients with no evidence of BMI on PET‐CT, BMB was negative in 120 patients (96.8%) and positive in 4 patients (3.2%). Out of these, three patients had BMI by low‐grade lymphoma while one patient had BMI by DLBCL. The degree of concordance between PET‐CT and BMB was 80.4%. For BMB the sensitivity for detection of BMI was 39.6% (95% CI: 25.8%–54.7%), specificity 100% (95% CI: 97.0%–100%), positive predictive value (PPV) 100%, negative predictive value (NPV) 80.5% (95% CI: 76.7%–83.9%) and diagnostic accuracy (DA) 82.7% (95% CI: 76.2%–88.1%). For PET‐CT the sensitivity was 91.7% (95% CI: 80.0%–97.7%), specificity 100% (95% CI: 97.0%–100%), PPV 100%, NPV 96.8% (95% CI: 92.2%–98.7%) and DA 97.6% (95% CI: 94.4%–99.4%).There was a significant difference in OS between the patients with BMI and those without (5‐year OS 29% vs 66%, P = 0.003). However, the prognostic significance of BMI was no longer retained on multivariate analysis when controlling for the R‐IPI (HR 1.72; 95% CI: 0.90–3.29, P = 0.1).Summary/Conclusion:The study shows that a significant number of patients showed discrepancy between the results of PET‐CT and BMB in detecting BMI in DLBCL. Most discrepancies were as a result of PET‐CT being positive with BMB being negative. However, PET‐CT still missed four cases of BMI that were detected on BMB. Most of these patients had BMI by low‐grade lymphoma. Considering these findings, PET‐CT still cannot reliably replace BMB for the routine staging of patients with DLBCL.