Comparison of clinical and PET-derived prognostic factors in patients with non-Hodgkin lymphoma: A special emphasis on bone marrow involvement

Objective In patients with non-Hodgkin lymphoma (NHL), we investigated ¹⁸F FDG PET/computed tomography (CT) parameters, clinical findings, laboratory parameters, and bone marrow involvement (BMI) status for predictive methods in progression-free survival (PFS) and overall survival (OS), and whether ¹⁸F FDG PET/CT could take the place of bone marrow biopsy (BMB). Methods The performance of ¹⁸F FDG PET/CT (BM_PET) was evaluated. The prognostic value of maximum standardized uptake value (SUVmax), metabolic tumor volume (MTV), stage, international prognostic index (IPI) score, IPI risk, lactate dehydrogenase (LDH), B2 microglobulin, Ki67 proliferation index, and the presence of BMI was evaluated for OS and PFS. Kaplan-Meier curves were drawn for each designated cutoff value, and 5-year PFS and 7-year OS were evaluated using log-rank analysis. Results The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and accuracy of BM_PET and BMB to identify BMI were 69, 100, 86.1, 80, 100%, and 81.6, 100, 92.5, 89, 100%, respectively. The sensitivity, specificity, PPV, NPV, and accuracy of BM_PET in patients with Ki67- proliferation index >25% were all 100%. BM_PET, IPI risk, MTV, and LDH were found to be independent prognostic predictors for PFS, whereas BM_PET, SUVmax, and MTV for OS. Five-year PFS analysis estimated as follows: BM_PET (+) = 22%, BM_PET (-) = 80%, LDH ≤ 437 (U/L) = 86%, LDH > 437 (U/L) = 51%, MTV ≤ 56 (cm³) = 87%, MTV > 56 (cm³) = 49%, low IPI risk = 87%, intermediate IPI risk = 69%, high IPI risk = 25%. Seven-year OS analysis was found as: SUVmax ≤ 17.6 = 80%, SUVmax > 17.6 = 48%, MTV ≤ 56 (cm³) = 84.4%, MTV > 56 (cm³) = 45.8%, BM_PET (-) = 72.5%, BM_PET (+) = 42%. Conclusion In the Ki-67 proliferation index > 25% group, ¹⁸F FDG PET/CT was able to differentiate BMI independently from NHL subgroups. We recommend using this method with large patient groups. MTV and BM_PET were independent prognostic indicators for OS and PFS and may help to determine high-risk patients.