Diffuse large B-cell lymphoma involving osseous sites: utility of response assessment by PET/CT and good longterm outcomes.

Osseous involvement by diffuse large B-cell lymphoma (DLBCL-bone) is a heterogeneous disease. There is limited data regarding response assessment by positron emission tomography with fluorodeoxyglucose, which may demonstrate residual avidity despite a complete response. We analyzed clinical data of patients with newly diagnosed DLBCL and identified all cases with DLBCL-bone. End of treatment scans were reviewed by two independent experts classifying osseous lesions into Deauville (DV) ≤3; DV ≥4, or reactive uptake in the bone marrow (M), site of fracture (F) or surgery (S). We compared outcomes of DLBCL-bone to other extranodal sites (EN) matched on International Prognotic Index features and regimen. Of 1,860 patients with DLBCL (bone 16%; EN 45%; nodal 39%), 41% had localized disease and 59% advanced. Only 9% (n=27) of patients with initial bone involvement had residual fluorodeoxyglucose avidity at the osseous site. In half of these cases, the uptake was attributed to F/S/M, and of the remaining 13, only two were truly refractory (both with persistent disease at other sites). Overall survival and progression-free survival (PFS) were found to be similar for early- stage nodal DLBCL and DLBCL-bone, but inferior in EN-DLBCL. Advanced-stage disease involving the bone had a similar 5-year PFS to nodal disease and EN-DLBCL. After matching for International Prognotic Index and treatment regiments, PFS between bone and other EN sites was similar. Osseous involvement in DLBCL does not portend a worse prognosis. End of treatment DV ≥4 can be expected in 5-10% of cases, but in the absence of other signs of refractory disease, may be followed expectantly.

Prospective Study of 3'-Deoxy-3'-18F-Fluorothymidine PET for Early Interim Response Assessment in Advanced-Stage B-Cell Lymphoma.

UNLABELLED: Current clinical and imaging tools remain suboptimal for early assessment of prognosis and treatment response in aggressive lymphomas. PET with 3'-deoxy-3'-(18)F-fluorothymidine ((18)F-FLT) can be used to measure tumor cell proliferation and treatment response. In a prospective study in patients with advanced-stage B-cell lymphoma, we investigated the prognostic and predictive value of (18)F-FLT PET in comparison to standard imaging with (18)F-FDG PET and clinical outcome. METHODS: Sixty-five patients were treated with an induction/consolidation regimen consisting of 4 cycles of R-CHOP-14 (rituximab, cyclophosphamide, doxorubicin, vincristine, prednisone) followed by 3 cycles of ICE (ifosfamide, carboplatin, etoposide). (18)F-FLT PET was performed at baseline and at interim (iPET) after 1-2 cycles of therapy. (18)F-FDG PET was performed at baseline, after cycle 4, and at the end of therapy. The relationship between PET findings, progression-free survival (PFS) and overall survival (OS) was investigated. RESULTS: With a median follow-up of 51 mo, PFS and OS were 71% and 86%, respectively. (18)F-FLT iPET, analyzed visually (using a 5-point score) or semiquantitatively (using SUV and ΔSUV) predicted both PFS and OS (P < 0.01 for all parameters). Residual (18)F-FLT SUVmax on iPET was associated with an inferior PFS (hazard ratio, 1.26, P = 0.001) and OS (hazard ratio, 1.27, P = 0.002). When (18)F-FDG PET was used, findings in the end of treatment scan were better predictors of PFS and OS than findings on the interim scan. Baseline PET imaging parameters, including SUV, proliferative volume, or metabolic tumor volume, did not correlate with outcome. CONCLUSION: (18)F-FLT PET after 1-2 cycles of chemotherapy predicts PFS and OS, and a negative (18)F-FLT iPET result may potentially help design risk-adapted therapies in patients with aggressive lymphomas. In contrast, the positive predictive value of (18)F-FLT iPET remains too low to justify changes in patient management.