P031 | PROGNOSTIC VALUE OF SEMI-QUANTITATIVE METABOLIC PARAMETERS ON [18F]FDG PET/CT IN PATIENTS WITH DIFFUSED LARGE B CELL LYMPHOMA AT DIAGNOSIS

Diffuse large B-cell lymphoma (DLBCL) represents the most common subtype of non-Hodgkin lymphoma (NHL). After first-line therapy with rituximab, cyclophosphamide, doxorubicin, vincristine, prednisone (R-CHOP), 30% of patients have relapsed or refractory disease. Recent studies showed that semiquantitative volume parameters on pre-treatment 18F-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) could represent variables with prognostic influence. We aimed to determine the prognostic impact of these metabolic parameters in patients with DLBCL receiving first-line therapy. In this observational study, we have retrospectively analyzed a cohort of 53 consecutive patients, treated between 2016 and 2022. Diagnosis was made according to WHO 2016 classification. PET/CT scan was performed according to the 2014 European Association of Nuclear Medicine and Molecular Imaging guidelines version 2.0. Semiquantitative metabolic parameters, assessed by LIFEx (www.lifexsoft.org), included total metabolic tumor volume (TMTV), total lesion glycolysis (TLG), Dmax and DmaxVox. TMTV was calculated using the fixed threshold of SUV4. Moreover, we assessed IPI and IMPI score in all cases. All cases received R-CHOP/CHOP-like regimens with curative intent. Treatment response was assessed according to the 2014 Lugano classification criteria. Out of 53 patients, IPI score was 3-5 for 32.1% ot total cases (17/53). Interestingly, IMPI score was low in 43/53 cases (81.1%) and only 1 case had high-risk disease. CR was achieved in 49/53 patients (92.4%), 7/53 (13.2%) relapsed after achieving a CR. For the entire cohort, 2-y PFS and OS were 84.9 and 90.6%, respectively, while 5-y PFS and OS were 65.5% and 77.6%, respectively. In univariate analysis, IPI score, B symptoms, TMTV (with best cut-off value assessed by ROC curve), Dmax and DmaxVox were associated with reduced PFS (Table 1). IPI score was the only variable for which we showed a significant association with reduced OS. None of the variables maintained its significance in multivariate analysis. At last follow-up, 43/53 patients were alive, causes of death included progressive disease (4 cases), death of unknown origin while in CR (3 patients, aged >80 years), infectious complications (2 cases), and secondary acute myeloid leukemia (1 case). In conclusion, the semi-quantitative metabolic parameters of PET/CT at diagnosis are proposed as innovative elements capable of interpreting the burden and dissemination of DLBCL and predicting survival.