Prognostic Role of Interim 18-Fluorodeoxyglucose-PET in Diffuse Large B Cell Lymphoma: Experience from a Tertiary Care Centre in North India.

This study was done to investigate the role of Interim 18-FDG-PET/CT (i-PET) in predicting the outcome of Diffuse Large B Cell Lymphoma (DLBCL) patients. The Lymphoma registry data base of the Department of Haematology was reviewed for all newly diagnosed DLBCL patients treated with R-CHOP-21 (n = 63). The PET-CT data of these patients at pre-defined time points (baseline, interim and end of treatment) was systematically collected. The predictive accuracy of i-PET-CT (done after 4 cycles R-CHOP-21 chemotherapy) was analysed to define their prognostic importance. 47 patients were eligible for final analysis in this study. According to Deauville's criteria 15 patients (31%) were positive on i-PET. The positive predictive value (PPV) of i-PET by DS was 73.3%. At a median follow up of 21 months, DS based i-PET negative and positive cases showed significant differences in 2-year OS (81.2% vs 46.7%,  = 0.007) and PFS (75% vs 26.7%,  = 0.005). Combined analysis of i-PET (by DS) and IPI showed negative predictive value (NPV) of 92.3% in Low IPI while PPV of 76.9% in high IPI subgroup of DLBCL. On a multivariate analysis of all prognostic variables, i-PET was found to be independent prognostic marker predicting outcome in DLBCL patients. i-PET is an independent prognostic marker for outcome in DLBCL patients. Combined analysis of Interim PET along with IPI score at diagnosis improves the predictive accuracy of i-PET (both PPV & NPV) and may guide tailoring of therapy in these patients.