Role Of Interim,-PET In Poor Prognosis Young Patients With Diffuse Large B Cell Lymphoma At Diagnosis: Data From An Ancillary Study Of a Prospective Randomized Phase III Study (DLCL04) From the Fondazione Italiana Linfomi

The role of interim-PET (i-PET), after two cycles of chemotherapy, in advanced stage Hodgkin's lymphoma is well defined; the same role in diffuse large B cell lymphoma (DLBCL) is still controversial. The Fondazione Italiana Linfomi planned a prospective randomized phase III trial, addressed to young poor prognosis DLBCL patients at the diagnosis, with a 2x2 factorial design aimed at investigating the possible benefit of intensification with R-HDC+ASCT after R-dose-dense chemotherapy delivered at two different level of dose (R-CHOP14/R-MegaCHOP14). During this study an ancillary study was designed to define the prognostic impact of i-PET on progression free survival (PFS) after two cycles of immunochemotherapy in all treatments arms.

As described by Vitolo et al (oral communication, abs 688 ASH 2012), patients were stratified according to aa-IPI and randomized at diagnosis to receive: R-CHOP14 x 8 cycles; R-MegaCHOP14 (1200 mg/sqm Cyclophosphamide, 70 mg/sqm Doxorubicin, standard dose Vincristine and Prednisone) x 6; R-CHOP14 x 4 + R-HDC (Rituximab + High Dose Cytarabine + Mitoxantrone + Dexamethasone) followed by BEAM and ASCT; R-MegaCHOP14 x 4 + R-HDC + BEAM and ASCT. G-CSF support was mandatory. Seventeen centers agreed to participate in the study and enrolled patients. All evaluable patients had performed basal PET and i-PET. A visual dichotomous criteria, according to Deauville Criteria (First Consensus Conference, 2009), was used to define the i-PET result. The final response was identified according to 2007 Cheson response criteria.

From June 2005 to September 2010, 399 patients were randomized in the overall DLCL04 study and 130 were enrolled for the ancillary PET study , 69 in the R-HDC+ASCT and 61 in R dose dense therapy respectively. The clinical characteristics, as in the overall DLCL04 study, were well balanced among the four arms of therapy excluding a selection bias in the group of patients studied with i-PET. The i-PET result was positive in 74 patients and negative in 56 patients, no differences were observed between negative and positive i-PET results according to clinical characteristics and group of treatment. In particular, in R-dose dense arm 27 were negative and 34 positive, in R-HDC+ASCT 29 were negative and 40 positive, according to immunochemotherapy scheme in R-CHOP14 29 were negative and 40 were positive, in MegaCHOP14 27 were negative and 34 were positive. With a median follow-up of 36 months, 3-year PFS and 3-year Overall Survival (OS) rates for the whole series were: 64% (95% CI:59-69) and 79% (95% CI:74-83) respectively. No differences in PFS was reported according to i-PET result. In particular 3-year PFS were 87%(95% CI:75-94) in i-PET negative patients and 76% (95% CI: 65-85) in i-PET positive patients respectively (p: 0.09 The 3-year PFS according to I- PET results in the different treatment arm were: in the R-HDT+ASCT group i-PET negative or i-PET positive patients had a 3-year PFS of 83% (95% CI:63-92) and 79% (95% CI:63-89) respectively; in the R-dose dense i-PET negative or i-PET positive patients had a 3-year PFS of 92% (95% CI:73-98) and 72% (95% CI:54-85) with a p value near the significance (0.07). According to OS, i-PET negative and i-PET positive patients had a 3-year OS of 89%(95% CI:76-95) and 83%(95% CI:72-90) respectively, p=0.219.

In our multicenter prospective study, addressed to young poor prognosis DLBCL patients at the diagnosis, i-PET, performed after two immunochemotherapy cycles and analyzed with a visual method, is not able to identify two different risk population. To confirm our data, we are planning in the near future a centralized revision of all evaluable PET. In conclusion, our feeling is that the i-PET after two cycles in poor prognosis DLBCL patients is too early to predict a chemorefractory disease and more parameters must be considered to define clinical response in these patients.

No relevant conflicts of interest to declare.