Consolidation anti-CD22 fractionated radioimmunotherapy (RIT) with 90Y-epratuzumab tetraxetan following R-CHOP in front-line therapy of elderly, disseminated, diffuse large B-cell lymphoma (DLBCL) patients: Predictive value of FDG PET

Objectives To assess predictive value of PET in the evaluation of 6 X R-CHOP14 followed by 90Y-epratuzumab tetraxetan consolidation in front-line therapy of DLBCL patients (pts) > 60 yrs old, enrolled in a phase II trial.

Methods PET was performed at baseline, after 3X and 6X R-CHOP, and after RIT according to the International Harmonization Project (IHP) criteria using mediastinum as reference. Predictive value on progression-free survival (PFS) of LDH, aaIPI, Ann Arbor stage, PS, general signs, bulky, bone marrow/spleen/organ disease, CT-based International Workshop Response Criteria [IWRC] (complete response CR/unconfirmed CR vs no CR/CRu) and PET (- vs +) at the different time-points were assessed.

Results 75 pts were enrolled, 61 treated by RIT; median follow-up was 27.5 mos (1 to 46). PET was + in 37/73 assessed pts (50.1%) after 3X R-CHOP and in 30/71 (42.3%) after 6X R-CHOP; 26 of these 30 PET+ pts received RIT and 13/26 (50%) became PET-, resulting in 75.4% (46/61) PET- after RIT. Univariate analysis showed that PET at 3X and 6X R-CHOP did not predict PFS; PET after RIT was predictive (p=0.006) as were LDH (p<0.001), aaIPI (p=0.036), and IWRC after RIT (p<0.001). Multivariate analysis showed that only PET and IWRC after RIT remained predictive (p=0.005 and p=0.041, respectively); 2-yr-PFS was 88.5% in PET- and 57.1% in PET+ pts.

Conclusions This study showed an independent predictive value of PET after RIT. Interim PET did not predict PFS but IHP criteria are not recommended for early evaluation. No predictive value was found for PET after 6X R-CHOP, in contrast to other studies, suggesting benefits of RIT consolidation.