Rod Humerickhouse discusses the importance of Minimal Residual Disease Negativity.
Background: The multinational, open-label, phase 3 CLL14 trial compared fixed-duration targeted VenG treatment with chlorambucil-obinutuzumab (ClbG) in previously untreated pts with CLL and comorbidities. Here we present endpoint analyses with particular emphasis on MRD? and PFS. Methods: Pts with a CIRS score >6 and/or an estimated creatinine clearance <70 mL/min were randomized 1:1 to receive equal duration treatment with 12 cycles (C) of standard Clb or Ven 400 mg daily in combination with G for first 6 C. Primary endpoint was PFS. MRD? in peripheral blood (PB) or bone marrow (BM) 3 months (mo) after treatment completion was a key secondary endpoint. MRD was analyzed serially from C4 every 3 mo by an allele-specific oligonucleotide polymerase chain reaction assay (ASO-PCR; cut-off, 10-4) and by next generation sequencing (NGS; cut-offs, 10-4, 10-5,10-6). Results: 432 pts were enrolled; 216 in each treatment group (intent-to-treat population). After 29 mo median follow-up, superior PFS was observed with VenG vs ClbG (HR 0.35; 95% CI 0.230.53; P<0.0001). MRD? by ASO-PCR was significantly higher with VenG vs ClbG in both PB (76% vs 35% [P<0.0001]) and BM (57% vs 17% [P<0.0001]) 3 mo after treatment completion. Overall, 75% of VenG MRD-negative pts in PB were also MRD-negative in BM vs 49% in the ClbG group. Landmark analysis for this timepoint by PB MRD status showed that MRD? was associated with longer PFS. Higher MRD? rates were achieved early and were more sustainable with VenG: 81% (VenG) vs 27% (ClbG) of pts were MRD-negative 12 mo after treatment completion; HR for MRD conversion 0.19; 95% CI 0.120.30 (median time off-treatment: 19 mo). MRD? rates by NGS confirmed these results; 78% (VenG) vs 34% (ClbG) of pts had MRD? at <10-4, 31% vs 4% at <10-6 and 35% vs 15% at ?10-6<10-5, respectively. Conclusions: Fixed-duration VenG induced deep (<10-6 in 1/3 of pts), high, and long lasting MRD? rates (with a low rate of conversion to MRD+ status 1 year after treatment) in previously untreated pts with CLL and comorbidities, translating into improved PFS