SAN FRANCISCO – Should targeted agents replace chemoimmunotherapy (CIT) as first-line treatment for chronic lymphocytic leukemia (CLL)? A recent debate suggests there’s no consensus.
Jennifer Smith/MDedge News
Dr. William G. Wierda
William G. Wierda, MD, PhD, of The University of Texas MD Anderson Cancer Center in Houston, and Jennifer R. Brown, MD, PhD, of Dana-Farber Cancer Institute in Boston, debated the topic at the National Comprehensive Cancer Network Hematologic Malignancies Annual Congress.
Dr. Wierda argued that CLL patients should receive a BTK inhibitor or BCL2 inhibitor, with or without obinutuzumab, as first-line therapy because these targeted agents have been shown to provide better progression-free survival (PFS) than CIT, and the targeted therapies may prolong overall survival (OS) as well.
Dr. Brown countered that targeted agents don’t improve PFS for all CLL patients, improved PFS doesn’t always translate to improved OS, and targeted agents cost more than CIT.
No role for CIT as first-line treatment
“We have two approaches right now, with nonchemoimmunotherapy-based treatment,” Dr. Wierda said. “One approach, with small-molecule inhibitors, is to have a sustained and durable period of disease control, particularly with BTK inhibitors. The other strategy that has emerged is deep remissions with fixed-duration treatment with BCL2 small-molecule inhibitor-based therapy, which, I would argue, is better than being exposed to genotoxic chemoimmunotherapy.”
Dr. Wierda went on to explain that the BTK inhibitor ibrutinib has been shown to improve PFS, compared with CIT, in phase 3 trials.
In the iLLUMINATE trial, researchers compared ibrutinib plus obinutuzumab to chlorambucil plus obinutuzumab as first-line treatment in CLL. At a median follow-up of 31.3 months, the median PFS was not reached in the ibrutinib arm and was 19 months in the chlorambucil arm (P less than .0001; Lancet Oncol. 2019 Jan;20[1]:43-56).
In the A041202 study, researchers compared ibrutinib alone (Ib) or in combination with rituximab (Ib-R) to bendamustine plus rituximab (BR) in untreated, older patients with CLL. The 2-year PFS estimates were 74% in the BR arm, 87% in the Ib arm, and 88% in the Ib-R arm (P less than .001 for BR vs. Ib or Ib-R; N Engl J Med. 2018; 379:2517-28).
In the E1912 trial, researchers compared Ib-R to fludarabine, cyclophosphamide, and rituximab (FCR) in younger, untreated CLL patients. The 3-year PFS was 89.4% with Ib-R and 72.9% with FCR (P less than .001; N Engl J Med. 2019 Aug 1;381:432-43).
Dr. Wierda noted that the E1912 trial also showed superior OS with Ib-R. The 3-year OS rate was 98.8% with Ib-R and 91.5% with FCR (P less than .001). However, there was no significant difference in OS between the treatment arms in the A041202 trial or the iLLUMINATE trial.
“But I would argue that is, in part, because of short follow-up,” Dr. Wierda said. “The trials were all designed to look at progression-free survival, not overall survival. With longer follow-up, we may see differences in overall survival emerging.”
Dr. Wierda went on to say that fixed‐duration treatment with the BCL2 inhibitor venetoclax can improve PFS over CIT.
In the phase 3 CLL14 trial, researchers compared fixed-duration treatment with venetoclax plus obinutuzumab to chlorambucil plus obinutuzumab in previously untreated CLL patients with comorbidities. The estimated PFS at 2 years was 88.2% in the venetoclax group and 64.1% in the chlorambucil group (P less than .001; N Engl J Med. 2019; 380:2225-36).
“[There was] no difference in overall survival,” Dr. Wierda noted. “But, again, I would argue ... that follow-up is relatively limited. We may ultimately see a difference in overall survival.”
Based on these findings, Dr. Wierda made the following treatment recommendations:
- Any CLL patient with del(17p) or TP53 mutation, and older, unfit patients with unmutated IGHV should receive a BTK inhibitor, with or without obinutuzumab.
- All young, fit patients, and older, unfit patients with mutated IGHV should receive a BCL2 inhibitor plus obinutuzumab.
Dr. Wierda also noted that ibrutinib and venetoclax in combination have shown early promise for patients with previously untreated CLL (N Engl J Med. 2019; 380:2095-2103).