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Is CLL chemoimmunotherapy dead? Not yet



– Chemoimmunotherapy for chronic lymphocytic leukemia is on the way out, but there’s one scenario where it still plays a key role, according to one leukemia expert.

That scenario is not in relapsed or refractory chronic lymphocytic leukemia (CLL), where the use of fludarabine, cyclophosphamide, and rituximab (FCR) may be hard to justify today. Data supporting use of FCR in relapsed CLL show a median progression-free survival (PFS) of about 21 months, Susan M. O’Brien, MD, of the University of California, Irvine, said at the annual meeting of the American Society of Clinical Oncology. There is also data for bendamustine-rituximab retreatment showing a median event-free survival of about 15 months, she added.

By contrast, the 5-year follow-up data for the Bruton tyrosine kinase inhibitor ibrutinib in the relapsed/refractory setting shows a median PFS of 52 months, which is “extraordinary,” given that the patients had a median of four prior regimens, Dr. O’Brien said.

Similarly, recently published results from the randomized, phase 3 MURANO study of venetoclax plus rituximab in relapsed/refractory CLL showed that median PFS was not reached at a median follow-up of 23.8 months, versus a median of 17 months for the bendamustine-rituximab comparison arm (N Engl J Med. 2018;378[12]:1107-20).

“Thanks to the MURANO study, we likely will have an expanded label for venetoclax that includes the combination of venetoclax and rituximab,” Dr. O’Brien said. “I think it’s quite clear that either of these is dramatically better than what you get with retreatment with chemotherapy, so I personally don’t think there is a role for chemoimmunotherapy in the relapsed patient.”

On June 8, 2018, the Food and Drug Administration granted regular approval for venetoclax for patients with CLL or small lymphocytic lymphoma, with or without 17p deletion, who have received at least one prior therapy. The FDA also approved its use in combination with rituximab.*

But frontline CLL treatment is currently a little bit more complicated, Dr. O’Brien said.

Recent studies show favorable long-term outcomes with FCR frontline therapy in the immunoglobulin heavy chain variable gene (IgHV) –mutated subgroup of patients, she noted.

The longest follow-up comes from a study from investigators at the University of Texas MD Anderson Cancer Center, Houston, published in 2016. In that study, the 12.8-year PFS was 53.9% for IgHV-mutated patients, versus just 8.7% for patients with unmutated IgHV. Of the IgHV-mutated group, more than half achieved minimal residual disease (MRD) negativity after treatment (Blood. 2016 Jan 21; 127[3]: 303-9).

“I’m going to go out on a limb and I’m going to suggest that I think there is a cure fraction here,” Dr. O’Brien said. “On the other hand, if there’s not a cure fraction and they’re going to relapse after 17 years, that’s a pretty attractive endpoint, even if it’s not a cure fraction.”

Clinical practice guidelines now recognize IgHV mutation status as an important marker that should be obtained when deciding on treatment, Dr. O’Brien noted.

For unmutated patients, the RESONATE-2 trial showed that ibrutinib was superior to chlorambucil in older patients, many of whom had comorbid conditions. In the 3-year update, median PFS was approximately 15 months for chlorambucil, while for ibrutinib the median PFS was “nowhere near” being reached, Dr. O’Brien said.

Those data may not be so relevant for fit, unmutated patients, and two randomized trials comparing FCR with bendamustine and rituximab have yet to report data. However, one recent cross-trial comparison found fairly overlapping survival curves for the two chemoimmunotherapy approaches.

Dr. O’Brien said she would put older patients with comorbidities on ibrutinib if a clinical trial was not available, and for fit, unmutated patients, while more data are needed, she would also use ibrutinib. However, patient preference sometimes tips the scale in favor of FCR.

“The discussions sometimes are quite long about whether the patient should opt to take ibrutinib or FCR,” Dr. O’Brien said. “The last patient I had that discussion with elected to take FCR. When I asked him why, he said because he liked the idea of being finished in six cycles, off all therapy, and hopefully in remission.”

While Dr. O’Brien said she views chemoimmunotherapy as still relevant in IgHV-mutated patients, eventually it will go away, she concluded. Toward that end, there is considerable interest in venetoclax plus ibrutinib, a combination that, in early reports, has yielded very encouraging MRD results in first-line CLL.

“We have no long-term data, but very, very exciting MRD negativity data,” Dr. O’Brien said.

Dr. O’Brien reported relationships with Abbvie, Amgen, Celgene, Gilead Sciences, Janssen, Pfizer, Pharmacyclics, Sunesis Pharmaceuticals, and others.

*This story was updated 6/25/2018.

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