“There’s not a lot of awareness about the fact that you’re probably better off not permanently discontinuing treatment,” Anthony R. Mato, first author of the research published in Haematologica, said in an interview.
“Instead, attempting dose reductions with later resumption to complete the planned schedule for treatment probably could improve outcomes,” said Dr. Mato, who is director of the CLL Program at Memorial Sloan Kettering Cancer Center in New York.
Venetoclax, a potent B-cell lymphoma-2 (BCL2) inhibitor, provides a novel, chemotherapy-free treatment option for first-line and r/r CLL. While its safety profile is manageable, treatment interruptions are very common, and premature discontinuations are reported in about a third of patients, often because of adverse events.
Lacking data on the effects of those interruptions on survival outcomes, Dr. Mato and colleagues conducted a post hoc analysis of the phase 3 MURANO trial. In this open-label study, treatment with six cycles of venetoclax in combination with rituximab followed by venetoclax once daily for a total of 2 years showed superior progression-free survival, compared with six cycles of bendamustine plus rituximab in patients with r/r CLL (P < .0001).
The current analysis involved 194 intention-to-treat patients from the trial’s venetoclax arm, among whom 140 (72%) completed 2 years of therapy, and 54 (28%) prematurely discontinued treatment. The most common reasons for discontinuation were adverse events (53.7%) and disease progression (22.2%).
Among those with early discontinuation for any reason except disease progression, the rate of progression-free survival was significantly inferior, compared with those who completed the treatment (hazard ratio, 5.98; P < .0001), as was the rate or discontinuation caused specifically by adverse events, which most commonly involved neutropenia or thrombocytopenia (HR, 5.82; P < .0001).
Those who discontinued had a mean duration of venetoclax therapy of 11.3 months, compared with 24.4 months for all patients. For each additional month of venetoclax therapy, there was a significantly lower risk of a progression-free survival event (P = .0263) and of an overall survival event (P < .0001).
The treatment interruption rate was much higher, at 69% (134), involving neutropenia in 43% (84) of instances and requiring dose reductions in 23% (45) of cases.
However, in contrast to permanent discontinuations, the temporary interruptions and dose reductions had no significant effect on progression-free or overall survival, regardless of the duration.
“Improved progression-free and overall survival were associated with greater cumulative venetoclax treatment exposure,” the authors wrote.
“The results of these analyses highlight the importance of appropriately managing treatment modifications to ensure optimal outcomes for patients receiving targeted treatment for CLL,” they said.
Key measures including “better supportive care, use of growth factors, and more aggressive strategies for dose reduction could potentially help to improve or decrease the number of patients discontinuing due to an adverse event,” Dr. Mato added.“We can’t say definitively because this is not a randomized study – it’s a retrospective analysis from a randomized study – but those measures likely could have a positive impact on patient outcomes.”
The study received support from Genentech and AbbVie. Dr. Mato reported consulting or other relationships with AbbVie, AstraZeneca, Celgene, DTRM, Genentech, Janssen, Loxo, PCYC, Sunesis, and TG Therapeutics.