Discontinuing ibrutinib therapy because of disease progression was associated with worse survival, according to a real-world study of ibrutinib dosing in chronic lymphocytic leukemia (CLL) and non-Hodgkin lymphoma patients.
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Researchers at the University of Rochester Wilmot Cancer Institute in New York, who performed the single-center study, also found that optimal dosing early on in treatment has a significant impact on disease progression.
“Treating physicians need to be aware of these outcomes when initiating therapy on patients with high-risk CLL or lymphoma, as well as those with significant comorbidities or immune deficiencies,” AnnaLynn M. Williams. MS, and her colleagues reported in Clinical Lymphoma, Myeloma and Leukemia.
The researchers examined the impact of ibrutinib discontinuation and dose adherence on overall and progression-free survival in 170 patients with non-Hodgkin lymphoma and CLL treated with the drug at the Wilmot Cancer Institute between Jan. 1, 2014, and Dec. 1, 2016.
The study comprised 115 patients with CLL, 23 patients with Waldenstrom macroglobulinemia, 21 patients with mantle cell lymphoma, and 11 patients with other non-Hodgkin lymphomas. The median age of patients who started ibrutinib was 68 years, and the median treatment duration was 14.3 months. About a third of patients were taking ibrutinib as a first-line treatment.
Overall, 51 patients (30%) permanently discontinued ibrutinib during the study period, with more than half of the discontinuations stemming from adverse events or comorbidities. About 35% of the discontinuations were due to disease progression.
Median overall survival after discontinuation due to disease progression was 1.7 months. When patients discontinued for other reasons, median overall survival was not reached, compared with stopping for disease progression (P = .0008).
The researchers reported that among patients who discontinued for nonprogression reasons, 67% were alive after 1 year. Among CLL patients, 80% were alive after 1 year.
Among 20 patients who had a dose adherence of less than 80% in the first 8 weeks, the researchers found worse progression-free survival (P = .002) and overall survival (P = .021). Among CLL patients only, progression-free survival was significantly worse (P = .043) but overall survival was not (P = .816).
The study also included five patients who reduced their ibrutinib dose in the first 8 weeks – down to 280 mg in two patients, 140 mg in two patients, and 420 mg in one patient. Again, the researchers observed worse progression-free survival (P = .004) and overall survival (P = .014), compared with patients who maintained their dosing level.
Interrupting ibrutinib dosing had an impact on survival but not as much as discontinuation. Among 10 patients who interrupted therapy for more than a week and then restarted, progression-free survival was worse, compared with those who stayed on treatment continuously (P = .047), but overall survival was not significantly worse (P = .577).
“This would suggest that the ideal treatment strategy would be to recommend initiation of therapy at standard dosing and interruption as needed as directed in the [Food and Drug Administration] label,” the researchers wrote.
The study was funded by the National Cancer Institute and the Cadregari Endowment Fund. The researchers reported having no conflicts of interest.
SOURCE: Williams AM et al. Clin Lymphoma Myeloma Leuk. 2018 Oct 12. doi: 10.1016/j.clml.2018.10.005.