Australian real world clinical experience of ibrutinib (Imbruvica) in patients with relapsed or refractory Chronic Lymphocytic Leukemia (CLL) shows that patient duration on therapy matches closely with the phase 3 trial findings.
Results from more than 1000 patients who accessed ibrutinib via the Named Patient Program (NPP) between 2014 and 2017 before it was listed on the PBS show that while 226 patients (22%) discontinued treatment by the end of the two years of the NPP, 85% remained on treatment for at least 12 months.
Analysis of the data that covered 783 patients with CLL and 232 with confirmed small lymphocytic lymphoma (SLL) showed that treatment duration was not significantly different from that seen in the RESONATE trial. In that trial, published in the NEJM in 2014, 391 patients with relapsed or refractory CLL or SLL were randomised to receive daily ibrutinib or the anti-CD20 antibody ofatumumab.
Ibrutinib significantly prolonged the duration of progression-free survival, with the median not reached at a median follow-up of 9.4 months, as compared with a median duration of progression-free survival of 8.1 months with ofatumumab.
In the Australian real world experience study, the median duration on treatment was not reached during the 36 months that the NPP period was open.
Predictors of time on treatment included age, with people in the 60-74 age group having significantly longer duration of treatment vs the reference group of patients 85 years and older. Patients whose CLL/SLL was diagnosed in the last five years showed a trend towards shorter duration of treatment.
The Australian study, led by Professors Con Tam of the Peter MacCallum Cancer Centre, Melbourne, and Stephen Mulligan from the Royal North Shore Hospital in Sydney, the patients had a median age of 72 years and 68% were male. During the first two years of the NPP program, more than half the patients entering the program had already undergone multiple treatments of patients, with 53% having had three or more lines of treatment. The proportion of patients having had three or more treatments decreased to 37% by 2017.
Presenting the findings at the European Haematology Association (EHA 2018) meeting in Stockholm, the study authors hypothesised that this reflected a high level of unmet need at the beginning of the NPP and an increasing degree of confidence in using a novel therapy in earlier lines as the program continued.
They cautioned that their findings for ibrutinib were based on physician reports and resupply of medication data, but said that nevertheless “these findings provide a real world estimate of time on treatment with ibrutinib that is similar to the time on treatment in the RESONATE trial.
Ibrutinib was listed on the PBS in 2017, at which time patients in the NPP were transitioned to PBS-subsidised therapy.
The analysis was conducted with support of Janssen, which markets ibrutinib.