Ibrutinib ‘treatment of choice’ in rel/ref MCL

Dr Rule also pointed out that the improvement in PFS with ibrutinib was consistent across subgroups (ie, older age, risk score, tumor bulk, refractory disease). The only exception was patients with blastoid histology, but this was a very small group.

Secondary endpoints

The median OS was not reached in the ibrutinib arm but was 21.3 months in the temsirolimus arm.

This difference was not statistically significant, but Dr Rule noted that the trial was not powered for OS, and the analysis is confounded by the crossover. Twenty-three percent of patients in the temsirolimus arm ultimately received ibrutinib.

The overall response rate (ORR) was 71.9% in the ibrutinib arm and 40.4% in the temsirolimus arm (P<0.0001), according to the independent review committee. The complete response rates were 18.7% (n=26) and 1.4% (n=2), respectively.

The median duration of response was not reached with ibrutinib but was 7 months for temsirolimus. The median time to next treatment was not reached with ibrutinib, but it was 11.6 months in the temsirolimus arm (P<0.0001).

And the median duration of study treatment was 14.4 months in the ibrutinib arm and 3 months in the temsirolimus arm.

Timing counts

Dr Rule also presented response and PFS data according to the number of prior therapies patients received.

He noted that patients were more likely to respond to temsirolimus if they had received fewer prior therapies, but this was not the case with ibrutinib. Ibrutinib produced consistent ORRs regardless of when it was given.

In the ibrutinib arm, the ORR was 71.9% for patients who had received 1 prior line of therapy, 68.4% for those who received 2 prior therapies, and 75% for those who received 3 prior therapies. In the temsirolimus arm, the ORRs were 48%, 39.5%, and 33.3%, respectively.

Conversely, patients had a greater PFS benefit if they received ibrutinib earlier in their treatment course, but this was not true for temsirolimus.

At the median follow-up of 20 months, PFS was more than 60% for ibrutinib-treated patients who had received 1 prior line of therapy and less than 30% for ibrutinib-treated patients who received 2 or more prior lines of therapy. PFS was less than 15% for patients in the temsirolimus arm, regardless of their number of prior therapies.

“So that’s perhaps the first hint that, if we’re going to be using [ibrutinib], we should be using it earlier on,” Dr Rule said. “And I also suspect that, with further follow-up with this study, if this holds up, there will be, indeed, a survival benefit observed.”

Safety

“Despite patients on the ibrutinib arm being exposed to drug more than 4 times longer than those with temsirolimus, the frequency of most cumulative adverse events was lower in the ibrutinib arm,” Dr Rule said.

Still, he noted that most patients had some adverse events. And grade 3 or higher adverse events were reported in 67.6% of patients on ibrutinib and 87.1% of patients on temsirolimus.

Grade 3 or higher AEs included atrial fibrillation (AFib) and major bleeding. AFib occurred in 4.3% of patients in the ibrutinib arm and 1.4% in the temsirolimus arm. Major bleeding occurred in 10.1% and 6.5%, respectively.

Five of the 6 patients with AFib in the ibrutinib arm and all 3 patients who developed AFib in the temsirolimus arm had risk factors for AFib prior to treatment. None of these patients discontinued treatment due to AFib.

Dr Rule said there was no evidence to suggest that either drug increases the risk of second primary malignancies, although 3.6% of patients in the ibrutinib arm and 2.9% in the temsirolimus arm were diagnosed with second primary malignancies (mostly non-melanoma skin cancers).