Conference Coverage

Ibrutinib-rituximab induction yields ‘unprecedented’ responses in MCL



– In younger patients with previously untreated mantle cell lymphoma, the chemotherapy-free combination of ibrutinib and rituximab followed by a short course of chemotherapy was associated with an “unprecedented” 3-year progression-free survival rate, investigators in the phase 2 WINDOW-1 trial reported.

Michael Wang, MD, University of Texas MD Anderson Cancer Center in Houston Neil Osterweil/MDedge News

Dr. Michael Wang

Among 50 patients aged 65 years and younger who received ibrutinib and rituximab until they achieved a complete or partial response, followed by four cycles of chemotherapy with rituximab plus hyper-CVAD (cyclophosphamide, vincristine, doxorubicin and dexamethasone) and rituximab plus methotrexate, the 3-year progression-free survival (PFS) rate was 88%, said Michael Wang, MD, from the University of Texas MD Anderson Cancer Center in Houston.

Additionally, for patients with the low-risk features, the 3-year PFS rate was 90%.

“Chemo-free ibrutinib-rituximab induced unprecedented – unprecedented – efficacy before chemo consolidation,” he said at the International Conference on Malignant Lymphoma.

Dr. Wang presented data from an interim analysis of the investigator-initiated single-center trial. Fifty patients aged 65 years or younger with untreated mantle cell lymphoma (MCL), good performance status, and good organ function were enrolled.

The patients were treated with ibrutinib and rituximab for two cycles and then evaluated for response with PET-CT scan, bone marrow biopsy, and for some patients, esophagogastroduodenoscopy (EGD) and colonoscopy with random biopsies.

In the induction phase, patients received ibrutinib daily on days 1-28 and rituximab intravenously over 6-8 hours on days 1, 8, 15, and 22 of cycle 1, and then over 4 hours on day 1 of cycles 3-12. The treatment was repeated every 28 days for up to 12 cycles in the absence of disease progression or unacceptable toxicity, or until patients achieved a complete response.

In the consolidation phase, patients received rituximab IV over 6 hours on day 1; oral or IV dexamethasone on days 1-4; cyclophosphamide IV over 3 hours twice daily on days 2-4; doxorubicin IV over 15-30 minutes on day 5; and vincristine IV over 15-30 minutes on day 5 of cycles one, three, five, and seven. Patients also received rituximab IV over 6 hours on day 1; methotrexate IV over 24 hours on day 2; and cytarabine IV over 2 hours twice daily on days 3 and 4 of cycles two, four, six, and eight. Treatments were repeated every 28 days for up to eight cycles in the absence of disease progression or unacceptable toxicity.

Patients who had a complete response (CR) after two cycles of induction and those who had disease progression on induction went on to consolidation. Patients with partial responses (PR) to induction continued on ibrutinib/rituximab until either the loss of a PR or best response for up to 12 cycles, with those who achieved a CR then moving on to consolidation.

Patients who had a CR after induction received four cycles of R-hyperCVAD, no subsequent stem cell transplant, and no maintenance therapy. Patients who had a PR after induction received two cycles of R-hyperCVAD, were reassessed, and then continued on R-hyperCVAD until CR or for up to eight total cycles.

Patients with either stable disease or progression during R-hyperCVAD were taken off the study.

Of the 50 patients enrolled, all 50 were evaluable for part A (induction), and 48 were evaluable after induction and consolidation (two patients withdrew for personal reasons).

After a median follow-up of 36 months, the overall response rate (ORR) following induction was 100%, consisting of 46 CRs (92%) and four PRs (8%).

In an intention-to-treat analysis (including the two patients who withdrew), the ORR was 96%, consisting of CRs in 47 patients (94%) and a PR in 1 patient (2%).

Neither the median PFS nor median overall survival had been reached at the time of data cutoff, and no patients have died.

Of the 50 enrolled patients, four experienced disease progression after 17, 24, 34, and 35 months of treatment. The patients with disease progression included one with Ki-67 of less than 30%, and three with KI-67 of 30% or greater.

Grade 3-4 toxicities during induction including myelosuppression in 4%; fatigue, myalgia, and rashes in 8% each; and oral mucositis in 4%.

Dr. Wang said that future studies on minimal residual disease and clonal evolution are ongoing, and that data on more patients will be presented at the next annual meeting of the American Society of Hematology, scheduled for December 2019.

He also noted that the WINDOW-2 trial, in which ibrutinib and rituximab are followed by veneotclax and hyper-CVAD chemotherapy in patients with newly diagnosed MCL, is open and rapidly enrolling patients.

The study is supported by the National Cancer Institute. Dr. Wang reported financial relationships with Janssen, Pharmacyclics, and other companies.

SOURCE: Wang M et al. ICML-15, Abstract 12.

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