Intermediate Results of Prospective Observational Study: The 2-year Experience of Ibrutinib Therapy in Relapsed/Refractory Mantle Cell Lymphoma in Clinical Practice

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Aim. To assess efficacy and toxicity of ibrutinib monotherapy in patients with relapsed/refractory mantle cell lymphoma (MCL). Materials & Methods. In this group of patients ibrutinib has been used since April 2016. Ibrutinib administration criteria were the age > 18 years and the confirmed MCL diagnosis with nuclear hyperexpression of cyclin D1 and t(11;14)(q13;q32) translocation. Poor physical status, pancytopenia, infectious complications (except for life-threatening conditions), blastoid variant, and the number of previous treatment lines were not regarded as contraindications to ibrutinib therapy. Oral ibrutinib was administered once a day at a dose of 560 mg before progression and until intolerable toxicity was observed. Results. From April 20, 2016 to April 6, 2018 ibrutinib therapy was provided to 42 patients with relapsed/refractory MCL. The median age was 69 years (range 40–81); 64 % of patients were men; ECOG > 2 was registered in 14 % of patients; 38 % of patients had blastoid variant; the median number of previous treatment lines was 2 (range 1–11). The overall response rate was 85 % (35 % were in complete remission); 57 % (24/42) of patients remain on ibrutinib treatment for the period of 4–667 days. The median event-free survival (EFS) was 365 days (95% confidence interval was 31–698 days). The median overall survival was not achieved. In blastoid variant the median EFS was 92 days, in the alternative group the median was not achieved and EFS was 76 % for 12 months (p < 0.001). In the majority of cases ibrutinib was well tolerated by patients. The most common complications were myalgia and muscle cramps (57 % cases), diarrhea (46 %, and grade 3 in 5 % cases), hemorrhagic complications (63 %, all of them of grade 1–2), and arrhythmia (7 %). Infectious complications were reported in 31 % of patients. In one case the start of ibrutinib treatment appeared to be problematic due to neutropenia of grade 4. Relative dose intensity was > 98 % (range 91.6–100 %). In 10 (24 %) patients ibrutinib treatment had to be adjusted (dose reduction or treatment interruption) due to toxicity and planned surgeries. None of ibrutinib recipients had to completely discontinue ibrutinib therapy due to complications. Conclusion. These data on the use of ibrutinib in actual clinical practice are comparable with the results of international multicenter studies (PCYC-1104, SPARK, and RAY). Reduced toxicity profile and rather high speed of antitumor response allow for ibrutinib administration in cases of poor physical status, low blood count, and even infectious complications. However, some adverse effects are manifested not earlier than after 6-month treatment, which calls for continuous monitoring, especially when preparing for surgeries.

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