A new treatment for a rare B-cell malignancy provided an objective response rate of 41% in a clinical trial, published in Blood (published online May 10, 2017; doi:10.1182/blood-2016-12-758383).
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Primary mediastinal B cell lymphoma (PMBCL) is a subtype of diffuse large B cell lymphoma that is very difficult to eradicate in the relapsed or refractory setting and offers a poor prognosis. Prior research has shown that pembrolizumab, a PD-1 inhibitor, provides better survival outcomes than salvage therapy in patients with relapsed or refractory PMBCL. However, limited research exists on the safety and efficacy of this therapy in heavily pretreated patients with relapsed or refractory PMBCL.
A group of multinational researchers led by Pier Luigi Zinzani, MD, PhD, Institute of Hematology, University of Bologna (Italy), conducted a study to test pembrolizumab in heavily pretreated patients with relapsed or refractory PMBCL. A total of 11 of patients received pembrolizumab (10 mg/kg) every 2 weeks intravenously for up to 2 years (or if unacceptable toxicity or disease progression occurred). After a protocol amendment, 8 of the patients received a fixed dose (200 mg/kg) every 3 weeks. Pembrolizumab was the median fourth line of therapy among all patients. Median duration of follow-up was 11.3 months.
Results of the study showed that 41% of patients demonstrated an objective response rate, 2 of whom had a complete response and 5 of whom had a partial response. Thirty-five percent of patients showed stable disease. Authors acknowledged that the overall response rate of 41% was significantly higher than those reported in previous studies, where overall response rate ranged from 0% to 25%.
Median duration of response and overall survival was not reached.
The most common adverse events as a result of pembrolizumab treatment were hypothyroidism, diarrhea, nausea, fatigue, pyrexia, and decreased appetite. Grade 3 neutropenia was reported in only 1 patient. Immune-related adverse events included grade 2 aggravated diarrhea and grade 2 radiation pneumonitis. No patient discontinued treatment and there were no reported treatment-related deaths.
Authors of the study concluded that “These results in heavily pretreated [relapsed or refractory PMBCL] patients demonstrated that PD-1 blockade with pembrolizumab has a manageable safety profile and promising antitumor activity.” — Zachary Bessette
