Evaluating pembrolizumab for patients with primary mediastinal large B-cell lymphoma that has come back or stopped responding to treatment

This study evaluated the safety and effectiveness of pembrolizumab (Keytruda) for patients with primary mediastinal large B-cell lymphoma (PMBCL) that has come back or stopped responding to treatment. This study concluded that pembrolizumab was safe and effective for these patients.

PMBCL is one rare and aggressive type of non-Hodgkin lymphoma (NHL). First-line treatment typically involves high-dose chemotherapy with or without radiation therapy. However, the cancer comes back (relapses) or becomes refractory (stops responding to treatment) in 10 – 20% of patients.

Targeted therapy is one treatment option for these patients. Pembrolizumab is a monoclonal antibody. This type of treatment helps the body’s immune system attack cancer cells. The safety and effectiveness of pembrolizumab for patients with PMBCL that has come back or stopped responding to treatment are under investigation.

This study analyzed data from 2 clinical trials. Study 1 had 21 patients and study 2 had 53 patients. On average, patients had an average of 2 to 9 previous lines of treatment. All patients received pembrolizumab for up to 2 years. Patients were followed for an average of 12.5 to 29.1 months.

In study 1, 48% of patients responded to treatment. 33% (7 patients) had no signs of cancer after treatment (complete response). 72% (13 patients) had tumor shrinkage. In study 2, 45% of patients responded to treatment. 13% (7 patients) had a complete response to treatment. 75% (30 patients) had tumor shrinkage. No patient who had a complete response experienced tumor growth or spread after treatment.

In study 1, patients survived for an average of 31.4 months. The average survival without tumor growth or spread was10.4 months. In study 2, patients survived for an average of 5.5 months without tumor growth or spread. 47% (study 1) and 38% (study 2) of patients were still alive a year later without tumor growth or spread. 65% (study 1) and 58% (study 2) of patients were still alive a year later.

Overall, 71% (study 1) and 57% (study 2) of patients had side effects. Serious side effects occurred in 24% (study 1) and 23% (study 2) of patients. The most common side effect was low white blood cell count that helps fight off infections (neutropenia). This occurred in 14% (3 patients) in s 1 study and 13% (7 patients) in study 2.

This study concluded that pembrolizumab was effective and well-tolerated in patients with PMBCL that has come back or stopped responding to treatment. The authors suggest that this treatment may be a good option for patients who experience relapse after or are not good candidates for a stem cell transplant.

This was a Phase 1 – 2 study with a small number of patients. Larger studies are needed to confirm the role of pembrolizumab in the treatment of patients with relapsed or refractory PMBCL.