by Dr. C.H. Weaver M.D. updated 4/2019
Merck released a press statement in April 2019 that their Phase 3 trial evaluating Keytruda (pembrolizumab) as a first-line treatment for gastric cancer failed to show improvement when compared with chemotherapy. Studies looking at Keytruda as a second-line treatment for gastric cancer also failed to show a survival benefit, though the Food and Drug Administration has approved Keytruda for patients with advanced gastric cancer and some patients may benefit from its use.(1)
Keytruda initially appeared promising in patients with pretreated metastatic gastric cancer, according to the results of the KEYNOTE-059 trial presented at the European Society for Medical Oncology (ESMO) 2017 Congress in Madrid.(2)
Stomach cancer (gastric cancer), is the third leading cause of cancer-related deaths worldwide. Overall, the 5-year survival rate for patients with gastric cancer is 30.4%. However, once the cancer has spread from the stomach to distant sites in the body, the 5-year survival rate drops to 5%, indicating the need for novel treatment options. Very few new drugs have been approved for this disease in the past decade. The phase II KEYNOTE-059 is one of the largest studies to investigate immunotherapy in recurrent or metastatic gastric cancer.
Keytruda is a monoclonal antibody that helps to restore the body’s immune system in fighting cancer. It creates its anti-cancer effects by blocking a specific protein used by cancer cells called the programmed death-ligand 1 (PD-L1), to escape an attack by the immune system. Once PD-L1 is blocked, cells of the immune system are able to identify cancer cells as a threat, and initiate an attack to destroy the cancer.
The current study included three groups: 1) 259 patients with metastatic gastric cancer who were treated with keytruda alone, after pretreatment with two or more lines of chemotherapy; 2) 25 patients with newly diagnosed metastatic gastric cancer who received a combination of keytruda and chemotherapy; 3) 31 patients with newly diagnosed metastatic gastric cancer who received keytruda alone.
The investigators reported an overall objective response rate of 12% with keytruda alone in the pretreated patients and the patients who expressed PD-L1 were more likely to respond than those who did not, with objective response rates of 16%.
In patients with newly diagnosed metastatic cancer, both the combination therapy and keytruda alone were safe and showed some promising activity. These study results are consistent with those reported for Opdivo (nivulomab) another PD-1 inhibitor reported earlier this year and support an emerging role of immunotherapy for selected patients with gastric cancer.
- Abstract LBA28_PR ‘KEYNOTE-059 Update: Efficacy and Safety of Pembrolizumab Alone or in Combination With Chemotherapy in Patients With Advanced Gastric or Gastroesophageal (G/GEJ) cancer.
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