Keytruda and Other Checkpoint Inhibitors for Treatment of Esophageal Cancer
by C.H. Weaver M.D. updated 6/2020
The checkpoint inhibitor Keytruda (pembrolizumab) was initially reported to produce an overall response rate of 30% in patients with PD-L1–positive, advanced esophageal cancer.(1) Additional results from the Keynote 181 clinical trial confirmed that Keytruda reduces the risk of death by 31% compared to treatment with chemotherapy in patients with esophageal or esophagogastric junction cancer or adenocarcinoma of the esophagus who progressed after initial standard chemotherapy.
The FDA approved Keytruda for the treatment of patients with recurrent, locally advanced or metastatic, squamous cell carcinoma of the esophagus (ESCC) and tumors expressing PD-L1 (determined by an FDA-approved test) that progressed after ≥1 lines of systemic therapy in July 2019.
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.
About Esophageal Cancer
The esophagus is a muscular tube that food and liquids pass through on their on their way to the stomach. Each year in the United States, more than 17,000 people are diagnosed with cancer of the esophagus and more than 15,000 die of the disease. (2) Patients with advanced esophageal squamous cell carcinoma have a poor prognosis and few treatment options after first-line therapy – new treatments are sorely needed.
Although many people with esophageal cancer are diagnosed with advanced disease, treatment has slowly improved, and survival rates are getting better. During the 1960s and 1970s, only about 5% of patients survived 5 years after being diagnosed. Now, about 20% of patients survive at least 5 years. The high death rate associated with esophageal cancer is largely attributed to the fact that the disease is often diagnosed once it has already become advanced, and few good treatment options exist. There is a very substantial unmet need for effective and well-tolerated treatments for patients with advanced esophageal carcinoma.
Keytruda Treatment of Esophageal Cancer
The KEYNOTE-028 clinical trial initially evaluated Keytruda in patients with 20 different types of PD-L1–positive advanced solid tumors and reported an overall response to treatment of 30% in esophageal cancer. For patients with squamous cell carcinoma the rate was 28%, and for those with adenocarcinoma it was 40%. (1)
In order to confirm the encouraging results with Keytruda in Keynote-028 the phase 3 Keynote-181 clinical trial was designed to assess Keytruda monotherapy in the second-line treatment of advanced or metastatic esophageal or esophagogastric junction carcinoma.
Keynote 181 directly compared Keytruda to chemotherapy in ~ 600 individuals with esophageal cancer that had recurred after initial chemotherapy treatment. Patients were treated with Keytruda or a the investigator’s choice of Taxol (paclitaxel) Taxotere (docetaxel). or Camptosar (irinotecan). The PD-L1 IHC 22C3 pharmDx kit was used to determine PD-L1 status.
Among patients whose cancer expressed PD-L1 CPS ≥10 the average survival was 10.3 months with Keytruda compared to 6.7 months in the control arm.(4)
The KEYNOTE‑180 clinical trial included 121 patients with locally advanced or metastatic esophageal cancer progressing on or after ≥2 previous systemic therapies. Twenty percent of patients with PD-L1 CPS ≥10 responded to treatment and responses lasted from 4.2 to over 25 months. Over half of these patients responded to treatment over a year.(4)
Camrelizumab Improves Survival Over Chemo in Esophageal Cancer
The results of a phase 3 clinical trial suggest that second-line camrelizumab treatment can significantly improves overall survival in patients with advanced or metastatic esophageal squamous cell carcinoma. Camrelizumab is another “checkpoint inhibitor” monoclonal antibody directed against the cell surface receptor programmed death-1 (PD-1, PCD-1,). Camrelizumab binds to and blocks the binding of PD-1, expressed on immune cells and prevents the activation of PD-1 and its downstream signaling pathways restoring immune function of cytotoxic T lymphocytes (CTLs) and cell-mediated immune responses against cancer cells.
Between May, 2017, and July, 2018, a total of 457 patients with advanced or metastatic esophageal squamous cell carcinoma who had failed prior treatment were enrolled in a study performed in 43 hospitals across China. Patients were treated with either camrelizumab or a Taxotere (docetaxel) irinotecan chemotherapy regimen and directly compared.
Average survival duration was 8.3 months for camrelizumab treated patients compared to 6.2 months for those treated with chemotherapy. The most frequently documented sided effects were anemia and diarrhea. (5)
- Doi T, et al “Safety and antitumor activity of the anti–programmed death-1 antibody pembrolizumab in patients with advanced esophageal carcinoma” J Clin Oncol 2018; DOI: 10.1200/JCO.2017. 74.9846.
- American Cancer Society. Cancer Facts and Figures 2015. Available here.
- Merck’s Keytruda improves overall survival in phase 3 esophageal cancer trial
- US Food and Drug Administration. FDA approves pembrolizumab for advanced esophageal squamous cell cancer. Updated July 31, 2019. Accessed July 31, 2019.
- Lancet Oncol. 2020 May 13. Epub ahead of print