New treatments are becoming available for one of the most common and deadly cancers, lung cancer. More than 28,000 Canadians were diagnosed with lung cancer in 2016 and 21,000 died. The lung cancer survival rate 5 years after diagnosis is only 17%, one of the lowest of all cancers.
In October 2016, the US Food and Drug Administration (FDA) approved the first checkpoint inhibitor drug for first-line treatment of lung cancer, a major win for immunotherapy.
New immunotherapy drug approved for lung cancer treatment
First-line treatment means that a drug or therapy can be used as soon as a cancer is diagnosed. This treatment is well understood and has a proven track record. Second-line treatments, which are newer and not as well understood, can only be used if the first-line therapy has failed. Given their experimental nature, many drugs in clinical trials are second-line treatments.
The FDA approved the drug pembrolizumab, more commonly known as Keytruda, for first-line treatment. It was approved for the treatment of metastatic non-small cell lung cancer (NSCLC) that specifically has high amounts of a surface marker called PD-L1. This decision also approved the use of Keytruda as a second-line treatment for all NSCLC patients with tumours expressing the PD-L1 marker.
Clinical trials show Keytruda is an effective lung cancer treatment
Immune cells have a marker on their surface called PD-1, which can bind with its corresponding marker on the surface of cancer cells, PD-L1, and turn off an immune response against the cancer cells. Keytruda is a PD-1 inhibitor, which means it blocks the PD-1 marker on immune cells, preventing them from interacting with PD-L1 on cancer cells and allowing the immune system to recognize and attack the cancer cells.
The FDA’s approval of Keytruda was based on the results of 2 key positive clinical trials. Patients treated with Keytruda lived longer, without their disease spreading or growing, compared with those patients treated with chemotherapy, the traditional standard of care.
In December 2016, Japan also approved Keytruda for both first- and second-line treatment for patients with metastatic NSCLC that have the PD-L1 marker.
As of March 2016, Keytruda has only been approved as a second-line treatment for NSCLC in Canada. Keytruda can be used to treat patients with metastatic NSCLC whose tumours have the PD-L1 marker and whose disease has progressed after chemotherapy or other therapies. Before further approvals can be made, Health Canada is waiting for more clinical trial results.
Questions still remain about immunotherapy drugs
Late last year, researchers announced more exciting news for treating NSCLC with checkpoint inhibitors. Researchers conducting a phase 3 clinical trial found that patients with advanced NSCLC survived 4 months longer with fewer side effects while taking atezolizumab (Tecentriq), a new checkpoint inhibitor targeting PD-L1, compared with patients given chemotherapy.
Tecentriq, like Keytruda, works on the PD-1 and PD-L1 pathway. However, it blocks PD-L1 on the surface of the cancer cells instead of PD-1 on immune cells. The study is the first phase 3 trial of a PD-L1 inhibitor drug, and it showed longer patient survival than trials of PD-1 inhibitors.
Immunotherapy with checkpoint inhibitors that target the PD-1 and PD-L1 pathway have been a major therapeutic breakthrough. Treatment with these drugs can improve the survival of NSCLC patients who have not responded to traditional therapies.
Yet for this exciting treatment to gain more approvals for first-line treatment, several areas still need further study. For example, researchers need to determine the best schedule for providing these checkpoint inhibitor treatments. They also need to determine the length of treatment, an important factor since these drugs are very expensive. Also, researchers are looking to see if combinations of different immunotherapies might work more effectively in treating NSCLC and other cancers.
Katherine Wright, PhD