Benefit still to be proven
In a media briefing held prior to his presentation, Dr. Machiels was asked how he could justify his conclusions about a benefit for adding pembrolizumab given that there was no difference between the treatment groups for the primary endpoint.
He said that when the investigators designed the trial 7 years ago, the CPS score for PD-L1 expression had not yet been developed, and that if it had been they might have designed the trial to explore the effect of the pembrolizumab chemoradiation combination according to CPS subgroups.
He also pointed to the numerically superior 2-year EFS and overall rates.
In the presidential symposium, James Larkin, MD, PhD, an invited discussant from the Royal Marsden Hospital, London, said that chemotherapy and anti–PD-1 therapies are known to offer benefit in advanced cancers despite the trial’s failure.
“There is a signal, particularly as we’ve seen in the high PD-L1 group,” he said, noting that the signal was consistent with that seen in the JAVELIN 100 study, which was also a negative trial. He cautioned against relying too heavily on the comparison, however, as JAVELIN 100 was conducted with avelumab, a PD-L1 inhibitor, whereas pembrolizumab is a PD-1 inhibitor.
“Could there be an issue here with treatment schedule? An example and a comparison might be the PACIFIC study in non–small cell lung cancer, which is a positive trial, where actually the checkpoint inhibit with durvalumab was given immediately after the chemoradiotherapy, leading to benefit, rather than being concurrent,” he said.
Dr. Larkin also questioned whether, as codiscussant Sherene Loi, MD, PhD, from the Peter MacCallum Cancer Center, Melbourne, suggested radiotherapy to lymph nodes might alter the immune response to checkpoint inhibitors.
“Clearly radiotherapy is the central component of treatment in this setting, so it would be quite difficult to scale too much on that, but the question is: ‘Could it be modified?’ For example, just to irradiate the primary tumor and involved lymph nodes and potentially spare noninvolved lymph nodes,” he said.
The KEYNOTE-412 study was funded by Merck Sharp & Dohme. Dr. Machiels reported uncompensated consulting to the company. Dr. Larkin reported consulting for and receiving honoraria from Merck and others. Dr. Loi reported uncompensated advisory board activity for Merck and others.
