Marleen Kok, MD

“This is currently the largest data set with information on retreatment,” said formal study discussant Marleen Kok, MD, of the Netherlands Cancer Institute, Amsterdam, The Netherlands. She noted there was a partial response in 11% and stable disease in 60%. “Upon initial treatment, partial response was more pronounced, whereas on retreatment, most patients showed stable disease,” Dr. Kok said.

“Other small studies have also shown that a proportion of patients respond to retreatment, so it should be considered. However, in the study presented by Dr. Sheth and colleagues, all patients received anti–PD-L1 for 1 year only and response rates seem to be lower in patients with an early relapse after start of retreatment. This raises the question of whether 1 year of initial treatment is enough,” she said.

“In the largest retrospective study on retreatment so far, we see that the durability of response seems to vary. There are many open questions, and they need further study. It is probably safe to stop treatment, but this might be different for different tumor types. The original type of response might matter, 1 year of initial treatment might not be enough, and it is not clear whether the duration of treatment-free interval predicts success. There is still a lot of work to be done,” said Dr. Kok.

“It is a delicate balance whether to stop treatment or continue. For the individual patient, toxicity matters. Stopping treatment spares side effects and hospitalizations. Retreatment may also overstimulate the T cells, but on the other hand, continued treatment may improve outcomes,” she said. ■

DISCLOSURE: Dr. Kok has received institutional research funding from Bristol-Myers Squibb and Roche.