Combined Immunotherapy, Thoracic RT Carries Moderate Toxicity in Lung Cancer

A study of the combination of radiation therapy and immune checkpoint inhibitors (ICPIs) for the treatment of advanced lung cancer found a modest risk of side effects. The risk of pneumonitis appeared highest when thoracic radiation therapy (TRT) was delivered after ICPI therapy.

“The use of immune checkpoint inhibitors has become increasingly common in the management of advanced lung cancer,” said Kamran Ahmed, MD, of Moffitt Cancer Center in Tampa, Florida, during a press briefing at the 2017 Multidisciplinary Thoracic Cancers Symposium, held March 16–18 in San Francisco. “There is preclinical rationale to combine the use of RT with ICPI to enhance the efficacy of these agents,” but little was known about the potential toxicity of the combination.

He presented results of a retrospective study of 29 patients who received TRT within 6 months of ICPI therapy with either anti–PD-1 or anti–PD-L1 therapy alone or in combination with an anti–CTLA-4 agent. Most of the cohort (59%) received single-agent therapy. The median age of patients was 64 years, and 79% had non–small-cell lung cancer (NSCLC). About half the patients (52%) received the therapies concurrently, while 14 patients received RT between 2 weeks and 5.5 months before ICPI initiation.

Three patients (10%) experienced severe possibly treatment-related pneumonitis; one grade 5 toxicity occurred 2 weeks after RT, while the other two occurred 2 and 4 months after RT, respectively. Two additional patients experienced pneumonitis (one grade 2 and one grade 3) attributable to ICPIs alone, and went on to receive TRT without further toxicity.

The median overall survival in the cohort was 9.2 months, and the median progression-free survival was 3.8 months.

“Treatment with ICPIs and thoracic radiation therapy carried a modest risk of side effects,” Ahmed said. “Our study indicates the risk of TRT/ICPI-related pneumonitis may be highest when TRT is delivered after ICPI therapy.” He added that further studies should continue to assess the synergistic effects of these therapies, as well as any further toxicities that may emerge.

Ravi Salgia, MD, PhD, of the City of Hope Cancer Center in Duarte, California, was the moderator for the press briefing. The study, he said, “shows potential for the tolerability and efficacy of this emerging type of targeted combination therapy for advanced disease.”