However, patients still fared poorly on average since overall survival remained low and didn’t change significantly.
While not conclusive, the new research – released at European Lung Cancer Congress 2023 – offers early insight into the best timing for the experimental combination treatment, study coauthor Yanyan Lou, MD, PhD, an oncologist at Mayo Clinic in Jacksonville, Fla., said in an interview.
The wide availability of radiation therapy could also allow the therapy to be administered even in regions with poor access to sophisticated medical care, she said. “Radiation is a very feasible approach that pretty much everybody in your community can get.”
Radiotherapy is typically not added to immunotherapy in patients with non–small cell lung cancer. But “there has been recent interest in the combination: Would tumor necrosis from radiation enhance the immunogenicity of the tumor and thus enhance the effect of immunotherapy?” oncologist Toby Campbell, MD, of University of Wisconsin–Madison, said in an interview.
Research has indeed suggested that the treatments may have a synergistic effect, he said, and it’s clear that “strategies to try and increase immunogenicity are an important area to investigate.”
But he cautioned that “we have a long way to go to understanding how immunogenicity works and how the gut microbiome, tumor, immunotherapy, and the immune system interact with one another.”
For the new study, researchers retrospectively analyzed cases of 225 patients with metastatic non–small cell lung cancer (male = 56%, median age = 68, 79% adenocarcinoma) who were treated with immunotherapy at Mayo Clinic–Jacksonville from 2011 to 2022. The study excluded those who received targeted therapy or prior concurrent chemoradiotherapy and durvalumab.
The most common metastases were bone and central nervous system types (41% and 25%, respectively). Fifty-six percent of patients received radiotherapy before or during immunotherapy. Another 27% never received radiotherapy, and 17% received it after immunotherapy was discontinued.
Common types of immunotherapy included pembrolizumab (78%), nivolumab (14%), and atezolizumab (12%).
Overall, the researchers found no statistically significant differences in various outcomes between patients who received radiotherapy before or during immunotherapy compared with those who didn’t get radiotherapy (progression-free survival: 5.9 vs. 5.5 months, P = .66; overall survival: 16.9 vs. 13.1 months, P = .84; immune-related adverse events: 26.2% vs. 34.4%, P = .24).
However, the researchers found that progression-free survival was significantly higher in one group: Those who received radiotherapy 1-12 months before immunotherapy vs. those who received it less than 1 month before (12.6 vs. 4.2 months, hazard ratio [HR], 0.46, 95% confidence interval [CI], 0.26-0.83, P = .005,) and those who never received radiotherapy (12.6 vs. 5.5 months, HR, 0.56, 95% CI, 0.36-0.89, P = .0197).
There wasn’t a statistically significant difference in overall survival.
The small number of subjects and the variation in treatment protocols may have prevented the study from revealing a survival benefit, Dr. Lou said.
As for adverse effects, she said a preliminary analysis didn’t turn up any.
It’s not clear why a 1- to 12-month gap between radiotherapy and immunotherapy may be most effective, she said. Moving forward, “we need validate this in a large cohort,” she noted.
In regard to cost, immunotherapy is notoriously expensive. Pembrolizumab, for example, has a list price of $10,897 per 200-mg dose given every 3 weeks, and patients may take the drug for a year or two.
Dr. Campbell, who didn’t take part in the new study, said it suggests that research into radiation-immunotherapy combination treatment may be worthwhile.
No funding was reported. The study authors and Dr. Campbell reported no disclosures.