ASTRO 2019: How radiation after immunotherapy helps some NSCLC patients

Radiation boosts the immune system of patients with metastatic non-small-cell lung cancer (NSCLC) after they stop responding to immunotherapy, according to findings presented at the 2019 annual meeting of the American Society for Radiation Oncology (ASTRO).

“This study provides one more important piece of data that indicates that, for some patients, the immune system can be a really powerful tool to combat metastatic lung cancer,” lead author Allison M. Campbell, MD, PhD, a resident at the Yale Cancer Center, said in a prepared statement. “It points us in the direction of places to look for biomarkers that might predict which patients would best respond to this type of therapy.”

Campbell and colleagues examined data from 56 patients with NSCLC with at least two tumors. Six patients had already received immunotherapy and stereotactic body radiotherapy (SBRT), and the other 50 patients had not been treated with immunotherapy. Of those 50 patients, 16 were treated with SBRT after being treated with pembrolizumab.

Overall, 21 patients completed both treatment methods and lived an average of five months longer without further disease progression. For two patients, tumors outside the area treated by SBRT shrank by at least 30%. The tumors stabilized in another 10 patients.

The researchers also found that T cells played a key role in determining how a patient’s immune system might respond to SBRT. In patients who responded well to the treatment, some CD8 T cells “looked more excited.” In patients who did not respond well to the treatment, on the other hand, “a population of CD4 T cells with inhibitory markers” was present.

The next step, according to Campbell, is to validate her team’s findings with more research.

“We are starting to see that the combination of immunotherapy and radiation is safe and there are some hints that for certain patients, radiation might be an important option when immunotherapy no longer curbs disease progression,” she said in the statement. “Our study lays the groundwork for a phase III randomized trial, which is the gold standard for changing guidelines and clinical practice.”

The 2019 ASTRO annual meeting is Sept. 15-18 in Chicago.