"Incorporating radiotherapy into the treatment of patients with oligometastatic or metastatic non–small cell lung cancer (NSCLC) is standard practice, but its optimal placement in the paradigm is less clear," said James Urbanic, MD.

To determine whether it should be used up front or in later lines of treatment, researchers are exploring how the addition of immunotherapy changes the role of radiation. Advances in targeted therapies, such as osimertinib (Tagrisso) and alectinib (Alecensa), are also likely to impact radiation’s role in treatment. 

Better blood-brain penetration with these agents enables radiation oncologists to hold off on treating brain metastases, resulting in less incidence of whole-brain radiotherapy and treatment-emergent adverse events.

Advances in radiation techniques and technology are also refining the use of radiation in NSCLC. “The speed of delivery and the complexity that we can deliver the radiation to the patient from different angles are changing as both the software and hardware improve,” explained Urbanic.

In an interview during the 2018 OncLive State of the Science Summit on Non–Small Cell Lung Cancer, Urbanic, associate professor of Radiation Medicine and Applied Sciences, University of California, San Diego, discussed the evolving role of radiotherapy in patients with oligometastatic and metastatic NSCLC.

An overview

"I spoke about when we should use radiation treatment in metastatic NSCLC, particularly in the setting in which a patient might have 1 to 3 relatively small metastases. Historically, chemotherapy has had modest effectiveness," added Urbanic.

"Initially, surgeons pioneered this idea of taking out a few small metastatic sites. As radiation treatment has gotten better over the past number of years, we have gotten better at picking off small areas of disease with very high-dose radiation treatments," said Urbanic.

The evolution of techniques

Radiation techniques are based on stereotactic radiosurgery, given in either 1 treatment or a short course of 1 to 5 treatments. That means it is trying to give a very high dose to the tumor itself in a very steep, rapid-dose gradient, or fall off from the high-dose area to the low-dose area.

"You're treating the tumor itself with the lethal dose of radiation to those cells. Those techniques are being further refined. There are some limitations to how much more you can refine x-rays," noted Urbanic.

Tolerability with radiation therapy

"It is all location dependent. There are many patients we can treat for a very small target; those patients have a very limited risk. As we start treating more sites, larger tumors, and disease in parts of the body that don't have a lot of redundancy, the risk goes up," added Urbanic.

"For example, if you treat metastasis in the brain stem, that patient is going to have a fairly high risk of toxicity. If you treat a tumor in the main stem bronchus, you have a risk of causing injury to that part of the lung; that has a high risk of serious toxicity. For the most part, risks are fairly limited for many small and isolated tumors," said Urbanic.