Dr Lee on the Optimal Patient Population to Receive Proton Therapy for Advanced NSCLC

“Proton therapy is [ideal to use in] a special subset of patients [who] are challenging to deliver that radiation dose to, based on anatomy, location of the tumor, [or tumor] size.”

Percy Lee, MD, vice chair of Clinical Research in the Department of Radiation Oncology, medical director of Orange County & Coastal Region Radiation Oncology, and a professor in the Department of Radiation Oncology at City of Hope, discussed the differentiated application of radiation modalities, the increasing complexity of re-irradiation, and the strategic use of stereotactic ablative radiotherapy (SABR) for patients with non–small cell lung cancer (NSCLC).

Regarding the selection of fundamental radiation modalities, Lee noted that most patients with NSCLC benefit from photon therapy alone. Proton therapy, conversely, is generally considered ideal for a special subset of patients, he said. This specialized use is dictated when radiation dose delivery proves challenging due to anatomical constraints, the specific location of the tumor, or the size of the disease, he reported. The use of proton therapy is ultimately a case-by-case determination, suggesting that although it is not necessary for every patient, certain patients could benefit from its application, he emphasized.

The practice of re-irradiation is complicated, yet its prevalence is increasing, according to Lee. This rise in reirradiation rates is attributed to patients experiencing better outcomes with modern systemic therapy, he stated. A critical component of successful reirradiation is timing, he added. Time intervals of at least 1 year between the last course of radiation therapy are typically favored, as this minimizes the risk of toxicity, limits the radiation dose to healthy tissue, and maintains constraints believed to be relatively safe, he explained. Furthermore, the ability to administer chemotherapy concurrently with a definitive second course of radiation therapy appears to contribute to better patient outcomes, he reported.

SABR is defined as localized high-dose radiation for patients with a limited size of disease, Lee continued. Currently, patient eligibility for SABR often relies on the number of lesions, with 3 to 4 lesions considered optimal, he said. The clinical imperative is to accurately distinguish between patients presenting with aggressive vs indolent cancer, thereby allowing SABR to target and control specific sites of disease, he reported. Leveraging SABR in this manner in the metastatic setting enables patients to achieve a chemotherapy-free or systemic therapy–free interval, or allows for the strategic delay of subsequent lines of systemic therapy, he concluded.