Conference Coverage

PACIFIC: Patterns of lung cancer progression suggest role for local ablative therapy



Most patients with stage III non–small cell lung cancer (NSCLC) who have distant progression on standard therapy typically have one or two new lesions, often in the same organ, which suggests a role for local ablative therapy, according to investigators.

Dr. Andreas Rimner, of the Memorial Sloan Kettering Cancer Center in New York,

Dr. Andreas Rimner

This conclusion was drawn from an exploratory analysis of the phase 3 PACIFIC trial, which previously showed that durvalumab prolonged survival among patients with NSCLC who did not progress after chemoradiotherapy, which turned the trial protocol into a new standard of care.

At the annual meeting of the American Society for Radiation Oncology, coauthor Andreas Rimner, MD, of the Memorial Sloan Kettering Cancer Center in New York presented findings.

“There were always questions regarding detailed patterns of failure and disease progression in [the PACIFIC] trial,” Dr. Rimner said. “This study ... focuses on these patterns of failure, including the type of first progression in the patients on the PACIFIC trial.”

During the trial, 713 patients with NSCLC were randomized in a 2:1 ratio to receive either durvalumab or placebo. After a median follow-up of 25.2 months, the superiority of durvalumab was clear, with a lower rate of progression (45.4% vs. 64.6%).

But the present analysis dug deeper into this finding by dividing patients into three groups based on site or sites of first progression: local (intrathoracic) progression only, distant (extrathoracic) progression only, or simultaneously local and distant progression. Scans were reviewed by an independent radiologist who was not involved in the original PACIFIC trial. In addition to spatial data, the investigators reported times until progression.

Regardless of site, durvalumab was associated with a longer time until progression or death. Although comparative values were not reached for distant or simultaneous spread, median time until local progression or death was reportable, at 25.2 months in the durvalumab group versus with 9.2 months in the placebo group.

These values were available, in part, because local spread was the most common type of progression: It occurred in 80.6% of patients who progressed on durvalumab and 74.5% of progressors in the placebo group.

Durvalumab reduced the rate of progression across the three spatial categories, compared with placebo, including local only (36.6% vs. 48.1%, respectively), distant only (6.9% vs. 13.1%), and simultaneously local and distant (1.9% vs. 3.4%). This means that, at first progression, new distant lesions were found in 8.8% of patients treated with durvalumab, compared with 16.5% of those treated with placebo. Of note, approximately two-thirds of patients with distant progression had only one or two distant lesions, often confined to one organ, most commonly the brain. This pattern of progression was observed in both treatment arms.

According to Dr. Rimner, this finding is clinically relevant because it suggests a potential role for local ablative therapy.

Dr. Benjamin Movsas, chair of radiation oncology at the Henry Ford Cancer Institute in Detroit.

Dr. Benjamin Movsas

Expert perspective on the analysis was provided by Benjamin Movsas, MD, chair of radiation oncology at the Henry Ford Cancer Institute in Detroit.

“The PACIFIC trial has really transformed the standard of care for patients with locally advanced, inoperable non–small cell lung cancer by adding immunotherapy to the prior standard of care combining chemotherapy and radiation, and this has shown a dramatic improvement in survival,” Dr. Movsas said.

“By adding the immunotherapy durvalumab, you can reduce risk of local failure, you can reduce the risk of distant failure, and interestingly enough, when patients do fail distantly, and this is true in both arms, they tended to fail in only one or two spots, which is encouraging because that suggests maybe a window of opportunity to treat those one or two spots, and we have newer technologies that allow us to consider that. So we really have a new paradigm.”

The study was funded by AstraZeneca. The investigators disclosed additional relationships with Merck, Nanobiotix, Boehringer Ingelheim, and others.

SOURCE: Rimner A et al. ASTRO 2019, Abstract LBA6.

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