Median overall survival as of the update was 28.7 months with standard-dose radiation therapy, compared with 20.3 months with high-dose radiation therapy (P = .0072), Dr. Bradley and coinvestigators reported. This survival benefit stood up in multivariate analysis (hazard ratio, 1.30; P = .0315).
The standard dose of radiation also yielded better 5-year overall survival (32.1% vs. 23%; P = .007) and 5-year progression-free survival (18.3% vs. 13%; P = .055). Further analyses suggested that these differences were not due to differential radiation therapy compliance.
The high-dose radiation group had more grade 5 adverse events (nine vs. three events), as well as higher rates of treatment-related grade 3 or worse dysphagia (12.1% vs. 3.2%; P = .0005) and esophagitis (17.4% vs. 5.0%; P less than .0001). Pulmonary toxicity was statistically indistinguishable between groups.
Since the RTOG 0617 results were first reported, the standard of care for unresectable stage III NSCLC has changed, as the PACIFIC trial showed an overall survival advantage of adding the immune checkpoint inhibitor durvalumab (Imfinzi) as maintenance therapy after concurrent chemoradiotherapy (N Engl J Med. 2018;379:2342-50).
However, the 2-year overall survival rate with chemoradiation using the standard radiation dose in the former trial (59.6%) is fairly close to that seen with chemoradiation plus maintenance durvalumab in the latter trial (66.3%), the investigators noted.
Dr. Bradley disclosed having a consulting or advisory role with AstraZeneca. The trial was supported by the National Cancer Institute and Eli Lilly.
SOURCE: Bradley JD et al. J Clin Oncol. 2019 Dec 16. doi: 10.1200/JCO.19.01162.