Patients with early-stage non-small cell lung cancer (NSCLC) may be more or less responsive to stereotactic body radiation therapy (SBRT) based upon histological classification, according to a study published in the Journal of Thoracic Oncology.
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SBRT is considered standard of care for patients with early-stage NSCLC that is deemed inoperable. SBRT’s use has been optimized by the identification of tumor- and treatment-related factors that predict failure, such as larger tumor size and lower radiation doses. However, it is unknown whether histologic subtypes within NSCLC are more likely to respond to SBRT.
A study led by Neil M Woody, MD, Department of Radiation Oncology, Cleveland Clinic (Ohio), investigated the impact of histological subtype and tumor heterogeneity on SBRT treatment success. Researchers sampled 740 patients with early-stage NSCLC who were treated with SBRT from 2003 through 2015. Patients were grouped into four categories by tumor type: adenocarcinoma, squamous cell carcinoma, unknown, and NSCLC not otherwise specified. Patient age, sex, body mass index, performance status, length of follow-up, and radiotherapy dose were equally balanced within the sample. Cumulative incidence curves were calculated using the competing risk method, and predictors of local failure were identified using Fine and Gray regression.
In total, 72 patients had a local failure, with a cumulative incidence of local failure at 3 years of 11.8%. Univariate analysis showed squamous cell carcinoma histological subtype, younger age, fewer medical comorbidities, higher body mass index, higher positron emission tomography standardized uptake value, central tumors, and lower radiation dose all to be associated with an increased risk for local failure. Upon multivariable analysis, squamous cell carcinoma histological subtype (HR = 2.4, P = .008) was the strongest predictor of local failure. Patients with squamous cancers failed SBRT at a higher rate (3-year cumulative rates of local failure of 18.9%) than those with adenocarcinomas (8.7%) or NSCLC not otherwise specified (4.1%).
Authors of the study concluded that squamous cell carcinomas have a significantly higher rate of local failure after SBRT treatment than other NSCLCs. Implications of the study are far-reaching.
"This study is the first demonstration of a histological basis for local failure after SBRT. The clinically significant implication of our study is that SBRT treatments should be optimized on the basis of histological subtype," the authors commented.
