Impact of Systemic Autoimmune Diseases on Treatment Outcomes and Radiation Toxicities in Patients with Stage I Non-Small Cell Lung Cancer Receiving Stereotactic Body Radiation Therapy: A Matched Case-Control Analysis

SIMPLE SUMMARY: Lung cancer is the leading cause of cancer-related deaths worldwide. Stereotactic body radiation therapy (SBRT) has become the standard treatment for inoperable early stage non-small-cell lung cancer (NSCLC). This study explored the relationship between systemic autoimmune diseases (SADs) and SBRT in patients with stage I NSCLC, while eliminating the effects of clinical staging, irradiation techniques, and combination therapies. Our findings indicated that compared to controls, patients with NSCLC and SADs experience poorer prognosis, but an equal incidence rate of radiation pneumonitis, after SBRT. Therefore, we suggest that SBRT should be considered a radical treatment in patients with stage I NSCLC accompanying SADs; however, practitioners must keep the associated poor prognosis in mind. ABSTRACT: We aimed to evaluate the impact of systemic autoimmune diseases (SADs) on treatment outcomes and radiation toxicities following stereotactic body radiation therapy (SBRT) for stage I non-small cell lung cancer (NSCLC). We queried an institution-based database on patients with SADs treated with SBRT for lung cancer between 2001 and 2016 (SAD group). Each patient was matched to three controls without SADs. The primary outcomes of interest were the overall survival (OS) and local control rate (LCR). The secondary outcomes were radiation toxicities of grades ≥2 (≥G2). Twelve patients with SADs were matched to 36 controls. The median follow-up duration was 3.6 years. There was a significant intergroup difference in the OS (hazard ratio [HR]: 4.11, 95% confidence incidence [CI]: 1.82–9.27, p < 0.001) and LCR (HR: 15.97, 95% CI: 2.89–88.29, p < 0.001). However, there were no significant intergroup differences in the odds of acute (odds ratio [OR]: 0.38, 95% CI: 0.02–8.91, p = 0.550) and late (OR: 2.20, 95% CI: 0.32–15.10, p = 0.422) ≥G2 radiation pneumonitis. No other ≥G2 toxicities were identified. In conclusion, although radiation toxicities are not enhanced by SADs, SADs are risk factors of poor prognosis following SBRT for stage I NSCLC.