Accelerated Hypofractionated Radiation Therapy For Centrally Located Lung Tumors Not Suitable For Stereotactic Body Radiation Therapy (Sbrt) Or Concurrent Chemoradiotherapy (Crt)

In our institution, accelerated hypofractionated radiotherapy is a treatment option for 1) stage I lung non-small cell lung cancer (NSCLC) patients whose tumors are too bulky or too centrally located for SBRT; and 2) select stage II-III NSCLC patients who are not candidates for concurrent CRT. The purpose of this project was to review the clinical outcomes of a large single institutional experience of treating such patients with a dose of 60 Gy in 15 fractions in an era when SBRT was routinely used in clinical practice for early stage lung cancer. Central tumors were defined as the gross target volume being in contact with mainstem bronchi, trachea, esophagus, great vessels, or heart. All patients who received 60 Gy in 15 fractions treated between 2008 and 2017 were reviewed. Competing risk analysis was used to calculate the cumulative incidence of local failure (LF), regional failure (RF), and distant failure (DF). Kaplan-Meier methodology was used to calculate overall survival (OS). Univariate analyses were used to look for potential predictive factors. Eighty-nine patients were treated. Median follow up time was 24.0 months (range: 6.1-94.2 months). Median age of patients was 79.4 years and most tumors were adenocarcinoma (n=47, 52.8%), followed by squamous cell carcinoma (n=31, 34.8%). Thirty patients (33.7%) had stage I disease, 47 patients (52.8%) had stage II-III disease, and 12 patients (13.5%) had stage 4 disease (mostly oligometastatic). Cumulative incidence of LF was 15.3% at 2 years. In those with stage I-III disease, the cumulative incidence of RF and DF were 12.9%, and 28.5%, respectively at 2-years. OS was 74.9% at 2 years, with a median OS of 39.4 months for those with stage I-III disease. In the subset of those with stage II-III disease, the median OS was 38.1 months and 2 year OS was 67.7%. Tumor stage, histology, EGFR mutation status, and location were not found to be statistically significant predictors for any outcomes, although tumor size > 3.5cm was borderline significant in predicting for a higher cumulative incidence of LF (subdistribution hazard ratio = 2.726; 95% confidence interval 0.995-7.469; p=0.051). The most common toxicity was radiation pneumonitis (n=6, 6.4%). The cumulative incidence of any grade 3 toxicity was 10.8% at ≥ 1 year. There were no deaths or hospitalizations directly attributed to treatment. Accelerated hypofractionated radiotherapy to a dose of 60 Gy in 15 fractions resulted in favorable outcomes in NSCLC patients who were not suitable for SBRT or concurrent CRT. Patients with Stage II-III disease had good OS despite not receiving concurrent chemotherapy. Severe toxicities were uncommon.