Survival and Local Control Outcomes Following Palliative Radiation for Malignant Airway Obstruction

Abstract

Palliative radiation may be beneficial for patients with metastatic or locally advanced disease causing malignant airway obstruction (MAO). However, the subset of patients most likely to benefit from palliative airway radiation is unknown. In this study, we seek to report local control and survival outcomes for patients treated with palliative radiation for MAO and provide prognostic factors for improved overall survival.An IRB approved single institution retrospective review of patients treated with palliative thoracic radiation for MAO from 2008-2016 was undertaken. The primary study endpoint was overall survival (OS) and secondary endpoints included local response and airway specific progression free survival. Kaplan-Meier survival, and Cox proportional hazards regression analyses were performed to identify factors associated with OS. Variables with clinical and univariate significance were modelled using multivariate logistic regression analysis.Palliative radiation for MAO was identified for 237 patients (median age of 63.8 yrs). 88.6% of patients were treated for primary lung cancer and 41.6% of those patients had adenocarcinoma histology. At time of analysis, 78.5% patients had died. Median follow-up was 2 months. Out of 116 patients with imaging follow-up: 31.0% had airway specific progression, 68.9% had complete or partial response at last follow up. For those patients with palliative tumor response, median time to progression was 5.0 (Range 1.1-17.8) months. Kaplan-Meier estimate of median overall survival following start of radiation therapy was 5.0 (95% CI 3.8-5.8) months. In multivariable analyses, there was a marginally increased hazard ratio for patients who had dyspnea at rest HR 2.09 (95% CI 0.78-5.62), oxygen requirement at presentation HR 1.28 (95% CI 0.81-2.01), and higher ECOG level 2-4 HR 1.21 (95% CI 0.81-1.80). Conversely, squamous cell histology and treatment with BED10 greater than or equal to 39 (equivalent to the commonly used 30Gy in 10 fraction regimen) were significantly predictive of improved OS, HR 0.56 (95% CI 0.32-0.97) and HR 0.42 (95% CI 0.28-0.64) respectively.To our knowledge, this analysis is the largest collection of patients receiving palliative thoracic radiotherapy for MAO. These data show that MAO is a poor prognostic feature for survival, but treatment responses are seen. Increased BED delivered and squamous cell carcinoma, a radiosensitive tumor histology, were associated with improved survival. These results may help to inform optimized patient selection for and outcomes of patients with MAO receiving palliative RT.