PV QA 4 - Poster Viewing Q&A 4
Purpose/Objective(s): Because radiotherapy (RT) induces beneficial antitumoral immune responses, administering corticosteroids (CS) for other medical issues such as COPD, RT-related toxicity attenuation, is a major oncologic concern. This is the only known study evaluating the impact of CS on outcomes of early-stage non-small cell lung cancer (NSCLC) following stereotactic ablative RT (SABR).
Materials/Methods: A prospectively-registered institutional database of SABR for early-stage non-metastatic NSCLC was queried (2005-2015). CS administration (non-inhaled, regardless of dose/agent) was dichotomized based on two definitions: 1) CS receipt within two days of the SABR course, and 2) CS delivery between up to 6 months before SABR and the date of last follow-up or any progressive disease (LFU/PD). Statistics included Kaplan-Meier survival analysis, Cox proportional hazards modeling, and cumulative incidence analysis utilizing death as a competing risk model evaluated with Gray’s test.
Results: Of 912 consecutive patients, 87 (10%) received CS based on the ± 2-day definition, and 211 (23%) based on the LFU/PD definition. The most common CS agents were prednisone (62%) and dexamethasone (19%); most common CS indications were COPD (34%) and pneumonitis caused by SABR or other previous treatments (24%). Median follow-up was 45 months. Groups were largely well-balanced. Patients receiving CS appears to have a significant change in blood white cell parameters. Although CS administration associated with worse isolated locoregional recurrence-free survival, distant metastasis-free survival, recurrence-free survival, and overall survival on Kaplan-Meier and Cox multivariate analysis, there were no differences in cumulative incidences of recurrence (local, regional, isolated locoregional, distant, any) when using death as a competing risk model, in both CS delivery definitions (p>0.05 for all).
Conclusion: Although further corroboration is required and causation is not implied, these data do not suggest a detriment in outcomes if corticosteroids are administered in proximity with SABR. Individualized judgment in administering CS for these settings is still recommended. These data have implications not only for ongoing cooperative group trials, but also the construction and implementation of immunotherapy-SABR trials.
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