Radiotherapy for Lung Cancer in the Intensive Care Unit: A Population-Based Analysis

Abstract

The use of radiotherapy (RT) in lung cancer patients admitted to the Intensive Care Unit (ICU) is poorly described. The purpose of this study is to evaluate characteristics, outcomes, and RT utilization in a population-based cohort of ICU lung cancer patients in Ontario, Canada. Eligible patients between April 1, 2007, and March 31, 2014, were identified through provincial administrative healthcare databases. As eligible patients could receive multiple RT deliveries, each was analyzed separately as an episode of care. Significant differences in patient, treatment, institution, and tumor characteristics between RT and non-RT groups were compared with t-tests for continuous variables and chi-square tests for categorical variables. Pre-ICU disposition was abstracted, stratified by ER admission, same institution admission, or different institution transfer. The Kaplan-Meier method was used to estimate overall survival (OS), measured from index ICU admission to death, censoring at the end of the observation period. Differences in OS between the RT and non-RT groups were compared using the log-rank test. Univariable and multivariable Cox proportional hazard modeling were performed to assess the effect of RT on survival. For all analyses, a P-value threshold of <0.05 was used to define statistical significance. In the 13,739 unique patients meeting the inclusion criteria, RT was delivered in 133 episodes to 1.0% (n = 131) of patients. The RT group tended to be younger (median age 65 vs. 68, P < 0.001), on some form of ventilation (79.8% vs. 38.2%, P < 0.001) and with longer ventilation durations ((median [IQR]) 6 [1-11] vs. 0 [0-2] days, P < 0.001). Pre-ICU disposition in RT patients was more likely to be from the ER (28.2% vs. 21.9%, P = 0.002) or via transfer (35.3% vs. 9.7%, P < 0.001). RT delivery varied across geographic regions (Local Health Integration Network, LHIN), with more than half of the 14 LHINs treating ≤ 5 patients each. In non-RT patients, institutional transfer was less common, ranging from 2.6% to 13.5% across LHINs. In contrast, 2 LHINs accounted for the majority (21.5% and 31.9%, respectively) of transfers in the RT group. While ICU discharge was common in both RT (n = 75, 56.4%) and non-RT (n = 10,405, 71.4%) cohorts, 1-year OS was poor with both groups, but most notably in the RT group (11.3% vs. 42.4%). RT was associated with inferior 1-year OS on unadjusted modeling (HR = 1.99, 95% CI = 1.65-2.38, P < 0.001), with ventilation status and pre-ICU disposition adjusting this finding towards the null on multivariable modeling (HR = 1.17, 95% CI = 0.97-1.40, P = 0.095). Lung cancer patients in the ICU have a poor OS. Although the use of RT in this setting is rare, geographic disparities exist in its utilization in a publically funded healthcare system. Those receiving RT are more likely to present via transfer or the ER, with a significant proportion achieving discharge and a minority prolonged survival, suggesting that RT use may not be futile.