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. 2009 Nov 5;181(3):264–269. doi: 10.1164/rccm.200907-1064OC

TABLE 4.

INSTRUMENTAL VARIABLE ANALYSIS OF THE EFFECTIVENESS OF RADIATION THERAPY FOR UNRESECTED STAGE I AND II NON–SMALL CELL LUNG CANCER

Health Care Service Area
Probability of RT Use
Adjusted Survival* High Utilization Low Utilization High Utilization Low Utilization IV Estimator (95% CI)
Overall
 12-mo 58.8% 56.6% 64.7% 50.4% 15.6% (2.0%–33.9%)
 24-mo 38.1% 35.6% 18.1% (2.2%–38.0%)
Lung cancer-specific
 12-mo 64.4% 61.2% 64.7% 50.4% 21.6% (0%–29.6%)
 24-mo 45.0% 40.9% 26.3% (0.2%–36.4%)

Definition of abbreviation: IV = instrumental variable; RT = radiation therapy.

*

Adjusted survival was calculated using Cox regression adjusting for sociodemographic characteristics, comorbidities, and stage.

Represent Health Care Service areas with high use of radiation therapy.

The IV estimator was calculated as the difference between adjusted survival in the highest and lowest utilization areas, divided by the difference in the probability of undergoing radiation therapy among lung cancer patients in these regions.