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. Author manuscript; available in PMC: 2011 Jan 1.
Published in final edited form as: N Engl J Med. 2010 Jun 7;363(1):24–35. doi: 10.1056/NEJMoa0912217

Figure 2. Classification of the Study Patients into Risk-of-Death Categories and Kaplan–Meier Estimates of Overall Survival According to Those Categories.

Figure 2

Recursive-partitioning analysis was used to identify prognostic factors with the most influential predictive significance in a proportional-hazards model of overall survival and to classify patients into categories of low, intermediate, or high risk of death. The prognostic factors in the analysis were age, tumor stage, nodal stage, race, smoking status, HPV status, anemia status, performance status, treatment assignment, and sex. Panel A shows the resulting classifications. Panel B shows data for overall survival in the classified patients. The Kaplan–Meier curves are shown in black, and the associated 95% confidence intervals in gray. The 3-year rates of overall survival were 93.0% (95% CI, 88.3 to 97.7) in the low-risk group, 70.8% (95% CI, 60.7 to 80.8) in the intermediate-risk group, and 46.2% (95% CI, 34.7 to 57.7) in the high-risk group. Hazard ratios for death among the 266 patients for whom the risk classification could be made on the basis of the recorded data and among all 433 patients with oropharyngeal cancer (after missing data on HPV status and number of pack-years were estimated with the use of statistical imputation) were as follows: 3.54 (95% CI, 1.91 to 6.57) and 2.67 (95% CI, 1.54 to 4.62), respectively, in the intermediate-risk group versus the low-risk group; and 7.16 (95% CI, 3.97 to 12.93) and 5.23 (95% CI, 3.14 to 8.73), respectively, in the high-risk group versus the low-risk group.