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Adapting the Elixhauser comorbidity index for cancer patients
Hemalkumar B Mehta1, Sneha D Sura2, Deepak Adhikari3
1Department of Surgery, University of Texas Medical Branch, Galveston, Texas.
Insights
The Elixhauser comorbidity index, adapted for specific cancers, slightly outperformed the Charlson comorbidity index in predicting 2-year survival. Individual Elixhauser comorbidities showed the best predictive performance for cancer outcomes.
Area of Science:
- Oncology
- Biostatistics
- Epidemiology
Background:
- Comorbidity indices are crucial for predicting cancer patient survival.
- Existing indices like Elixhauser and Charlson require adaptation for specific cancer populations.
- This study addresses the need for validated comorbidity measures in breast, prostate, lung, and colorectal cancer research.
Purpose of the Study:
- To adapt the Elixhauser comorbidity index for four major cancer types.
- To compare the predictive performance of different versions of the Elixhauser and Charlson comorbidity scores for 2-year cancer survival.
- To identify the most effective comorbidity measure for controlling confounding in cancer outcomes research.
Main Methods:
- Utilized Texas Cancer Registry-linked Medicare data (2005-2011) for patients with breast, prostate, lung, or colorectal cancer.
- Developed cancer-specific weights for Elixhauser comorbidities using competing risk regression in a training cohort.
- Compared Elixhauser and Charlson comorbidity scores using c statistics in a validation cohort.
Main Results:
- Cancer-specific Elixhauser scores demonstrated slightly better prediction of 2-year survival compared to cancer-specific Charlson scores (National Cancer Institute combined index).
- Individual Elixhauser comorbidities exhibited the highest predictive accuracy across all four cancer types.
- Mortality rates varied by cancer type, with lung cancer having the highest 2-year noncancer mortality (14.5%).
Conclusions:
- The cancer-specific Elixhauser comorbidity score offers comparable or superior performance to the cancer-specific Charlson score for predicting cancer survival.
- Individual Elixhauser comorbidities may represent the optimal approach for confounding control in cancer outcomes research, provided sufficient sample size.
- The findings support the use of tailored comorbidity indices for more accurate prognostication in oncology.
Background:
This study was designed to adapt the Elixhauser comorbidity index for 4 cancer-specific populations (breast, prostate, lung, and colorectal) and compare 3 versions of the Elixhauser comorbidity score (individual comorbidities, summary comorbidity score, and cancer-specific summary comorbidity score) with 3 versions of the Charlson comorbidity score for predicting 2-year survival with 4 types of cancer.
Methods:
This cohort study used Texas Cancer Registry-linked Medicare data from 2005 to 2011 for older patients diagnosed with breast (n = 19,082), prostate (n = 23,044), lung (n = 26,047), or colorectal cancer (n = 16,693). For each cancer cohort, the data were split into training and validation cohorts. In the training cohort, competing risk regression was used to model the association of Elixhauser comorbidities with 2-year noncancer mortality, and cancer-specific weights were derived for each comorbidity. In the validation cohort, competing risk regression was used to compare 3 versions of the Elixhauser comorbidity score with 3 versions of the Charlson comorbidity score. Model performance was evaluated with c statistics.
Results:
The 2-year noncancer mortality rates were 14.5% (lung cancer), 11.5% (colorectal cancer), 5.7% (breast cancer), and 4.1% (prostate cancer). Cancer-specific Elixhauser comorbidity scores (c = 0.773 for breast cancer, c = 0.772 for prostate cancer, c = 0.579 for lung cancer, and c = 0.680 for colorectal cancer) performed slightly better than cancer-specific Charlson comorbidity scores (ie, the National Cancer Institute combined index; c = 0.762 for breast cancer, c = 0.767 for prostate cancer, c = 0.578 for lung cancer, and c = 0.674 for colorectal cancer). Individual Elixhauser comorbidities performed best (c = 0.779 for breast cancer, c = 0.783 for prostate cancer, c = 0.587 for lung cancer, and c = 0.687 for colorectal cancer).
Conclusions:
The cancer-specific Elixhauser comorbidity score performed as well as or slightly better than the cancer-specific Charlson comorbidity score in predicting 2-year survival. If the sample size permits, using individual Elixhauser comorbidities may be the best way to control for confounding in cancer outcomes research. Cancer 2018;124:2018-25. © 2018 American Cancer Society.
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