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. 2009 Jan;47(1):73-9.
doi: 10.1097/MLR.0b013e318180913c.

Impact of acquired comorbidities on all-cause mortality rates among older breast cancer survivors

Thomas P Ahern  1 , Timothy L Lash, Soe Soe Thwin, Rebecca A Silliman
Affiliations

Impact of acquired comorbidities on all-cause mortality rates among older breast cancer survivors

Thomas P Ahern et al. Med Care. 2009 Jan.

Abstract

Background: Breast cancer survivors with higher numbers of comorbidities at the time of primary treatment suffer higher rates of all-cause mortality than comparatively healthier survivors. The effect of time-varying comorbidity status on mortality in breast cancer survivors, however, has not been well investigated.

Objective: We examined longitudinal comorbidity in a cohort of women treated for primary breast cancer to determine whether accounting for comorbidities acquired after baseline assessment influenced the hazard ratio of all-cause mortality compared with an analysis using only baseline comorbidity.

Methods: Cox proportional hazards adjusted for age, race/ethnicity, and exercise habits were modeled using (1) only a baseline Charlson index; (2) 4 Charlson index values collected longitudinally and entered as time-varying covariates, with missing values addressed by carrying forward the prior observation; and (3) the 4 longitudinal Charlson scores entered as time-varying covariates, with missing values multiply imputed.

Results: The 3 modeling strategies yielded similar results; Model 1 HR: 1.4 per unit increase in Charlson index, 95% confidence interval (CI): 1.2-1.7; Model 2 HR: 1.3, 95% CI: 1.1-1.5; and Model 3 HR: 1.4, 95% CI: 1.2-1.6.

Conclusions: Our findings indicate that a unit increase in the Charlson comorbidity index raises the hazard rate for all-cause mortality by approximately 1.4-fold in older women treated for primary breast cancer. The conclusion is essentially the same whether accounting only for baseline comorbidity or accounting for acquired comorbidity over a median follow-up period of 85 months.

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Figures

Figure 1
Figure 1
Directed acyclic graph depicting hypothesized relationships among covariates. Boxes indicate variables identified by backdoor test as confounders requiring adjustment. “Therapy” and “Stage” denote breast cancer treatment choices and AJCC disease staging, respectively.
Figure 2
Figure 2
Distribution of observed and imputed Charlson index values by interview month following primary breast cancer surgery.
See this image and copyright information in PMC

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