Date of Graduation

2017

Document Type

Dissertation

Degree Type

PhD

College

School of Pharmacy

Department

Pharmaceutical Sciences

Committee Chair

Usha Sambamoorthi

Committee Co-Chair

Nilanjana Dwibedi

Committee Member

Patricia Findley

Committee Member

Malcolm D Mattes

Committee Member

Xi Tan

Abstract

Coronary artery disease (CAD) is one of the most burdensome chronic conditions in the elderly. The two key goals of long-term management of CAD are (i) to reduce symptoms and ischemia and (ii) prevent myocardial infarction and death, by lowering lipids and blood pressure. Of all the risk reduction strategies, use and adherence to concomitant pharmacotherapy with statins and beta-blockers, angiotensin-converting enzyme inhibitors (ACEIs) or angiotensin II receptor blockers (ARBs) have been shown to be highly effective and has become the cornerstone of CAD management. However, adherence to concomitant pharmacotherapy can be influenced by many factors including the development of other life-threatening conditions such as cancer. To date, no real-world study has assessed how incident cancer can affect adherence to concomitant pharmacotherapy and whether concomitant pharmacotherapy can minimize the negative effects of some cancer treatments on CAD-related morbidity and expenditures among individuals with CAD and incident cancer. To fill the knowledge gap, the three related aims of this dissertation were to analyze: 1) the association between incident breast, colorectal, and prostate cancer diagnosis and adherence to statins and/or ACEIs/ARBs/beta-blockers among elderly fee-for-service (FFS) Medicare beneficiaries with pre-existing CAD; 2) the impact of non-adherence to these medication classes on short-term CAD-related hospitalizations in patients with incident cancer diagnosis; and 3) the impact of incident cancer diagnosis on short-term CAD-related inpatient and outpatient healthcare expenditures. The study used a retrospective observational longitudinal cohort study design was conducted among elderly Medicare FFS beneficiaries with pre-existing CAD and those with incident breast cancer (BC), colorectal cancer (CC), or prostate cancer (PC), using multiple years (2005--2012). The study data was derived from the cancer registry data from Surveillance, Epidemiology and End Results (SEER) program linked with the Medicare claims data, the American community survey census-tract files and Area Health Resource Files. Aim 1 and Aim 3 also included 5% non-cancer random sample of Medicare beneficiaries, residing in SEER regions, with pre-existing CAD. Each individual was observed for 48 months with 24-month baseline (for identification of CAD and baseline characteristics) period, 12-month pre-index, and 12-month post-index periods. In the first aim, only 28.9% of the elderly with CAD were adherent to both statins and ACEIs/ARBs/beta-blockers. In the adjusted analyses, women [AOR = 0.70; 95% CI = 0.58, 0.81; P < 0.0001] and men [AOR = 0.63; 95% CI = 0.51, 0.75; P < 0.0001] with CC and men with PC [AOR = 0.92; 95% CI = 0.85, 0.99; P = 0.022] were significantly less likely to be adherent to both medication classes compared to women and men with NC, respectively. No significant differences in adherence to medications were observed among women with BC compared to women with NC. Even among those using single medication class, women [AOR = 0.64; 95% CI = 0.50, 0.79; P < 0.0001] and men with CC [AOR = 0.59; 95% CI = 0.42, 0.76; P < 0.0001] were significantly less likely to be adherent to that medication class compared to women and men with NC. In the second aim, adherence to both statins and ACEIs/ARBs/beta-blockers was estimated at 31.2% during the 120-day period immediately after cancer diagnosis; 13.7% were not adherent to both medication classes during the same period; 27.4% had CAD-related hospitalizations immediately after cancer diagnosis and this percentage declined to 10.6% during the last four months of the post-cancer period. In the adjusted analyses, those not adherent to both statins and ACEIs/ARBs/beta-blockers were more likely to have CAD-related hospitalization compared to those who were adherent to both medication classes [AOR = 1.82; 95% CI = 1.72, 1.92; P < 0.0001]. In the third aim, overall, CAD-related mean healthcare expenditures at pre-index period accounted for about 32.6%--39.5% of total expenditures among women and 41.5% - 46.8% among men. In the adjusted GLMM, all cancer groups had significantly higher CAD-related healthcare expenditures compared to the non-cancer groups. Women with CC 153% higher expenditures compared to women with no cancer [beta = 0.93, P < 0.0001]. Men with CC had 166% higher expenditures compared to men with NC [beta = 0.98, P < 0.0001]. Further, men and women with CC had 57% and 55% higher expenditures compared to men with PC and women with BC, respectively. In summary, the study findings, collectively, suggest that cancer diagnosis negatively impacts adherence to CAD pharmacotherapy. Reduction in adherence was associated with increase in CAD-related hospitalizations and subsequent increase in CAD-related expenditures. This warrants the integration of cardiovascular care in the elderly diagnosed with cancer. Future studies need to explore whether the emerging collaborative care models, such as medical homes, can reduce inpatient use, and consequently, CAD-related expenditures.

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