The Influence of Comorbidity on Breast Cancer Care and Outcomes in New Zealand

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dc.contributor.advisor Campbell, I en
dc.contributor.advisor Lawrenson, R en Edwards, Melissa en 2020-05-20T23:57:46Z en 2020 en
dc.identifier.uri en
dc.description.abstract BACKGROUND: Patients with breast cancer and concomitant comorbidity have poorer prognosis, which may be related to a reduction in the receipt and efficacy of cancer treatment. The primary aims of this thesis were to: (1) evaluate the influence of comorbidity on standards of treatment for breast cancer; and (2) determine the survival benefits of treatments in relation to comorbidity burden. METHODS: Incident cases of primary breast cancer, diagnosed between 2000 and 2015, were identified from 2 prospectively-collected New Zealand breast cancer registers. Comorbidity severity was measured by C3 index score; derived via linkage with national hospitalisation data. Study 1 provided a descriptive analysis of comorbidity burden amongst the cohort. Study 2 modelled the impacts of comorbidity on breast cancer diagnosis and standards of treatment. In Study 3, propensity scores for the conditional probability of treatment were used to create weighted samples balanced with respect to baseline confounding variables. Treatment effects were estimated from weighted Cox proportional hazards and competing risks regression analyses modelling all-cause and breast cancer mortality. Treatment effect heterogeneity by comorbidity severity was evaluated through interaction tests and subgroup analyses. RESULTS: The study population comprised 12 834 women, with 21.5% possessing at least 1 comorbid condition. Comorbidity was associated with poorer survival, with greatest impact on allcause mortality. Individuals with comorbidity were more likely to have higher stage disease and less likely to receive all treatment modalities. Comorbid patients derived mortality benefits from surgery, adjuvant radiotherapy, and endocrine therapy but not adjuvant chemotherapy. Heterogeneity in treatment effects by comorbidity severity was noted for surgery and endocrine therapy, with reduced benefits at higher levels of comorbidity. CONCLUSIONS: Comorbid women with breast cancer receive less treatment than their noncomorbid counterparts, with reduced mortality benefits for those who do. Inferior survival amongst the comorbid is therefore mediated through mechanisms additional to reduced receipt of treatment. en
dc.publisher ResearchSpace@Auckland en
dc.relation.ispartof PhD Thesis - University of Auckland en
dc.relation.isreferencedby UoA en
dc.rights Items in ResearchSpace are protected by copyright, with all rights reserved, unless otherwise indicated. Previously published items are made available in accordance with the copyright policy of the publisher. en
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dc.rights.uri en
dc.title The Influence of Comorbidity on Breast Cancer Care and Outcomes in New Zealand en
dc.type Thesis en Surgery en The University of Auckland en Doctoral en PhD en
dc.rights.holder Copyright: The author en
dc.rights.accessrights en
pubs.elements-id 802190 en
pubs.record-created-at-source-date 2020-05-21 en

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