Surgery (RMH) - Theses
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ItemInvestigation of colorectal cancer outcomes through the use of state-wide administrative data and data linkage( 2023)Background Healthcare administrative data are data that are collected at each encounter with the healthcare system, as part of routine process. Although primarily not for research purposes, administrative data can be utilised as a low-cost source of information for clinical outcomes research, with broader population coverage compared to clinical databases. The use of population-based data linkage to combine various data sources into a linked record has also become an increasingly valuable epidemiology research tool to attempt to address the deficiencies in a single dataset. The current evidence for the effect of socioeconomic disadvantage (SED) on stage at presentation and survival for colorectal cancer in Australia is conflicting, with varying definitions of advanced stage at presentation. The main aim of this thesis was to evaluate the impact of SED (based on area-level measurements) on stage at presentation and survival in patients who had undergone resections for colorectal cancer. Methods The main methodology underpinning the projects in this thesis utilised administrative data and data linkage to construct a more detailed dataset to report on clinical outcomes, and to allow for more adjustments for potentially confounding co-variables. Data linkage services were provided by the Centre for Victorian Data Linkage (CVDL). The Victorian Admitted Episodes Dataset (VAED) was used to identify all patients who had undergone a colorectal cancer resection in Victoria in 2010-2020, and then linked to the Victorian Cancer Registry (VCR) and the Victorian Death Index (VDI) to provide further sociodemographic, pathology, and survival data. SED was measured using the Index of Relative Socioeconomic Disadvantage (IRSD) in quintiles, an area-level composite measure utilising data from the Australian Bureau of Statistics, available from the VCR. Stage at presentation was grouped into specific Tumour Node Metastasis (TNM) stage groupings that were more or less likely to be symptomatic. Multivariable regression analysis was performed to adjust for potentially confounding covariables. Overall survival was analysed using Cox proportional hazards multivariable regression and odds of presenting with an advanced stage tumour were analysed with multivariable logistic regression. Results These studies found that in patients who had undergone resection for colorectal cancer (8,189 patients over a 10-year period in Victoria), there was no evidence of effect of area-level SED on the odds of presenting with a locally advanced stage tumour, which was more likely to be symptomatic (OR=1.08, CI: 0.92 - 1.28; OR=1.09, CI: 0.92 - 1.29; OR=1.00, CI: 0.84 - 1.19; OR=1.11, CI: 0.92 - 1.35 (SED quintiles 2-5 v. SED quintile 1 (most disadvantaged))). Similarly, there was no evidence of effect of SED on the odds of presenting with an early-stage tumour, which was more likely to be asymptomatic. There was no evidence of association between SED and odds of presenting with a more advanced overall stage (Stage III-IV versus Stage I-II). There was no evidence of difference in overall survival comparing patients from different quintiles of SED (HR = 0.96, CI: 0.86 - 1.07; HR = 0.99, CI: 0.88 - 1.11; HR=0.94, CI: 0.84 - 1.06; HR=1.04; CI: 0.91 - 1.18 for SED 2-5 respectively compared to SED 1 (most disadvantaged)). Conclusion The large, detailed studies in this thesis found no evidence that area-level SED was associated with differences in stage at presentation or with poorer overall survival on colorectal cancer resection patients in Victoria. While data regarding symptomatic versus asymptomatic presentations is lacking in registries, these results provide indirect evidence that presentation with less likely symptomatic and more likely symptomatic colorectal cancer may be similar across SED groups in patients undergoing CRC resections.