Colorectal cancer and socio-economic circumstances in the West of Scotland

Oliphant, James Raymond (2013) Colorectal cancer and socio-economic circumstances in the West of Scotland. MD thesis, University of Glasgow.

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Colorectal cancer is a significant cause of morbidity and mortality in the West of Scotland. Socio-economic circumstances are known to be related with variations in health behaviour, risk factor exposure and outcome for a variety of diseases. However, the relationship between socio-economic circumstances and the risk of developing and surviving from colorectal cancer have been inconsistently reported using a variety of methodological approaches over recent decades in this region. Therefore, the principal aim of this body of work was to explore the relationship between socio-economic circumstances and the mortality, incidence and survival from colorectal cancer in the West of Scotland using robust methodology.

Firstly, a population-based study was undertaken to explore recent temporal trends in colorectal cancer-specific mortality and the relationship with socio-economic circumstances. Incidence data from the Scottish Cancer Registry (SMR06) were linked to General Registry Office for Scotland (GROS) death records to produce age-standardised colorectal cancer-specific mortality rates. From 1985 to 2007, both colon and rectal cancer-specific mortality fell among women but remained unchanged in men. From 1996 to 2007, increasing levels of socio-economic deprivation were associated with higher rates of rectal cancer-specific mortality in both sexes and colon cancer-specific mortality in males only. This socio-economic inequality accounted for an estimated 859 excess deaths from colorectal cancer over 12 years in the West of Scotland. Further study of the underlying influences of the association between socio-economic deprivation and colorectal cancer-specific mortality was subsequently performed.

Secondly, a population-based study to explore temporal trends in colorectal cancer incidence and the relationship with socio-economic circumstances was performed. Incidence data from the SMR06 were used to produce age-standardised incidence rates of colorectal cancer. From 1981 to 2007, colon and rectal cancer incidence rates increased significantly among men while remaining stable among women. From 1996 to 2007, the incidence rate of colon cancer in either sex and female rectal cancer were not associated with socio-economic circumstances. However, from 2002 a relationship between deprivation and a higher incidence of male rectal cancer became evident due to a significant reduction in incidence among the most affluent men. This emerging socio-economic inequality accounted for an estimated excess of 286 cases of male rectal cancer over the 6 year period to 2007.

Subsequently, a detailed examination of temporal trends in relative survival following the diagnosis of colorectal cancer was performed. The relationship between survival from colorectal cancer and socio-economic circumstances was also examined using a population-based approach. SMR06 and GROS death record data were linked and relative survival analyses were performed. From 1991 to 2005, 5-year relative survival from colon and rectal cancer significantly improved in both sexes, especially in the first year after diagnosis. From 1996 to 2005, deprivation was associated with poorer survival from male colon cancer and rectal cancer in both sexes. This “deprivation gap” at 5 years arose due to early survival differentials between socio-economic groups in the first year after diagnosis. Furthermore, patients from the most deprived areas were more likely to be older at diagnosis, have rectal tumours, present with more advanced stage disease and were more likely to undergo non-curative treatment compared to the most affluent group. The association between deprivation and poorer survival was also found to become progressively stronger as stage of disease became more advanced. Even after adjustment for other factors associated with survival, deprivation remained independently associated with poorer survival, especially in the first year after diagnosis.

Finally, to examine the association between socio-economic circumstances and short and longer-term survival after surgery for colorectal cancer, a study using clinical audit data linked to SMR06, Scottish Inpatient and Day-case Morbidity (SMR01) data and GROS death records was performed. From 2001 to 2004, this study confirmed that deprivation was independently associated with poorer post-operative (<30 days) and 5-year relative survival following surgery for colorectal cancer. Higher post-operative mortality among patients from more deprived areas was the main determinant of the longer-term deprivation gap in survival. This suggests that the main determinant of the observed longer-term socio-economic survival gradient occurred within the early post-operative period in patients undergoing surgery for colorectal cancer. Poorer short-term survival after surgery is likely to be influenced by higher levels of medical co-morbidity and reduced physiological reserve among more deprived groups.

Therefore, by using a variety of data sources and robust methodological approaches, this thesis explores the relationship between socio-economic circumstances and colorectal cancer mortality, incidence and survival over recent decades in the West of Scotland. It demonstrates that deprivation was associated with poor short and longer-term survival, high cancer-specific mortality rates and became associated with higher rates of male rectal cancer incidence in the West of Scotland. These findings suggest that early survival differentials play a significant role in the observed deprivation gap in longer-term outcomes. Successful strategies to tackle this inequality are likely to involve multimodal interventions aimed at overall health improvements that are equitable to all. Strategies to improve early detection of colorectal cancer including national bowel screening initiatives and public health campaigns need to be further evaluated and, should they prove effective, tailored to ensure that high risk groups are engaged to participate. Additional interventions aimed at reducing post-operative mortality and morbidity in high risk individuals may also help reduce the observed socio-economic inequality in longer-term outcome. However, further detailed research using high-resolution prospectively collected clinical audit data is required so that modifiable determinants of socio-economic survival inequality can be identified to target future interventions.

Item Type: Thesis (MD)
Qualification Level: Doctoral
Keywords: colorectal cancer; socio-economic circumstances; deprivation; epidemiology; incidence; mortality; relative survival; west of scotland
Subjects: R Medicine > RA Public aspects of medicine
R Medicine > RD Surgery
Colleges/Schools: College of Medical Veterinary and Life Sciences > Institute of Health and Wellbeing > Public Health
Supervisor's Name: Morrison, Dr. David S. and Horgan, Prof. Paul G.
Date of Award: 2013
Embargo Date: 24 September 2016
Depositing User: Mr James R Oliphant
Unique ID: glathesis:2013-4596
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 01 Oct 2013 07:52
Last Modified: 31 Aug 2015 08:50

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