Colorectal cancer in rural regional Australia

Abstract

Colorectal cancer (CRC) is the second commonest cancer in Australia. The survival outcome of colorectal cancer patients within Australia is reported to vary with population density and between health services, with some literature showing poorer prognosis in rural regional and remote patients. Chapter one aims to outline some key issues in CRC such as epidemiology, diagnosis, treatment, surveillance, and outcome whilst chapter two aims to present a systematic review of how geographical disparity influences CRC survival. There are many potential factors that contribute to a poorer prognosis in rural regional CRC patients though the literature is limited, and at times, inconsistent. Thus, there is a need for regular audit, reporting and benchmarking of outcomes in CRC patients against agreed standards.

I reviewed the long-term outcomes of CRC at Barwon Health, which serves the South West Victoria, a region with a population of some 500,000. My aim was to determine whether changes introduced to the management of CRC translated into improved survival after surgery. The literature to date has suggested that patients living in rural and regional Australia (grouped together) have worse colorectal cancer survival rates than those living in metropolitan Australia. This thesis was based on a prospectively maintained registry kept over a period of thirteen years from 2002 to 2014, that had accumulated 1079 patients who had undergone surgery at the University Hospital Geelong for CRC (744 colon cancers and 335 rectal cancers).

The overall number of operations per year increased over time (p=0.037) but with similar proportions of elective and emergency surgery (p=0.75) and tumour stage (P=0.21). This lack of change in the proportion of elective cases was in spite of the Federal Government introducing a National Bowel Cancer Screening Program in 2006. The proportion of patients with severe comorbidities did increase (p=0.015) over the study period. The median survival after surgery by stage was 123 months, 141 months, 76 months and 17 months for stages I to IV CRC respectively. Overall, there were improvements observed in both peri-operative mortality (POMR) (p=0.028) and long- term survival (p=0.0025) of CRC patients in this major regional centre.

I then reviewed the outcome of patients with metastatic disease. The Geelong database included 843 patients who had undergone resection and primary anastomosis for their primary tumour (661 colon cancers, 182 rectal cancers). Metastatic disease was present in 16% (135 patients) and was associated with an increased risk of anastomotic leakage (13% vs. 5%, p=0.003) and a higher peri- operative mortality rate (9.6% vs. 2.8%, p=0.0003). Patients with anastomotic leakage had a reduction in the overall survival (121 months vs. 66 months, p=0.02).

The fifth chapter aimed to perform a regional study to identify patients with colorectal cancer at higher risk of developing metastatic disease. There were 503 patients (345 colon and 158 rectal) with non-metastatic (stage I-III) CRC who had resections and were followed up for at least five years. Metastatic progression was, as expected, significantly higher for patients with stage III disease (aHR 4.42 for colon cancer 95% CI 1.74 to 11.23, aHR 3.34 for rectal cancer 95% CI 1.36 to 8.22), and those with lymphovascular invasion (aHR 2.94 95% CI 1.70 to 5.06). Metastatic disease was also more likely to eventuate in those with severe comorbidities (aHR 2.18, 95% CI 0.26 to 0.86), and in colon cancer patients with the lowest socioeconomic status (aHR 2.03 95% CI 1.23 to 3.34). Gender, tumour location and geographical location (rural or regional) was not associated with metastatic progression. Before determining surveillance strategies targeting higher-risk patient groups in regional Victoria, these findings would require confirmation from similar studies in other regions of rural/regional Victoria, such as Bendigo, Albury / Wodonga, Latrobe Valley, or Shepparton.