Faculty of Medicine, Dentistry and Health Sciences

Paul Salama

Thesis

Treatment and survival trends for rectal cancer in Western Australia: a population-based study

Summary

Colorectal cancer is the most common cancer (excluding skin cancer) and the second-leading cause of cancer death in Australia (Australian Institute of Health and Welfare 2004). Rectal cancers make up approximately a third of all such bowel cancers. Historically, the outcomes for patients with rectal cancer have been worse when compared with colon cancer. This is a result of high rates of local recurrence that occur following treatment (around 30%) and which are almost always fatal (Heriot 2000). Recent trends in the management of rectal cancer have concentrated on improving surgical technique and increased use of adjuvant chemo-radiotherapy. With this approach, specialist centres have significantly improved outcomes for rectal cancer. Yet on a population basis, we have little understanding of the current treatment trends within a defined population and their impact upon survival.

This PhD project will evaluate the treatment modalities and survival outcomes for patients with rectal cancer diagnosed in Western Australia from 1996 to 2006. It aims to define independent predictors for the use of adjuvant chemo-radiotherapy, judge its efficacy, and also define independent predictors for response to that chemo-radiotherapy.

A current hypothesis argues that colorectal cancers derive from stem cells (Ricci-Vitania 2007), while multiple studies have revealed an association between inflammatory infiltrate and improved prognosis. This study aims to define the distribution patterns of stem cells and immune cells within the rectal cancer, judge each cell type’s prognostic significance, and evaluate whether stem-cell or immune-cell density influences the responsiveness of the cancer to adjuvant chemo-radiotherapy.

Why my research is important

There is a relative scarcity of population-based studies of rectal cancer from Australia. Certainly, there have been no population-based studies that solely address the treatment and survival of rectal cancer in Western Australia.

This study will be unique as it focuses on rectal cancer, covers a 10-year period, and will collect data with a population-based linked database, pathology reports and the TOPAZ data. The application of adjuvant therapies has substantial variation in the state, so the study will allow comparison between different treatment groups as survival data is available.

No population-based studies to data have looked at the role of colorectal cancer stem cells, so the study will also be unique for this reason. Similarly, there have been no studies looking at tumour-infiltrating lymphocytes in rectal cancer. While previous studies in this area have included colon and rectal cancer, it was as one group, and the studies were not population-based.