Proximal shift of colorectal cancer in the Australian Capital Territory over 20 years

BACKGROUND: Several studies in other countries have demonstrated a change in subsite distribution of colorectal cancer, with increasing proximal cancers. Confirmation of such a change in Australia would have implications for screening and diagnosis of colorectal cancer. AIMS: To determine whether there has been an increase in the proportion of proximal colorectal cancers in Australia, and whether there have been changes in other clinical and pathological aspects of colorectal cancer. METHODS: A study of the hospital files of patients with colorectal cancer diagnosed and treated at all hospitals in the Australian Capital Territory (ACT) between 1989 and 1995 was compared with data from a published study of patients diagnosed between 1969 and 1976. RESULTS: There was a proximal shift of cancers with a significant increase in the proportion of tumours in the hepatic flexure, ascending colon and caecum, more marked for females than males. There was a corresponding reduction in distal colorectal cancers. Time from onset of symptoms to diagnosis decreased, risk factors for colorectal cancer were noted more frequently, and endoscopy replaced barium enema X-ray as the main diagnostic modality. The resectability of cancers increased, stay in hospital and 30 day mortality declined. Despite apparent earlier presentation and improved surgical resectability, the proportion of patients with localised disease (Dukes' stage A and B) had not changed significantly. CONCLUSIONS: We have detected a number of changes in clinical and pathological aspects of colorectal cancer over a 20 year period in the ACT, including a proximal shift in the subsite distribution of colorectal cancer. These changes suggest that proximal and distal colorectal cancers may have a different aetio-pathogenesis, and have implications for the investigation of patients with suspected colorectal cancer and in screening high-risk groups.