Methods of a national colorectal cancer cohort study: the PIPER Project

Colorectal cancer is one of the most common cancers, and second-leading cause of cancer-related death, in New Zealand. The PIPER (Presentations, Investigations, Pathways, Evaluation, Rx [treatment]) project was undertaken to compare presentation, investigations, management and outcomes by rurality, ethnicity and deprivation. This paper reports the methods of the project, a comparison of PIPER patient diagnoses to the New Zealand Cancer Registry (NZCR) data, and the characteristics of the PIPER cohort.

National, retrospective cohort review of secondary care medical records (public and private) of all cases of ICD-10-AM C18-C20 on the NZCR in the calendar years 2007 and 2008 (main cohort) and an extended sample of Māori and Pacific cases, and non-Māori non-Pacific controls in 2006 and 2009 (extended cohort).

Of the 6,387 patients identified from the NZCR 5,610 (88%) were eligible for PIPER. Reasons for exclusion were non-adenocarcinoma histology (3%) and non-colorectal primary (2%). Data were collected on 3,695 patients with colon cancer, 1,385 with rectal cancer and 466 with cancer of the recto sigmoid junction.

The PIPER Project has generated comprehensive population level data detailing the diagnosis and management of colorectal adenocarcinoma in New Zealand. This will be used to assess the care provided to patients, and the impact of variations in care occurring between patient groups.