Cancer-related hospitalisations and ‘unknown’ stage prostate cancer: a population-based record linkage study

OBJECTIVES: To identify reasons for prostate cancer stage being recorded as ‘unknown’ in Australia's largest population-based cancer registry. DESIGN: Prospective population-based cohort. SETTING: New South Wales (NSW) is the most populous state in Australia, with almost one third of the total national population. PARTICIPANTS: NSW Cancer Registry (NSWCR) records for prostate cancer cases diagnosed in 2001–2009 were linked to the NSW Admitted Patient Data Collection (APDC) for 2000–2010. All patients in this study had a minimum of 12 months follow-up in the hospital episode records after their date of diagnosis as recorded by the NSWCR. MAIN OUTCOME MEASURES: Incidence of ‘unknown’ stage prostate cancer and cancer-specific survival. RESULTS: Of 50 597 prostate cancer cases, 39.9% were recorded as having ‘unknown’ stage. Up to 4 months after diagnosis, 77.2% of cases without a hospital-reported cancer diagnosis were recorded as having ‘unknown’ stage. Among those patients with a hospital-reported cancer diagnosis, stage was ‘unknown’ for 7.6% of cases who received a radical prostatectomy (RP) and for 34.0% of cases who had procedures other than RP. In the latter group, the factors that were related to having ‘unknown’ stage were living in disadvantaged areas (adjusted OR (aOR) range: 1.13 to 1.20), attending a private hospital (aOR range: 1.25 to 2.13), having day-only admission for care (aOR=1.23, 95% CI 1.11 to 1.36), or having procedures other than multiple procedures with imaging (eg, biopsy only, aOR range: 1.11 to 1.45). CONCLUSIONS: Over half of ‘unknown’ stage prostate cancer cases did not have a hospital-reported prostate cancer diagnosis within the 4 months after initial diagnosis. We identified differences in the likelihood of cases being recorded as ‘unknown’ stage based on socioeconomic status and facility type, which suggests that further investigation of reporting practices in relation to diagnostic and treatment pathways is required.