Authors Yu XQ, Luo Q, Smith DP, O’Connell DL and Baade PD
Review Date June 2014
Citation Med J Aust 2014; 200 (1): 586-590
In Australia it has been known for some time that place of residence is associated with disparities in cancer survival, including prostate cancer survival, with patients in rural and remote areas having poorer survival. Although policies and programs have been implemented to address the urban-rural disparities, geographic differences in prostate cancer survival may not have improved. Given it has been shown that PSA testing rates are higher in capital cities than other areas, it may be that men in urban areas are having more early stage cancers diagnosed than those in rural areas, which could go some way to explain the differences in survival; cancer stage at diagnosis is therefore important to consider.
The authors aimed i) to determine whether the previously reported urban–rural differential in prostate cancer survival was evident after adjusting for demographic and clinical factors, and ii) with an extra 11 years data following the authors’ previous report, to investigate temporal trends in the urban-rural inequalities in prostate cancer survival.
Data from the NSW Central Cancer Registry on all first primary prostate cancers diagnosed in 18-84 year-old men between 1982 and 2007 (excluding cases reported only on death certificate or postmortem diagnoses) that were prevalent cases in 1992-2007 were used in the analysis. The outcome variable was all-cause survival time after diagnosis up to 2007, obtained through record linkage with NSW death databases. Predictor variables included place of residence (major cities, inner regional and rural), and area-based measures of socioeconomic status and a proxy measure of PSA testing as well as age at diagnosis (18-64, 65-74, 75-84 years) and spread of disease at diagnosis (localised, non-localised and unknown).
Survival relative to the general population was calculated using period analysis using 3 at-risk periods: 1992-1996, 1997-2001, 2002-2007. Poisson regression was used to adjust for prognostic factors. Estimates of relative excess risk (RER) of death (other areas compared to major cities) over 10 years of follow-up in relation to geographic remoteness after adjusting for other prognostic factors were derived from the model.
68,686 men diagnosed with prostate cancer from January 1982 to December 2007 in New South Wales were included in the analysis. 67.8% lived in major cities; 47.7% had localised disease and 42.5% stage unknown. Men in inner regional or rural areas less likely to have localised disease and more likely to have cancer of unknown stage than those in cities, and incidence rates were also higher.
Overall, 10-year survival increased during the study period, increasing from 57.5% in 1992–1996 and 75.7% in 1997–2001 to 83.7% in 2002–2007; trends observed across categories of geographic remoteness and socioeconomic status. Urban–rural differentials were significant (P < 0.001) after adjusting for five important prognostic factors, with men living outside major cities having higher risk of death from prostate cancer (RER, 1.18 and 1.32 for inner regional and rural areas, respectively). Socioeconomic status was also a significant factor (P < 0.001) for prostate cancer mortality; the risk of dying was 34% to 40% higher for men living in socioeconomically disadvantaged areas than those living in least disadvantaged areas. There was no evidence that this inequality was reducing across time periods, particularly for men living in inner regional areas.
Although overall prostate cancer survival has improved over time, the urban–rural disparity in prostate cancer survival has not, despite policies to address inequality in outcomes across regions. The authors note that there is an urgent need for data on tumour characteristics, treatment and comorbid conditions, to help understand why these inequalities exist so that interventions and policy changes can be informed by good evidence.
Points to Note
- The survival of men diagnosed with prostate cancer in NSW improved quite dramatically from 1992 to 2007 with a 10 year survival rate of 83.7% in 2002-2007.
- However, men living outside major cities had poorer survival outcomes. This was a similar finding to past studies, suggesting any policies to address disparities by regions have not been effective.
- Unfortunately, 43% of men in the study had cancer of “unknown” stage which meant it was difficult to determine the effect of possibly higher rates of earlier stage prostate cancers in major cities due to greater PSA testing although sensitivity analyses suggested it would not explain the regional differences.
- It was not clear why regional and rural areas of NSW had higher incidence of prostate cancer as this would not support the supposition that PSA testing is higher in cities.
- The study could not determine the exact factors responsible for the differences in survival but the authors suggest access (or lack of access) to follow-up services may be implicated as well as lower socioeconomic status in areas outside major cities.
- Data on tumour characteristic, treatment and co-morbid conditions are needed to precisely determine the factors contributing to the observed differences in survival across regions so that appropriate interventions can be implemented to reduce the inequality in prostate cancer outcomes in NSW and potentially the rest of Australia.