Review articleSocioeconomic inequalities in prostate cancer survival: A review of the evidence and explanatory factors
Introduction
Prostate cancer has emerged as one of the most prevalent cancers worldwide (Bray et al., 2013). Particularly in Europe, North America and Australia prostatic neoplasms are widespread. In terms of inequalities studies mostly have shown higher incidence rates among higher socioeconomic status (SES) groups (Aarts et al., 2010, Clegg et al., 2009, Faggiano et al., 1997, Gilligan, 2005, National Cancer Intelligence Network, 2009, Shafique et al., 2012a). Studies analysing population-based prostate cancer mortality data found inconsistent associations with SES (Albano et al., 2007, Elstad et al., 2011, Krieger et al., 2012, Menvielle et al., 2008). Therefore, it is remarkable that previous overviews highlighted lower survival rates and higher excess mortality especially for lower status groups among prostate cancer patients (Coleman et al., 2004, Gilligan, 2005, Kogevinas and Porta, 1997, Kravdal, 2000, Quaglia et al., 2013, Woods et al., 2006) whilst overall, the survival concerning prostate cancer has improved (De Angelis et al., 2014). One can assume that the identification of potential explanatory factors could point to reduce inequalities, and furthermore the number of avoidable deaths (Ellis et al., 2012). Moreover, as survival is considered as a potential quality of care indicator for prostate cancer, improvements in health care could be deduced (Spencer et al., 2003).
Information about underlying causes to explain socioeconomic differences in prostate cancer survival and case fatality is sparse. Possible explanations can be divided into three groups (Auvinen and Karjalainen, 1997, Frederiksen et al., 2009, Woods et al., 2006): factors linked to the tumour (stage at diagnosis, biological characteristics), the patient (comorbidity, health behaviour, psychosocial factors) and the health care (treatment, medical expertise, screening).
There is an ongoing discussion about the role of health care management as a contributing factor to social disparities in survival among prostate cancer patients (Chu and Freedland, 2010). For instance, Lyratzopoulos et al. (2010) found out that patients from England with lower SES were less likely to receive radical surgery or radiotherapy (and watchful waiting more likely) than those from least deprived SES groups, also when age, disease stage, period of diagnosis, tumour type or hospital (but not comorbidity) were taken into consideration. Data from other studies conducted in England, Australia and the USA also has shown that socioeconomically disadvantaged men have a decreased likelihood of having radical prostatectomy compared to patients with lower SES who received more often hormone therapy, active surveillance, watchful waiting and partly radiation (Fairley et al., 2009, Hayen et al., 2008, Krupski et al., 2005). Furthermore, screening uptake is lower among prostate cancer patients with low SES in different health care settings (Ross et al., 2011, Williams et al., 2011). Also, stage at diagnosis is discussed extensively as an explanatory factor (Auvinen and Karjalainen, 1997, De Angelis et al., 2014, Woods et al., 2006). Recent Anglo-American studies have shown an association between lower SES and an advanced stage at diagnosis for prostate cancer while adjusting for several covariates (Clegg et al., 2009, Lyratzopoulos et al., 2013). Moreover, patient factors as comorbidity or health behaviour can interact with treatment modalities or disease stage and additionally have a potential impact on inequalities in survival (Berglund et al., 2011, Hall et al., 2005b). Berglund et al. (2011) report in their study an increased likelihood of surveillance as treatment among patients with severe comorbidity while radical prostatectomy was significantly less likely to be offered. Furthermore, all cause and competing cause mortality but not prostate cancer specific mortality was higher in patients with severe comorbidity.
However, despite the increasing efforts in research about social disparities in prostate cancer survival, the latest comprehensive (non-systematic) overview dates back to nearly one decade (Woods et al., 2006). It comprises 14 studies reporting data for prostate cancer patients, and moreover, it is still unclear which are the most relevant factors contributing to the differences. Therefore, a systematic review was conducted to address two major topics: first, to give a current overview of the studies and their evidence about the association between socioeconomic status and prostate cancer survival since 2005, and second, to work out which explanatory factors contribute to these differences following Woods et al. (2006) and Auvinen and Karjalainen (1997). Thus, patient, disease and health care factors are considered as potential mediators.
Section snippets
Methods
A systematic review in the PubMed database was performed on the basis of the PRISMA guidelines (Moher et al., 2009) using a combination of following keywords in title and abstract: socio*, inequalit*, income, education*, occupation*, survival, excess mortality, case fatality, prognosis, prostate, cancer, common cancer*, major cancer*, cancer site*. The search strategy was completed by the two MeSH Terms ‘prostatic neoplasms’ and ‘survival analysis’. Publications that have been released between
Results
The PubMed search generated 330 publications that were screened by title and abstract resulting in 78 potential relevant articles. Of these, 40 were included in this review after extensive full-text screening. Main reasons for exclusion were that indicators of SES were missing in the analyses or SES was just introduced as confounding variable without presenting its impact on survival, no survival analyses among a patient cohort were conducted, no prostate cancer but other cancer sites were
Discussion
This is the first review since 2005 that gives a systematic overview of the evidence about social inequalities in survival among prostate cancer patients. An apparent majority of the studies (about 75%) supports and widens the findings of former reviews and studies investigating the association between SES and survival regarding this neoplasm (Coleman et al., 2004, Kogevinas and Porta, 1997, Schrijvers et al., 1995, Schrijvers and Mackenbach, 1994, Woods et al., 2006). Men with lower SES have
Conclusion
The reduction of inequalities in survival regarding one of the most prevalent tumour sites worldwide is a major public health concern. The review illustrates the current relevance of this topic despite various improvements in diagnosis and treatment of prostate cancer. Furthermore, there is an ongoing discussion if social inequalities in cancer survival have widened and no definitive evidence could be given (Kravdal, 2013b). Even though a publication bias potentially could have limited the
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