The impact of socioeconomic factors on 30-day mortality following elective colorectal cancer surgery: A nationwide study
Introduction
As surgical techniques and adjuvant therapy improve, it becomes more and more relevant to focus on areas such as socioeconomic status and lifestyle in the search for improving the outcome of colorectal cancer. In a society like the Danish one, with equal access for all to the health care system, colorectal cancer patients undergoing elective surgery should have the same chances of surviving the first 30 days after surgery, independent of socioeconomic status (SES). However, there is increasing evidence that a social gradient exists in several colorectal cancer outcomes such as screening participation,1, 2, 3 stage at diagnosis,4, 5, 6 and long-term survival.7, 8, 9, 10, 11 Disparities between social groups in relation to the stage of disease at diagnosis, to the treatment received in hospital and also to pre-hospital factors such as lifestyle and comorbidity may result in different risks of postoperative death for the different social groups. Recently, a British study found that social deprivation was associated with higher postoperative mortality.12
The unique Danish person identification system when linked to the nationwide clinical database of the Danish Colorectal Cancer Group (DCCG) and the social registers in Statistics Denmark made it possible to get individual socioeconomic information on colorectal cancer patients. The aim of the study was to investigate the impact of the SES indicators such as income, education, and housing status on postoperative mortality in electively operated colorectal cancer patients, and to assess whether social inequalities were explained by factors related to patient, disease or treatment.
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Materials and methods
The study population was derived from the national colorectal cancer database, which includes about 93% of patients diagnosed in Denmark with a first-time adenocarcinoma of the rectum or colon.13 The primary study sample included 12,236 patients diagnosed between 1st May 2001 and 31st Dec 2004. Due to various reporting errors, 52 of these patients were excluded, as were 670 patients not having surgery, 1090 patients having a palliative intended operation (i.e. ostomy only and explorative
Results
Of the 7160 patients included in the study population, 342 died during the first postoperative 30 days, resulting in a surgical mortality of 4.8%. Baseline characteristics are summarised in Table 2. Patients who died within 30 days had a higher mean age than patients who survived, 74 versus 68 years, and were more likely to be men, to live in rental housing, to have more advanced tumour stage and ASA stage, and were less likely never to have smoked. Likewise, the average household income was
Discussion
This nationwide Danish study showed a pronounced and inverse relation between SES and 30-day mortality after elective surgery for colorectal cancer. The social gradient was expressed by several SES parameters, i.e. income, education and housing status. Furthermore, the study found that the inequality was accounted for by patient factors (comorbidity and lifestyle), but not by treatment and disease factors.
Only one previous study had to our knowledge investigated the association between SES and
Conflict of interest statement
None declared.
Ethical approval
The project did not require approval by the Regional Committee on Biomedical Research Ethics.
Acknowledgements
The authors are grateful to Lisbeth Nørgaard Møller for statistical assistance and helpful discussions.
Grants: This work was supported by The Danish Cancer Society [DP05043] and The Health Insurance Foundation [2008B084].
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