Michael Rosskamp, Julie Verbeeck, Freija Verdoodt, Harlinde De Schutter

SOCIALE ASPECTEN

SOCIAL INEQUALITIES IN CANCER SURVIVAL IN BELGIUM: A POPULATION-BASED COHORT STUDY

ONDERZOEKSPROJECT

PROBLEEM- EN DOELSTELLING(EN)

In many countries, socioeconomic (SE) inequalities have been reported to be associated with differences in cancer incidence, survival and mortality. However, the direction and magnitude of these associations vary in function of tumour type, outcome and SE parameter, and are linked to the study design, study population and local health care system. Over the last decades, improvements in early detection, diagnosis and treatment have resulted in better survival for most cancer types. However, not everyone equally benefits from this progress: the gap between deprived and affluent patients has increased over time. In this population-based cohort study, we evaluated the association between individual-level SE and sociodemographic (SD) factors and cancer survival for 8 common cancer types in Belgium. Further, we evaluated if observed associations were (partly) explained by specific clinical characteristics such as tumor characteristics, stage at diagnosis, comorbid conditions, and detailed primary treatment information.

ONDERZOEKSOPZET

From the database of the Belgian Cancer Registry (BCR), a random sample of patients diagnosed between 2006 and 2013 aged at least 25 years at time of diagnosis was extracted for each of the studied tumour types (i.e. colon, rectal, female breast, lung, ovarian, head and neck, pancreatic and stomach cancer). Besides patient and tumour characteristics as registered by BCR, primary treatment information was available from reimbursement data provided by the Intermutualistic Agency (IMA/AIM). Information on SE/SD parameters (i.e. income, marital status and position in the labour market) and vital status were derived from the Crossroads Bank for Social Security (KSZ/BCSS), and individually linked to the study cohort using a unique personal identification number. The outcome was 5-year observed survival. Associations between survival and SE/SD factors were assessed using multivariable Cox proportional–hazard regression models. Results were presented as hazard ratios (HR) with 95% confidence intervals (95% CI).

RESULTATEN

A total of 109 591 patients were included. 60 206 patients (54.9%) were women and 38 168 patients (34.8%) were younger than 65 years and non-retired at time of diagnosis. Survival was lower for patients with a low or middle household income compared with those with high income. The association was most pronounced for colon, breast and head and neck cancers. Not working was associated with worse survival for all cancer types, except ovarian cancer. Both job-seeking and not working because of disability/incapacity or other reasons were found to be statistically significantly associated with poorer survival compared with being employed. Marital status was also associated with cancer survival. Overall, living alone (single, separated or widowed) was associated with worse survival than being married or cohabitating. Overall, associations were most pronounced for certain lifestyle-related cancer types (e.g. head

and neck cancers) and those with good to moderate prognosis (e.g. colorectal and female breast cancer).

KLINISCHE- MAATSCHAPPELIJKE- EN/OF WETENSCHAPPELIJKE RELEVANTIE

Being a complex societal concept, SE position consists of cultural, social, and economic dimensions. By investigating multiple SE/SD dimensions separately at the individual-level, this population-based study, including more than 100 000 cancer patients, identified patient groups that may be at highest risk for SE disparities in cancer survival. Despite a comprehensive and nationwide health insurance program where equity in rights and access to healthcare are pursued, SE position appears to be a significant determinant of cancer survival in Belgium. Reasons behind the observed disparities are multiple and complex and should be further examined. This population-based study is the first to assess the association between individual-level SE and SD parameters and cancer survival in Belgium and provides substantial aspects to build a more comprehensive picture of cancer epidemiology in Belgium. Health policy interventions should consider the observed deprivation gap to plan targeted actions to tackle SE disparities in cancer survival.

ALGEMENE INFORMATIE

• Projectverantwoordelijken: Harlinde De Schutter, Freija Verdoodt • Uitvoerders: Michael Rosskamp, Julie Verbeeck, Freija Verdoodt, Harlinde De

Schutter • Organisatie: Belgian Cancer Registry • Contactgegevens: Freija.Verdoodt@kankerregister.org - +32 2 211 08 01 • Termijn project: 1/01/2016 - 31/12/2019 • Financiering: Kom op tegen Kanker • Partners: prof. Sylvie Gadeyne (Vrije Universiteit Brussel), Victoria Sass (PhD student – Sociology Department - Interface Demography) • Publicaties: https://doi.org/10.1158/1055-9965.EPI-20-0721%20