Single women who get breast cancer have a higher mortality rate compared to women in a relationship. The same is true of women with low income, a low level of education and women outside the labour market. This is shown by a new research result from Aarhus University.

2021.10.07 | Helle Horskjær Hansen

Working with a group of colleagues, Cathrine Fonnesbech Hjorth has analysed data on the marital status, cohabitation, income, education and employment status of 2,616 women aged 18-55 who were diagnosed with breast cancer in Denmark in the years 2007-2011. Photo: AU Kommunikation.

According to a study carried out by Cathrine Fonnesbech Hjorth and a group of colleagues, single women and women with low socio-economic positions may need extra support and follow-up after being treated for breast cancer. The findings are based on the analysis of data on the marital status, cohabitation, income, education and employment level of 2,616 women who were diagnosed with breast cancer. Photo: AU Communication.

Although the treatment and prevention of cancer has improved in Denmark, the progress made over the past decades has not benefited everyone equally. A study from Aarhus University shows that women who are singles, widoved or seperated, are outside the labour market due to health reasons, and have a shorter education or low income, have poorer chances of surviving their cancer compared to women who are in relationships, employed, and have a longer education or higher income. 

Working with a group of colleagues, Cathrine Fonnesbech Hjorth has analysed data on the marital status, cohabitation, income, education and employment status of 2,616 women aged 18-55 who were diagnosed with breast cancer in Denmark in the years 2007-2011.

Biggest difference in the first five years

"We saw an inequality in mortality, and due to the women’s young age, the risk of dying from other causes is small. So we can therefore expect the mortality to be attributable to a recurrence. And since we didn’t see a higher recurrence rate in our data, our findings suggest an underdiagnosis of recurrences in these women," explains the researcher. 

Of the women who were included in the study, 286 had recurrence in their breast cancer, and of these, 223 died during the ten years that the study lasted. The first five years in particularly showed a difference in the mortality rate. 

Single women had a mortality rate that was 1.8 times higher, and among low-income women, mortality was 1.4 times higher. For women with a low level of education, it was 1.5 times higher, while women who were not working due to health reasons had a mortality rate that was 1.8 times higher. 

The results have been published in the scientific journal BMC Medicine. 

Correlation with the type of breast cancer

The study also showed that the inequality in the increased mortality was linked to the type of breast cancer among the women.

The researchers discovered that the socioeconomic inequality was most pronounced in women with ER+ tumours who received hormonal treatment in the form of the drug Tamoxifen, and less pronounced in women with ER- tumours. For example, the mortality rate after five years was twice as high for single women with ER+ tumours, while among single women with ER- tumours, it was 1.5 times higher compared with married women. 

The mortality rate among women outside the labour market and women with low incomes was also higher if they had ER+ tumours. If they had ER- tumours, it was no different from that of married women and women with high income. 

Tamoxifen is prescribed to women with ER+ tumours after they have undergone surgery and chemotherapy and may be prescribed for up to ten years. Previous research has shown that 22 per cent of the women with ER+ tumours interrupted their treatment before planned, increasing the risk of a recurrence. The study also showed that single women were more likely to interrupt the treatment. 

"This may have contributed to the findings on inequality in survival which we see in our study," says Cathrine Fonnesbech Hjorth. 

The researcher emphasises that it is important to look into the basis for the findings. 

“It’s possible that the single women and women with low socio-economic positions need extra support and follow-up after being treated for breast cancer,” she says. 

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ER+ and ER- tumours

By examining samples of the cancer tumour, it is possible to determine whether it is sensitive to the female hormone oestrogen, which can lead to increased tumour growth – in this case the cancer is classified as oestrogen receptor positive (ER+). If the tumour is non-sensitive to oestrogen, the oestrogen receptor is negative (ER-). 
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Background for the results

• The study is a cohort study.
• Partners: Per Damkier, Odense University Hospital, Department of Clinical Biochemistry and Pharmacology; Bent Ejlertsen, DBCG (Danish Breast Cancer Group) and Rigshospitalet, University of Copenhagen, Department of Oncology; Timothy Lash, Emory University, Department of Epidemiology; Henrik Toft Sørensen, Aarhus University, Department of Clinical Medicine, Department of Clinical Epidemiology; Deirdre Cronin Fenton, Aarhus University, Department of Clinical Medicine, Department of Clinical Epidemiology.
• The study is financed by the Danish Cancer Society and Aarhus University.
• Read the scientific article here: https://bmcmedicine.biomedcentral.com/articles/10.1186/s12916-021-02108-z

Contact

Cathrine Fonnesbech Hjorth.
Aarhus University, Department of Clinical Medicine, Department of Clinical Epidemiology
cfh@clin.au.dk
(+45) 8716 8238

Supervisor
Deirdre Cronin Fenton
Aarhus University, Department of Clinical Medicine, Department of Clinical Epidemiology
dc@clin.au.dk
(+45) 8716 8209