Breast cancer is the most common cancer in the UK
There is a genetic explanation for why women from poor backgrounds are less likely to beat breast cancer, Dundee University researchers have said.
Poor lifestyles may trigger a key gene mutation linked to worse prognosis, the British Journal of Cancer reports.
The researchers tested samples from 246 women and found that a woman's postcode could be connected to the "health" of the p53 gene in her tumour cells.
Cancer charities said adopting a healthy lifestyle was advantageous.
The link between socio-economic status and a poorer outcome from various cancers has been detected before, with both unhealthier lifestyles and a tendency to be diagnosed later blamed for the differences.
The Dundee research offers more clues as to how those lifestyles may interfere with the body's ability to protect itself from cancer.
Normally, the p53 gene is a "tumour suppressor", telling cells with cancerous or pre-cancerous changes to self-destruct before they can thrive.
However, when it mutates, that ability is reduced or removed, making the appearance of cancer far more likely.
The researchers looked at frozen tumour tissue samples from a total of 246 women who underwent cancer treatment between 1997 and 2001.
Tests were carried out to determine the level of mutation in the p53 gene, and these were cross-referenced against the postcode where the woman lived, offering a rough snapshot of her background.
Women from deprived postcodes were more likely to have a p53 mutation, and were less likely to have survived cancer-free.
Dr Lee Baker, who led the study, said: "This research makes a strong link between p53 and deprivation, and then between p53 mutation and recurrence and death.
"As a social issue, it shows that if we lift people up the deprivation scale they will be less likely to have problems with their p53 gene, and go on to develop breast cancer."
He said that the way women lived could have a direct bearing on their p53 gene.
"Deprivation alone doesn't cause breast cancer, but can affect prognosis when p53 is damaged as a result of lifestyle choices commonly associated with deprivation."
Dr Caitlin Palframan, from Breakthrough Breast Cancer, said: "We know there is a connection between deprivation and breast cancer survival but we don't yet know all the reasons for this.
"The researchers suggest a genetic link between deprivation and survival, but a range of lifestyle, environmental and genetic factors are all likely to play a part."
She added: "Early detection of breast cancer is vital to increase the chance of successful treatment. That is why we encourage all women to be breast aware and attend screening when invited."