Survivors of breast cancer are at significantly higher risk of developing second cancers, including endometrial and ovarian cancer for women and prostate cancer for men, University of Cambridge research has found.
The study of data from almost 600,000 patients in England has also shown, for the first time, that this risk is higher among people living in areas of greater socioeconomic deprivation.
Breast cancer is the most commonly diagnosed cancer in the UK, with around 56,000 people in the UK diagnosed each year - more than 99 per cent of whom are women.
With improvements in earlier diagnosis and treatments, five-year survival rates reached 87 per cent by 2017 in England.
Those who survive breast cancer are known to be at risk of second primary cancer, but the nature of that risk has been unclear until now, with previously published research suggesting women and men who survive breast cancer are at a 24 per cent and 27 per cent greater risk of a non-breast second primary cancer than the wider population respectively.
It has also been suggested that second primary cancer risks differ by the age at breast cancer diagnosis.
The University of Cambridge team set out to provide a more accurate picture by analysing data from more than 580,000 female and more than 3,500 male breast cancer survivors diagnosed between 1995 and 2019 using the National Cancer Registration Dataset.
First author Isaac Allen, from Cambridge’s Department of Public Health and Primary Care, said: “It’s important for us to understand to what extent having one type of cancer puts you at risk of a second cancer at a different site. The female and male breast cancer survivors whose data we studied were at increased risk of a number of second cancers. Knowing this can help inform conversations with their care teams to look out for signs of potential new cancers.”
Females who survived breast cancer were at double the risk of contralateral breast cancer - that is, in the unaffected breast - compared to the general population and at 87 per cent greater risk of endometrial cancer, 58 per cent greater risk of myeloid leukaemia and 25 per cent greater risk of ovarian cancer.
Females diagnosed with breast cancer under the age of 50 were 86 per cent more likely to develop a second primary cancer compared to the general population of the same age, whereas women diagnosed after age 50 were at a 17 per cent increased risk.
This may be because a larger number of younger breast cancer survivors may have inherited genetic alterations that increase risk for multiple cancers. Women with inherited changes to the BRCA1 and BRCA2 genes, for example, are at increased risk of contralateral breast cancer, ovarian and pancreatic cancer.
Females from the most socio-economically deprived backgrounds were found to be at 35 per cent greater risk of a second primary cancer compared to females from the least deprived backgrounds
This difference was primarily driven by non-breast cancer risks, such as lung, kidney, head and neck, bladder, oesophageal and stomach cancers, and may be because smoking, obesity, and alcohol consumption are more common among more deprived groups and area established risk factors for these cancers.
Isaac, a PhD student at Clare Hall, added: “This is further evidence of the health inequalities that people from more deprived backgrounds experience. We need to fully understand why they are at greater risk of second cancers so that we can intervene and reduce this risk.”
Male breast cancer survivors, meanwhile, were 55 times more likely than the general male population to develop contralateral breast cancer, although the risk was still very low. For every 100 men diagnosed with breast cancer at age 50 or over, about three developed contralateral breast cancer during a 25-year period. Male breast cancer survivors were also 58 per cent more likely than the general male population to develop prostate cancer.
Prof Antonis Antoniou, from Cambridge’s Department of Public Health and Primary Care at the University of Cambridge, the study’s senior author, said: “This is the largest study to date to look at the risk in breast cancer survivors of developing a second cancer. We were able to carry this out and calculate more accurate estimates because of the outstanding data sets available to researchers through the NHS.”
Cancer Research UK’s senior cancer intelligence manager, Katrina Brown, said: “This study shows us that the risk of second primary cancers is higher in people who have had breast cancer, and this can differ depending on someone’s socioeconomic background. But more research is needed to understand what is driving this difference and how to tackle these health inequalities.”
The research, published in Lancet Regional Health – Europe, was funded by Cancer Research UK with support from the National Institute for Health and Care Research Cambridge Biomedical Research Centre.
People who are concerned about their cancer risk should contact their GP for advice. If you or someone close to you have been affected by cancer and you’ve got questions, you can call Cancer Research UK nurses on freephone 0808 800 4040, Monday to Friday.
