Having a faulty BRCA gene - either BRCA1 or BRCA2 - is known to increase a woman’s risk of breast cancer.
Women with the gene faults are advised to have regular screening for breast cancer and some, such as Angelina Jolie, choose to have preventative surgery, such as a double mastectomy, to limit their chances of breast cancer diagnosis.
But the study by the University of Southampton, of women between the ages of 18 and 40 years, found after treatment, there was no significant difference is survival rate between women who have a faulty gene and women who do not.
However, the researchers noted the results might not translate to older women with a BRCA mutation, as they were not involved in the study and more research would be needed in this area.
This is of particular note as the majority of breast cancer cases (81%) occur in women over the age of 50.
Faulty BRCA1 or BRCA2 genes are inherited and these mutations place women at a greater risk of breast and some ovarian cancers.
Past studies have suggested 45%-90% of women with the mutation develop breast cancer during their lifetime, compared to roughly 12.5% of women developing breast cancer in their lifetime overall in the UK.
The study recruited young women with breast cancer between the years 2000 and 2008, when BRCA testing and risk-reducing surgery were not routine for early breast cancer (stage one or stage two).
The researchers noted previous evidence on whether carrying these types of mutation affects a woman’s cancer prognosis has been mixed.
The study involved 127 hospitals across the UK and included 2,733 women aged 18-40 years who had recently been diagnosed with breast cancer for the first time.
All women included in the study were tested for BRCA mutations, and 338 (12% carried one – including 201 women with a mutation in the BRCA1 gene and 137 with a mutation in the BRCA2 gene.
The researchers tracked the women a their treatment for more than eight years.
The majority of women (89%) underwent chemotherapy. Half had breast-conserving surgery (49%), half had a mastectomy (50%), and less than 1% had no breast surgery.
During the course of the study, out of the 2,733 women, there were 678 deaths, including 651 deaths from breast cancer, 18 from other cancers, and nine from other causes.
The study found that there was no difference in overall survival two, five or 10 years after diagnosis for women with and without a BRCA mutation. These findings remained similar regardless of whether mutations were in the BRCA1 or BRCA2 gene.
Commenting on the findings, Professor Diana Eccles, head of cancer sciences at the University of Southampton, said: “Our study is the largest of its kind and our findings suggest that younger women with breast cancer who have a BRCA mutation have similar survival to women who do not carry the mutation after receiving treatment.
“Women diagnosed with early breast cancer who carry a BRCA mutation are often offered double mastectomies soon after their diagnosis or chemotherapy treatment, however, our findings suggest that this surgery does not have to be immediately undertaken along with the other treatment.
“In the longer term, risk-reducing surgery should be discussed as an option for BRCA1 mutation carriers in particular, to minimise their future risk of developing a new breast or ovarian cancer. Decisions about timing of additional surgery to reduce future cancer risks should take into account patient prognosis after their first cancer, and their personal preferences.”
Professor Peter Fasching, from Friedrich-Alexander University Erlangen-Nuremberg, Germany, added: “This important topic needs more prospective research as preventive surgical measures might have an effect on what might be a very long life after a diagnosis of breast cancer at a young age.”
The study is published in full in The Lancet Oncology journal.