Women with the same breast cancer gene as Angelina Jolie could have a much higher chance of survival if they have a double mastectomy, evidence has suggested.
Over 20 more lives could be saved per 100 women if they opt to have both breasts removed rather than just one, it found.
The study, published in the British Medical Journal (BMJ) online, looked at women with faulty BRCA1 and BRCA2 genes - which cause a high risk of hereditary breast cancer - who had also been diagnosed with the earliest stages of the disease.
Hollywood star Jolie underwent a double mastectomy as a preventative measure to cut her risk of developing breast cancer in the future.
At present, NHS guidelines state that double mastectomies are just one option for women with a BRCA mutation.
Women with faulty BRCA genes have a 45% to 90% lifetime risk of developing breast cancer and also have a higher risk of ovarian cancer.
The researchers, from the United States and Canada, said a double mastectomy should be discussed as an option for young women with a BRCA mutation and early onset breast cancer.
However, they called for further studies given the small number of women in this group.
The study included 390 women from 290 different families with early-stage breast cancer, diagnosed between 1975 and 2009.
The women were either known carriers of faulty BRCA1 or BRCA2 genes, or were likely to be carriers, and underwent either a single or double mastectomy.
Some 44 women had a double mastectomy while 346 had a single mastectomy.
Of those who had a single mastectomy, 137 went on to have the other breast removed at a later date.
Over a 20-year follow-up period, 79 women died of breast cancer. This included 18 of those who had a double mastectomy and 61 who had a single breast removed.
Results showed that having both breasts removed was associated with a significant (48%) reduction in the risk of dying from breast cancer compared with only having one breast removed.
The researchers predicted that, of 100 women treated with double mastectomy, 87 would be alive after 20 years compared to 66 out of 100 in the other group.
They concluded it was "reasonable to propose bilateral mastectomy as the initial treatment option for a woman with early-stage breast cancer who carries a BRCA1 or BRCA2 mutation."
Martin Ledwick, head information nurse at Cancer Research UK, said: "The choices that women face when diagnosed with breast cancer, who are also found to be carriers of a BRCA1 or BRCA2 gene fault, are very difficult.
"It's important that all women in this situation have support and information to help them decide what to do. And this study highlights the need for further research in this area so that women have the best possible advice about the pros and cons of having a double mastectomy."
Emma Pennery, clinical director at Breast Cancer Care, said: "We know these women face life-changing decisions about cancer treatment while also coping with the implications of ongoing increased risk for both themselves and their families.
"Such decisions will mean weighing up the potential impact of mastectomy on body image and sexuality with relieving the anxiety about developing a new breast cancer.
"It's crucial that they have access to expert support and information about the likely prognosis of their breast cancer, their risk of developing breast cancer in the other breast and options for reconstruction, if they are to make informed decisions about their care."