Actress Angelina Jolie's decision to get a jump on her genes and have a double mastectomy shows the importance of knowing your family history, according to one Ottawa doctor.

Jolie said in an op-ed in the New York Times she believed "faulty" genes that saw her mother die of cancer at age 55 meant she too had an 87 per cent chance of breast cancer. So she underwent a three-month process to remove her breasts that ended in April.

Dr. Mark Clemons of the Ottawa Cancer Centre, whose team tests people with breast cancer genes, said most women who undergo mastectomies based on genetics already have tumours.

However, he said there is a lesson to be learned from Jolie.

"Make sure you have a full family history. Find out about those relatives who have had cancer. How old were they and what sort of cancer was it?" he said.

"In those healthy people who have been found to have a genetic mutation that increases the risk of breast cancer, the risk can be as high as 87 per cent."

Ottawa's Darla Wilbond said she was diagnosed with breast cancer last fall and had a successful lumpectomy, but plans to get both her breasts removed.

"At my age, because I'm 65, I think to me it's OK and my husband supports any decision I make," she said.

"I think I'd rather have the long life and be a great grandmother."

Researchers at the Ottawa Cancer Centre said only five per cent of breast cancers are genetic, but the risk is significant when they do exist.