A family history of breast and ovarian cancer from both parents matters. (iStock)

A father's family history of breast and ovarian cancer may be overlooked by both patients and doctors, a study suggests.

Women with female relatives who've had breast and ovarian cancer are often aware of their increased risk and seek genetic counselling but the father's family history may be neglected.

Men and women have the same 50 per cent risk of passing on mutations in the BRCA1 or BRCA2 tumour suppressor genes, which increase lifetime risk for breast and ovarian cancers.

Health-care providers may be "unaware that these women might have inherited the mutated gene from their father …and might not routinely collect this information from their patients," genetic counsellor Jeanna McCuaig from Toronto's Princess Margaret Hospital and her co-authors in Toronto and Montreal wrote in commentary in the journal The Lancet Oncology.

Since many women don't recognize a paternal family history of the cancers as a risk factor for the diseases, they are unlikely to volunteer the information unless directly questioned about it, the researchers said.

Concerned about the potential missed opportunity, the authors reviewed patient charts at their family breast and ovarian cancer clinic.

The researchers determined patients were five times more likely to be referred with a paternal, rather than a maternal, family history of breast or ovarian cancer.

Anecdotal cases

The chart reviewed justified the assumption but did not offer a concrete explanation for why they exist or how to remedy it, the authors said.

Anecdotally, the authors wrote that they knew of two patients — a man with a substantial family history of breast and ovarian cancer, and a woman with a known BRCA2 mutation in her father's family — who were both falsely reassured by their health-care providers that the history did not increase their or their daughters' cancer risks.

"The patients were not offered genetic assessment and testing or the appropriate medical options," the paper said. "The man subsequently came to our attention when a BRCA1 mutation was detected in his family member; the woman when she sought genetic testing after she was diagnosed with breast cancer."

The researchers suggested that health-care providers should be familiar with general trends in hereditary cancers, including:

• Diagnosis at younger ages than sporadic cancers.
• Diagnosis with many primary cancers.
• Several family members over generations might be diagnosed with cancer, particularly rare forms or breast and ovarian cancer.
• Higher risk among certain ethnic groups, such as a greater likelihood of inheriting the BRCA1 or BRCA2 gene mutations among those of Ashkenazi Jewish descent.

According to the study, about 20 per cent to 30 per cent of the more than 690,000 women diagnosed with breast cancer and nearly 190,000 diagnosed with ovarian cancer in developed countries have a family history of cancer.

The BRCA1 and BRCA2 mutations are linked to aggressive hereditary breast cancers, but only account for about 15 per cent of all cases.