The family histories that patients give to their doctors are often not accurate, some cancer researchers report.

Family doctors commonly ask about family history to help base their recommendations for screening or referral to specialists. 

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Family cancer history might be a useful initial screening tool for doctors. (IStock)

To find out how accurate family histories are, Dr. Phuong Mai of the U.S. National Cancer Institute and colleagues surveyed 1,019 people in Connecticut about cancer diagnosis in first-degree relatives (parents, siblings and children) and second-degree relatives (grandparents, aunts, uncles, nieces and nephews.)

When the researchers tried to confirm cancer history for four common cancers in adults using information from state registries, Medicare, death certificates, health databases, and interviews directly with the relatives, they found the following rates of accuracy for the family histories provided by patients:

  • 61 per cent for breast cancer.
  • 27 per cent for colorectal cancer.
  • 32 per cent for prostate cancer.
  • 60 per cent or lung cancer.

"The results of this study suggest that family cancer history collected in the primary care setting might be useful as an initial screening tool, and, if positive, confirmation of the reported cancers is needed for the purpose of making cancer screening recommendations or referral to a specialty clinic," Mai and her co-authors concluded.

The findings highlight the limitations of relying on patient reports of family history to estimate risk, Dr. Rachel Freedman and Dr. Judy Garber of the Dana Farber Cancer Institute in Boston said in a journal editorial accompanying the study.

Mai's team went to "considerable effort to confirm cancer cases," the editorial noted.

Cancer patients may be more motivated to understand their family history in greater detail.

Value of online tools

Factors such as age and ethnicity might influence parents' knowledge of their family history, and cultural or generational differences affect how families discuss disease, Freedman and Garber said.

Smaller studies have shown limited awareness of intra-abdominal cancer such as pancreatic tumours, gynecological cancers, rare sarcomas or brain tumours in close relatives.

Despite better public awareness of the importance of family history through the media and the U.S. Surgeon General's 2004 declaration of Thanksgiving as National Family History Day to encourage families to gather and document health problems, this is just beginning, the editorial says.

A growing number of online family history tools — from one on the Surgeon General's site to genealogy websites to Facebook — may contribute to more accurate reporting, the pair said, but family history information should be regarded with "healthy skepticism."

"Although we should thoughtfully listen to our patients’ histories, we must listen even harder for what they 'could' be telling us, especially when specific information could influence their care and the care of their relatives," the editorial concluded.

The research was funded by the Intramural Research Program of the U.S. National Cancer Institute, U.S. National Institutes of Health and Westat, Inc.