A family history of cancer increases the risk for other members of the family developing not only the same cancer (known as concordant cancer) but also a different (discordant) cancer, according to a large study of 23,000 people in Italy and Switzerland.

The research provides a comprehensive picture of the risk for developing various different types of cancer in families where there is a history of the disease. This is one of the few large studies of this kind that takes into account other important factors, such as individual characteristics and lifestyles, which could also affect the degree of risk. The study was published in Annals of Oncology (2013; doi:10.1093/annonc/mdt280).

Results from the study supported known associations, such as the increased risk for developing the same cancer as a close relative, and the 1.5-fold increased risk for breast cancer in women with a history of colorectal cancer in the family.

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However, the study also found a 3.3-fold increased risk for developing oral and pharyngeal cancer among people who had a first-degree relative with cancer of the larynx, and a 4-fold increased risk of cancer of the esophagus where a first-degree relative had oral or pharyngeal cancer. If a first-degree relative had breast cancer, female family members had a 2.3-fold increased risk for ovarian cancer. Family members had a 3.4-fold increased risk for prostate cancer if a first-degree relative had bladder cancer.

The researchers from Italy, Switzerland, and France looked at 12,000 cases of cancer occurring in 13 different cancer sites (mouth and pharynx, nasopharynx, esophagus, stomach, colorectum, liver, pancreas, larynx, breast, uterus, ovaries, prostate, and kidneys) between 1991 and 2009. They matched them with 11,000 people without cancer, and collected information on any cancer in the family, particularly in a first-degree relative, age at diagnosis, sociodemographic characteristics, body shape, lifestyle habits such as smoking and alcohol intake, diet, personal medical history (including menstrual and reproductive factors, and use of oral contraceptives), and hormone replacement therapy.

“Besides confirming and quantifying the well-known excess risks for people developing the same cancer as their first-degree relative, we have identified increased risks for developing a number of different cancers. We have also found that if a patient was diagnosed with certain cancers when they were younger than 60 years, the risks of a discordant cancer developing in family members were greater,” said research team member Eva Negri, PhD, head of the Laboratory of Epidemiologic Methods at the Mario Negri Institute for Pharmacological Research in Milan, Italy.

Negri added, “A major strength of our study is that we were able to adjust our analyses for tobacco, alcohol and a number of other lifestyle habits, which most previous studies have not been able to do.”