People with a family history of cancer have an increased risk of developing not only the same cancer, but also a different form of the disease, according to a study published in the journal Annals of Oncology.

Researchers from Italy, Switzerland and France analyzed 12,000 cases of cancer occurring in 13 different sites of the body between 1991 and 2009. These were compared with 11,000 people without cancer.

Information on any cancer in the family, particularly in first-degree relatives (directly related), was collected in both groups. Other details collected included:

  • Age of diagnosis
  • Body shape
  • Lifestyle habits, including smoking and alcohol intake
  • Sociodemographic characteristics
  • Diet
  • Personal medical history
  • Use of oral contraceptives and hormone replacement therapy

The researchers say that the results of the study confirmed links already known, like the increased risk of developing the same cancer as a close relative.

But the researchers also say that the most interesting results of the study revealed that family members who had relatives with a specific form of cancer were also at higher risk of developing a different form of the disease.

The results revealed:

  • Family members who had a first-degree relative with cancer of the larynx were 3.3 times more likely to develop oral and pharyngeal cancer
  • Family members who had first-degree relative with with oral or pharyngeal cancer were 4 times more likely to develop oesophageal cancer
  • Female family members who had a first-degree relative who suffered from breast cancer were 2.3 times more likely to develop ovarian cancer
  • Family members who had a first-degree relative who had bladder cancer were 3.4 times more likely to develop prostate cancer.

Dr. Eva Negri, head of the Laboratory of Epidemiologic Methods at the Mario Negri Institute for Pharmacological Research, Milan, Italy, says of the results:

“Besides confirming and quantifying the well-known excess risks of 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, the risks of a discordant cancer developing in family members were greater.”

Dr. Negri adds that because this study analyzed a large number of people, this revealed links in some rare forms of cancer.

She adds:

“For some rare cancers, a weak association with a different, common cancer can, on a population level, reveal a higher attributable risk than a strong association with the risk of developing the same cancer. For example, for ovarian cancer we found that a family history of breast cancer had a stronger attributable risk of ovarian cancer than the far rarer, albeit stronger, association with family history of ovarian cancer.”

The researchers say that some of the results of this study could be due to shared habits among family members, such as smoking or drinking. But she adds that the results show there are many cancer syndromes appearing among close relatives that show how the presence of genetic factors could influence the development of cancer in multiple sites of the body.

Dr Negri says:

“These findings may help researchers and clinicians to focus on the identification of additional genetic causes of selected cancers and on optimizing screening and diagnosis, particularly in people with a family history of cancer at a young age.”