Australasian Science: Australia's authority on science since 1938

Evidence for Family Cancer Syndromes

By Stephen Luntz

A study of women diagnosed with cancer before the age of 35 has found that their close relatives have double the risk of cancer for the general population.

The findings held true even after women with the BRCA1 and BRCA2 breast cancer gene mutations were removed as these mutations are already associated with family histories of ovarian and prostate cancer, respectively.

“The results suggest there could possibly be undiscovered genes causing breast cancer in these young women, and perhaps other cancers in their families,” says Prof John Hopper, Director of Research from the Centre for Molecular, Environmental, Genetic and Analytic Epidemiology at the University of Melbourne.

Hopper admits that the results are surprising and “no one believes it,” and adds that further studies are needed for confirmation. Nevertheless he describes the finding for the overall increased risk of cancer as “fairly robust”.

The data suggest a fivefold increased risk of prostate cancer for fathers and brothers and an eightfold increased risk of lung cancer for non-smoking close relatives. However, Hopper says that the sample size is too small to place much confidence is this. Breast and prostate cancers are considered to be similar, so the link there is less surprising than one for lung cancer. Brain cancers also showed a threefold increased risk.

Hopper says that early onset breast cancer was studied because “we had a data set from three countries, and genetic factors are thought to be more important in younger cases”.

Although environmental factors cannot be ruled out, Hopper says that “the only thing that is known to pre-dispose to lots of cancers is obesity,” and he doubts that was important in this sample.

“Cancer syndromes have been found through clinicians observing families,” Hopper says. “If this is confirmed it is the first time we will have found one through the data.”

Hopper is cautious as to whether family members of women with early diagnosis breast cancer should be screened, noting that MRI scans may be effective but also expensive. “Scans are available for family members with certain criteria, and maybe we should expand those. People need to be aware of their family history of different diseases. Who knows what could be significant?”