Defective genes increase breast cancer risk in young women to a greater extent than previously estimated

A joint study between St Mary’s Hospital, the Paterson Institute, Christie Hospital, The University of Manchester, Guys Hospital in London, and Cambridge University researching breast cancer has found that women with defects in certain genes have a higher chance of developing breast cancer when they are young than previous estimates. The report calls for more family history information to be taken from young women with breast cancer.

Breast cancer affects one woman in 10 to 12 in the UK, and about 5% of cases are due to strong hereditary factors. It was previously estimated that defects in one of a few genes were responsible for around 50% of the inherited breast cancers. The study says that mutations in one of three genes – BRCA1, BRCA2 and TP53 – could be responsible for about 60% of the inherited breast cancers.

It is the first study of it’s kind to look at the presence of all mutations in these three genes in women, and in such a large number of young women.

Ninety-nine women with breast cancer under the age of 30 took part in the study. One-third of the young women had a family history of breast cancer. Experts looked at the DNA of all the women to see whether they had mutations in one of three genes associated with breast cancer – BRCA1, BRCA2 and TP53. Forty seven per cent of the women with a family history of breast cancer had a mutation in one of these three genes. Of the women with no family history, one had a BRCA2 mutation (1.6%) and two a TP53 mutation (3%). This clearly shows that a family history of cancer indicates that the patient is likely to have a defective gene.

Strikingly, in fifty five per cent of cases where the women had a family history, there was no description of such a history in the hospital notes. This study stresses the need to make sure that details of other cancers in the family are recorded.

Professor Gareth Evans, Consultant Geneticist at St Mary’s Hospital and the Christie Hospital in Manchester said: “Among young breast cancer patients the recording of family history is frequently inadequate. This study demonstrates the importance of accurately recording a family history including the paternal side.

“We are recommending that all breast cancer notes carry a section on family history that has to be completed. With better recording of we can predict the majority young women carrying mutation genes, and as a result can alter how we clinically manage these patients. For example women with TP53 mutations are highly radiation-sensitive. As a consequence their diagnoses and treatment may be changed.

“As well as being able to identify and monitor susceptible women, it’s important for us to educate and counsel women about genetic information and cancer risk.”

Genes are important in regulating growth and repairing the DNA in cells. A faulty gene can deprive a cell of the crucial brakes needed to stop the controlled division typically found in cancer. Women with the gene can already be given more frequent mammograms to check for breast cancer. They may even have healthy tissue removed as a preventative measure. It is important to stress that not every woman with an altered gene will develop breast cancer.”