ATM is a gene that was first studied because of the recessive disorder, Ataxia-Telangiectasia (A-T). It was found that a higher amount of mothers of children with A-T were being diagnosed with breast cancer. Since these women were obligate carriers of an ATM mutation, meaning they had to have carried a mutation to have a child with A-T, scientists started investigating the link between ATM mutation carriers and breast cancer.
It has been suggested that women who carry a mutation in the ATM gene have an estimated 20-60% increased risk for breast cancer. Those with an ATM gene mutation are thought to be at increased risk for early-onset breast cancer and bilateral breast cancer. However, the exact breast cancer risk, and whether or not there is any other cancer risk, conferred by carrying a mutation in the ATM has not been determined. Some studies have also suggested a possible increased risk of sensitivity to radiation. Research in this area is ongoing and our understanding of the implications of carrying a single ATM mutation may change in the future. It is important for patients to keep in contact with their doctors and genetics providers for updates in this area.
The ATM gene is typically associated with an autosomal recessive condition called ataxia-telangiectasia (AT). AT is characterized by early onset cerebellar ataxia (lack of muscle coordination), telangiectases (dilated blood vessels) in the whites of the eyes, immune defects, and a predisposition to certain cancers, particularly leukemia and lymphoma. For an individual to have AT, he/she would have inherited a changed, or mutated, copy of the ATM gene from both parents. This means that each parent of a child with AT is a carrier of an ATM mutation. It is important to note that carriers are not at an increased risk for developing the neurologic features of AT but do have an increased risk for breast cancer.
Below is a screenshot of the table from the NCCN Guidelines showing the recommendations for ATM screening for individuals with at ATM mutation.
National Cancer Institute: Genetics of Breast and Ovarian Cancer http://www.cancer.gov/cancertopics/pdq/genetics/breast-and-ovarian/HealthProfessional/page3
Genetics Home Reference http://ghr.nlm.nih.gov/gene/ATM
(Renwick et al Nature Genetics. 2006; 38(8):873-875)
(Broeks et al Breast Cancer Res Treat. 2008; 107:243–248)