Severe reaction to radiotherapy for breast cancer as the presenting feature of ataxia telangiectasia

BACKGROUND: Severe early and late radiation reaction to radiotherapy is extremely rare in breast cancer patients. Such a reaction prompted an investigation into a 44-year-old mother (patient A-T213). METHODS: A neurological examination was performed and blood lymphocytes and skin fibroblasts were assessed for radiosensitivity chromosomally and by colony-forming assay. The ATM gene was sequenced and ATM mutations modelled by site-directed mutagenesis. The ATM kinase activity was also assessed. RESULTS: Patient A-T213 was normally ambulant with no ataxia and minimal other neurological features. T lymphocytes and skin fibroblasts were unusually radiosensitive, although less sensitive than in classical ataxia telangiectasia (A-T). A lymphoblastoid cell line and skin fibroblasts expressed ATM protein with some retained kinase activity. One missense ATM mutation c.8672G>A (p.Gly2891Asp) and a c.1A>G substitution were identified. In the modelling system the p.Gly2891Asp mutant protein was expressed and shown to have residual ATM kinase activity. CONCLUSION: Patient A-T213 has a milder form of A-T with biallelic ATM mutations, which may have contributed to breast cancer development, and certainly caused the severe radiation reaction. Ataxia telangiectasia should be investigated as a potential cause of untoward severe early and late radiation reactions in breast cancer patients. British Journal of Cancer (2012) 106, 262-268. doi:10.1038/bjc.2011.534 www.bjcancer.com Published online 6 December 2011 (C) 2012 Cancer Research UK