ATM mutations in female breast cancer patients predict for an increase in radiation-induced late effects.
OBJECTIVE
Mutation of the ATM gene may be associated with enhanced radiosensitivity and increased radiation-induced morbidity. Denaturing high performance liquid chromatography (DHPLC) is a powerful new technique proven to be sensitive and accurate in the detection of missense mutations, as well as small deletions and insertions. We screened female breast cancer patients for evidence of ATM gene alterations using DHPLC. This study attempted to determine whether breast cancer patients who develop severe radiotherapy (RT)-induced effects are more likely to possess ATM mutations than patients who display normal radiation responses.


METHODS
Forty-six patients with early-stage breast carcinoma underwent limited surgery and adjuvant RT. DNA was isolated from blood lymphocytes, and each coding exon of the ATM gene was amplified using polymerase chain reaction. Genetic variants were identified using DHPLC by comparing test patterns with a known wild-type pattern. All variants were subjected to DNA sequencing and compared with wild-type sequences for evidence of a mutation. A retrospective review was performed, and the Radiation Therapy Oncology Group/European Organization for Research and Treatment of Cancer acute and late morbidity scoring schemes for skin and subcutaneous normal tissues were applied to quantify the radiation-induced effects.


RESULTS
Nine ATM mutations were identified in 6 patients (8 novel and 1 rare). The median follow-up was 3.2 years (range 1.3-10.3). A significant correlation between ATM mutation status and the development of Grade 3-4 subcutaneous late effects was found. All 3 of the patients (100%) who manifested Grade 3-4 subcutaneous late sequelae possessed ATM mutations, whereas only 3 (7%) of the 43 patients who did not develop this form of severe toxicity harbored an ATM mutation (p = 0.001). One ATM mutation carrier developed Grade 4 soft tissue necrosis after RT and required hyperbaric oxygen. All 3 patients manifesting Grade 3-4 late subcutaneous responses in fact harbored 2 ATM mutations. In contrast, none of the 3 ATM carriers who had a single mutation developed a severe subcutaneous reaction. ATM mutation status did not predict for a significant increase in early effects. Of the 23 patients with Grade 2-3 moist desquamation, 4 (17%) had an ATM mutation compared with 2 (9%) of 23 patients without desquamation (p = 0.7).


CONCLUSIONS
Possession of an ATM mutation, particularly when 2 are present, may be predictive of an increase in subcutaneous late tissue effects after RT for breast cancer and may subsequently prove to be a relative contraindication to standard management. These patients may be better served with reduced doses of radiation. Equivalent local control remains to be tested, but this germline alteration may radiosensitize normal tissues, as well as the tumor itself. DHPLC is effective in the identification of these patients. A larger study is required to confirm these findings.
Iannuzzi
Christopher M
CM
Department of Radiation Oncology, Mount Sinai School of Medicine, New York, NY 10029, USA. christopher.iannuzzi@mountsinai.org
Atencio
David P
DP
Green
Sheryl
S
Stock
Richard G
RG
Rosenstein
Barry S
BS
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D064007:Ataxia Telangiectasia Mutated Proteins; D001943:Breast Neoplasms / Q000235:genetics* / Q000473:pathology / Q000532:radiotherapy*; D018797:Cell Cycle Proteins; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D004268:DNA-Binding Proteins; D005260:Female; D006801:Humans; D008875:Middle Aged; D009154:Mutation; D009367:Neoplasm Staging; D017346:Protein Serine-Threonine Kinases / Q000235:genetics*; D011836:Radiation Tolerance / Q000235:genetics*; D011855:Radiodermatitis / Q000235:genetics* / Q000473:pathology; D012189:Retrospective Studies; D025521:Tumor Suppressor Proteins
D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D025521:Tumor Suppressor Proteins; C576324:ATM protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; D017346:Protein Serine-Threonine Kinases