The intronic G13964C variant in p53 is not a high-risk mutation in familial breast cancer in Australia

Background: Mutations in BRCA1 and BRCA2 account for approximately 50% of b reast cancer families with more than four affected cases, whereas exonic mu tations in p53, PTEN, CHK2 and ATM may account for a very small proportion. It was recently reported that an intronic variant of p53 - G13964C - occur red in three out of 42 (7.1%) 'hereditary' breast cancer patients, but not in any of 171 'sporadic' breast cancer control individuals (P = 0.0003). If this relatively frequent occurrence of G13964C in familial breast cancer a nd absence in control individuals were confirmed, then this would suggest t hat the G13964C variant plays a role in breast cancer susceptibility. Method: We genotyped 71 familial breast cancer patients and 143 control ind ividuals for the G13964C variant using polymerase chain reaction (PCR)- res triction fragment length polymorphism (RFLP) analysis. Results: Three (4.2%; 95% confidence interval [CI] 0-8.9%) G13964C heterozy gotes were identified. The variant was also identified in 5 out of 143 (3.5 %; 95% CI 0.6-6.4%) control individuals without breast cancer or a family h istory of breast cancer, however, which is no different to the proportion f ound in familial cases (P = 0.9). Conclusion: The present study would have had 80% power to detect an odds ra tio of 4.4, and we therefore conclude that the G13946C polymorphism is not a 'high-risk' mutation for familial breast cancer.