More Genetic Effects on Breast Cancer Risk

Several tiny genetic differences can increase a woman’s risk of breast cancer, a study has found. Researchers tested the blood of 20,700 women. Half had breast cancer when the study began. The others did not. Researchers focused on the building blocks that form DNA. Sometimes one block is replaced by another. This is called a single-nucleotide polymorphism, or SNP. These often occur in the DNA between genes. Researchers found seven SNPs that had the biggest effect on breast cancer risk. Women were given a score based on how many of these they had. Women with the highest scores were twice as likely to have breast cancer as women with the lowest scores. The increase in risk was greatest for the most common type of breast cancer. This type grows in response to estrogen. The study appeared in the Journal of the American Medical Association. HealthDay News wrote about it July 27.