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With this latest discovery, the genetic factors underpinning a verysignificant proportion of inherited risk of ER+ breast cancer have now beenelucidated. Common variants previously discovered by deCODE on chromosomes2q35 and 16q12 are together involved in an estimated 25% of ER+ breastcancers. The analysis in today's paper also reveals that a fourth known set ofvariants, located on chromosome 10q26 and accounting for approximately 16% ofbreast cancers, appear to confer risk exclusively of ER+ tumors. deCODE isapplying these variants as the basis for a DNA-based reference laboratoryrisk-assessment test the company plans to launch in the coming months. Such atest will allow for the identification of women who may benefit from regularscreening with standard as well as new, high-resolution technologies. TheAmerican Cancer Society now recommends that women who are at a 20-50% above-average risk of breast cancer should consider undergoing annual magnetic-resonance imaging (MRI) scans as well as mammograms.
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"Within the past two years we have identified specific sequence variantsthat underlie much of the inherited risk of the common forms of breast cancer,the most frequently diagnosed cancer in women. And we have now reached a longawaited tipping point in this progress: the ability to identify, through asimple genetic test, a large proportion of women who are at a clinically-meaningful risk of the disease. The rationale for such testing is all the morecompelling in ER+ cancers, since drugs such as tamoxifen have been shown to besuccessful in preventing as well as treating these cancers, and other drugsnow in development may prove to be safe as long-term prophylactic therapy aswell. deCODE's pioneering work in this field has also demonstrated that ER+and ER- breast cancer appear to have distinct genetic bases, a phenomenonwhich may open the way to a better understanding of the nature, treatment andprevention of breast cancer in general. One of the most pressing next steps inthis research is to analyze these results in large cohorts of women of non-European descent," said Kari Stefansson, CEO of deCODE.
deCODE made today's discovery through the analysis of genotypic data froma total of nearly 40,000 patients and control subjects from five countries.The deCODE team analyzed both genome-wide data on some 300,000 SNPs,supplemented by data on a much smaller number of SNPs on chromosome 5p12.
deCODE gratefully acknowledges the participation of the patients andresearchers who took part in this study.
About Breast Cancer
Breast cancer is the most common cancer and the second leading cause ofcancer deaths among women. Breast cancers are classified as ER+ or ER-according to whether tumors are found to contain estrogen receptors; in womenof European descent approximately three-quarters are ER+, and in women ofAfrican descent approximately 50% a
