Breast cancer is the most frequently diagnosed cancer in women, accounting for over 15% of all new cancer cases in the United States. Abnormal cell growth in the breast ducts (DCIS) or lobules (LCIS) can sometimes progress to breast cancer, but currently, doctors cannot predict which cases will develop into invasive cancer.A recent retrospective study using the 313-SNP breast cancer polygenic risk score (PRS313) blood test suggests that women with abnormal cells are more likely to be diagnosed with breast cancer later on. This discovery could help identify patients who would benefit from targeted interventions while reducing unnecessary treatments. Although DCIS and LCIS can progress to breast cancer, predicting which cases will remain harmless has been a challenge. However, this new study indicates that calculating a polygenic score may help forecast a future breast cancer diagnosis.“It is therefore very important that we find ways to predict which women with DCIS and LCIS are most likely to develop invasive breast cancer in the future so they can be given the most appropriate treatment and avoid unnecessary treatment,” explained study senior author Elinor J. Sawyer of King’s College London (UK).What Is A Polygenic Score?A polygenic score is a numerical estimate of a person’s genetic likelihood of developing a particular trait or disease. When used to predict disease risk, it is often called a polygenic risk score (PRS), according to Harvard Medicine Magazine.Sawyer and study lead author Jasmine Timbres (King’s College London) focused on PRS313, a blood test that evaluates breast cancer risk by identifying which of 313 specific genetic variations (single nucleotide polymorphisms, or SNPs) a person carries. The researchers examined PRS313 scores from more than 2,000 DCIS and LCIS cases across the ICICLE and GLACIER studies.Their findings showed that, for DCIS, women with higher PRS313 scores were 2.03 times more likely to develop cancer in the opposite breast compared to those in the lowest score quartile. For LCIS, women with elevated PRS313 scores were 2.16 times more likely to develop cancer in the same breast. The risk was even higher for patients with a family history of breast cancer.“LCIS is not always treated with surgery or hormone therapy because it is considered lower risk than DCIS. However, these results suggest that women with a family history may benefit from additional interventions to reduce their risk of developing cancer,” Timbres added.How To Measure A Polygenic Score?A polygenic score is calculated by looking at an individual’s genetic variations (like SNPs) and summing them with weights based on how strongly each variant is associated with a trait or disease, as determined by large-scale genome-wide association studies (GWAS). Researchers first identify genetic variants linked to a disease by comparing the genomes of people with and without the condition. Each variant’s effect size is then applied to the individual’s genome to create a single score representing their overall genetic risk.Polygenic scores can be measured in research settings using GWAS data. They are also available through commercial direct-to-consumer genetic testing services or via clinical assessments provided by medical institutions and genetic counselors.Limitations Of The StudyWhile these findings are promising, further research is needed to confirm results in other patient groups and to examine additional genetic factors. Some limitations include the fact that PRS313 was designed specifically to assess risk for invasive breast cancer, meaning it may not capture other relevant genetic changes in in-situ breast disease. Additionally, the number of women with LCIS in the study was relatively small, which may have limited the ability to detect statistically significant associations.
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