Mapping the genomes of breast tumors of individual patients, researchers discovered a world of vast variability, which can explain why the advancement of new treatments can prove difficult.

In a novel study, researchers from Washington University in St. Louis compared the full sequences of breast tumors of 50 patients with those patients’ DNA from normal cells. Through this method they were able to spot mutations, which can lead to cancer.

The findings were extraordinarily diverse. From the genetic sequences of just 50 tumors, the researchers discovered more than 1,700 mutations, and the majority of the mutations, they found, are specific to individual patients. This diversity can make widespread treatments difficult because they would prove ineffective in patients without the same genetic discrepancies.

However, the authors note that genomic information is vital to creating a personalized treatment plan. And further, the more scientists understand about similar mutations, the easier it will be to develop treatment interventions.

The study is scheduled to be presented at the annual American Association for Cancer Research meeting in Florida.