Updated

Quest Diagnostics Inc on Tuesday became the largest U.S. company to start offering gene-based tests for inherited forms of breast cancer since the U.S. Supreme Court ended Myriad Genetics Inc's monopoly on the tests for specific gene mutations.

Quest, the largest U.S. medical testing company by revenue, said its BRCAvantage tests will search for mutations in the BRCA1 and BRCA2 genes, which dramatically increase a woman's risk of developing breast and ovarian cancers.

After a long legal battle, the U.S. Supreme Court in June ruled that naturally occurring human genes could not be patented, effectively ending Myriad's stranglehold on the market for BRCA testing.

Myriad's BRCA tests gained worldwide attention earlier this year when Oscar-winning actress Angelina Jolie publicly announced she had undergone a double mastectomy after learning through the Myriad test that she carried the gene mutations and an 87 percent risk of developing breast cancer without the preemptive surgery.

Breast cancer kills about 458,000 people each year, according to the World Health Organization. It estimated that one in 300 to one in 500 women carry the BRCA1 or BRCA2 gene mutation. An estimated five percent to 10 percent of female breast cancers are associated with inherited gene mutations with the BRCA1 and BRCA2 mutations the most commonly identified cause, Quest said.

Despite the vast publicity surrounding Jolie's announcement and the subsequent Supreme Court ruling, a national survey of 1,460 U.S. women aged 18 and older conducted for Quest found 72 percent of respondents had never heard of the BRCA test.

Fifty eight percent said they would want to know if they carried the high-risk gene mutations, yet only 17 percent of those who said they were familiar with BRCA testing had discussed it with a healthcare provider, according to the survey conducted this month by Harris Interactive.

The size of Quest could help spread awareness along with availability of the genetic testing. The Quest BRCA tests are now available in 49 states and awaiting a state review in New York, where it is expected to be available later this year, the company said.

Quest has more than 2,100 centers in the United States at which patients can submit blood samples for genetic testing. The cost of the test is about $2,500, a drop from the $3,000 to $4,000 Myriad had charged for its tests.

Quest said it believes the vast majority of women for whom BRCAvantage testing would be appropriate will have it covered under health insurance plans.

"Patients need to understand their cancer risks in order to make the most informed and timeliest decisions about their health," Jon Cohen, chief medical officer for Quest Diagnostics, said in a statement.