U.S. FDA advisers back approval for Guardant's blood-based cancer test (May 23)

(This May 23 story has been corrected to say Shield is meant for CRC screening, not diagnosis, in paragraph 4, and fix a typo in paragraph 7.)

By Puyaan Singh and Leroy Leo

(Reuters) - Advisers to the U.S. Food and Drug Administration on Thursday recommended for the approval of Guardant Health's blood test to detect a cancer that begins in the colon or rectum.

The panel voted seven-to-two in favor of benefits outweighing risks when using the test called Shield for colorectal cancer (CRC).

The FDA is expected to decide whether it would approve Shield later this year, Guardant Health said.

If approved, Shield could become the second blood-based test for CRC screening in the United States after Epigenomics' Epi proColon, which was approved in 2016.

"The advisory committee's strong support for the approval of Shield reinforces the crucial role that a blood test option can have in improving CRC screening rates for those at average risk," Guardant co-CEO AmirAli Talasaz said.

CRC occurs in about 150,000 patients in the U.S. annually and is the second-leading cause of cancer fatalities in the country with more than 50,000 deaths each year, according to the FDA.

Currently, colonoscopy is considered the gold standard test for colon cancer, but adherence to it is low because it is invasive. Other tests include feces-related tests, such as Exact Sciences' Cologuard, but blood-based tests are considered more convenient.

Panelists raised concerns that Guardant's test was not as accurate as colonoscopy, especially as Shield detected only 13% of pre-cancerous tumors called advanced adenomas.

This was also flagged by FDA's staff reviewers in briefing documents released on Tuesday.

Guardant's application for Shield was based on a study that showed the test detected 83% of colorectal cancers, while Exact's Cologuard had 92.3% sensitivity rate, according to the FDA's documents.

Shield "is better than nothing but I don't want to downplay the issue that this test is going to miss a lot of cancers", said Charity Morgan, panel member and professor in the department of biostatistics at University of Alabama.

The company expects the test will need to be repeated every one to three years, Guardant Health executive Victoria Raymond said at the meeting, but added that "colonoscopy should be the prioritized option".

Trading in the shares of the company was halted on Thursday before the meeting started.

(Reporting by Puyaan Singh and Leroy Leo in Bengaluru; Editing by Arun Koyyur)