Exact Sciences

The study said that Cologuard was an "inefficient screening option" for colorectal cancer given its cost as compared to other CRC screening methods.

Of the 27 companies in the index, 12 firms' share prices retreated last month, 14 companies' stocks increased, and one firm's share value was flat.

The company's total revenues were $114.1 million compared with $95.6 million in the same quarter last year, beating analysts' expectations.

Exact said it will pay $72 per share for Genomic Health for a total transaction price of $2.8 billion in cash and stock.

Overall, the share prices for 18 of the index's 27 companies fell month over month. Exact Sciences was the only firm whose share price improved in the double digits.