Under the deal, biotech leader Roche will buy Flatiron for $1.9 billion (1.6 billion euros), according to a statement from the Swiss group, which already owns 12.6 percent of the US company.
Based in New York and with an office in San Francisco, Flatiron says it runs a huge platform with over two million patient records available for research by specialists, with over 2,500 oncology practitioners who use its data.
The platform is designed to allow cancer experts to come up with more personalised treatments for their patients.
The group's founders, Nat Turner and Zach Weinberg, created Flatiron after Google bought their previous company.
"Nat and Zach started Flatiron in pursuit of an audacious idea: combine some of the best minds in medicine and technology to transform the way cancer is understood and treated," according to Flatiron's website.
Following the acquisition, Flatiron will remain a separate legal entity to Roche, the Swiss group said.
"As oncology leaders in their respective fields, the acquisition allows both companies to accelerate progress towards data-driven personalized healthcare in cancer," Roche said.
Bloomberg in February reported that Roche also reached a deal earlier this year with General Electric Co. to develop software to "help oncologists make care decisions more quickly".
And it also recently reached acquisition deals for two other technology upstarts.