The bets on liquid biopsy keep getting bigger. Last month, Silicon Valley unicorn Grail Inc. raised a third round of financing to develop its blood-based tests for early cancer detection. That brings its total up to $1.5 billion since 2016, putting it among the top three most heavily funded private biotech companies in the US. While investors might be bullish on the risky venture, many oncologists have been more skeptical about how well Grail’s technique might work.

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