The American Society of Clinical Oncology meeting, the year's biggest event for cancer research—and for the investors that bet on its outcomes—takes place May 30 to June 3 in Chicago. However, much of the buzz around the meeting comes out in advance, in what's known as the ASCO abstract drop.
The event generally leads to a flurry of stock moves among volatile biotech companies the next day. Yet this year, analysts say, big pharma companies will dominate the show.
Following the release, Clovis Oncology stock rose on results of early stage lung cancer drug study while Incyte stock fell after the close following results on its pancreatic cancer drug were deemed not statistically significant.
One major focus of the conference will be on a type of drugs called immunotherapy, which harness the immune system to fight cancer.
Bristol-Myers Squibb, Merck, AstraZeneca, Roche and others will all have data on immuno-oncology drugs. AbbVie, Eli Lilly, and Johnson & Johnson, said Mark Schoenebaum of ISI Group, are also worth watching for data on their cancer drugs.
So why are big pharmas dominating the show this year? For at least four of them, Schoenebaum pointed out, it's because they acquired their drugs from biotechs:
"Another piece of evidence that the skills needed to successfully invest in pharma are basically the same as biotech," Schoenebaum wrote in a note to clients Wednesday.
Still, some biotechs are on watchlists heading into ASCO.
Ian Somaiya at Nomura Securities is looking at Incyte and Pharmacyclics, whose data, he said, may "have a meaningful impact on shares."
He's concerned an Incyte drug, known as an IDO1 inhibitor, may disappoint in a combination with Bristol-Myers' Yervoy, and warns of "misplaced investor fear" that a trial from AbbVie could present greater competition to Pharmacyclics' leukemia drug Imbruvica.
Both, Somaiya said, could represent buying opportunities.
"Volatility around ASCO abstracts could provide an attractive entry point for Incyte and Pharmacyclics," he wrote in a research note Monday, "as meeting presentations should drive upside heading into" the second half of the year.
—By CNBC's Meg Tirrell.