For years, the American Society of Clinical Oncology gave research data early to members in an embargoed book of abstracts, or summaries, that weren’t supposed to be made public until the yearly meeting began. But inevitably, the findings leaked, and the resulting insider trading caused biotech shares to fluctuate as much as 10 percent, the so-called ASCO effect, Bloomberg News writes.

The rules have changed this year, and study data will be released all at once to doctors, media and investors tonight at 9 pm EST. This means securities analysts, fund managers and others will be up all night, sorting through an unprecedented torrent of almost 5,000 studies on new cancer treatments, looking for market-moving data.

“There is always some make-or-break data with these one- product companies that leads to an explosion,” Dave Heupel, who manages $60 billion at Thrivent Financial for Lutherans, tells Bloomberg. “There are always going to be people attempting to get the data before everyone else can. It is part of what you have to endure year in and year out.”

Abstract books are bound volumes that contain summaries of each study that will be presented at a medical meeting, boiled down to about a dozen sentences. The books don’t put the findings into perspective or compare different trials, leaving room for interpretation, Bloomberg writes, adding that, in ASCO’s case, the abstract book is expected to contain information on about 4,850 studies.

Scientific info, of course, equals big business in the $41 billion cancer market, and Michael King of Rodman & Renshaw says having a fair shot at the data is a welcome change. “The way they were doing it before was absurd and quite unfair,” King, tells Bloomberg. “Although it’s a pain, putting it out on the Web for everyone to see is the best way to do it. I only wish it had been done years ago.”