UPDATE 2-US lawmakers seek answers on Vytorin cancer report

(Adds comment from companies; updates shares)

WASHINGTON, Sept 2 (Reuters) - Two U.S. congressmen asked Merck & Co (MRK.N) and Schering-Plough Corp SGP.N for more information on a report the companies submitted to regulators assessing a possible link between cholesterol drug Vytorin and cancer, a letter released on Tuesday said.

Democratic Reps. John Dingell and Bart Stupak wrote they "were somewhat surprised to discover that the report contains little more than the information that was presented at the July 21, 2008, press conference" about the findings.

They asked the companies when the report was prepared, whether it represented all the information submitted to the Food and Drug Administration and why it was not made public.

The letter comes as researchers in Munich earlier on Tuesday released fuller data from company-sponsored clinical trials that showed more patients given the combination pill were diagnosed with cancer compared with those given a sugar pill. (For story, click on [ID:nL2495534])

Out of 1,873 patients, results showed 105 cancer cases among Vytorin patients compared with 70 taking a placebo, up from 93 and 65 reported previously in July.

Company officials have maintained the increase is due to chance.

Last month, the two Michigan lawmakers questioned those claims in a separate letter to the companies requesting roughly 10 years worth of related documents and expressing concern that the report, compiled by an Oxford University researcher, was not independent as claimed.

Richard Peto, a cancer epidemiologist who conducted the Oxford analysis, told Reuters in Munich that Dingell's committee action last month amounted to "harassment," adding it was clear there was no credible evidence of a cancer link.

In the latest letter made public on Tuesday, the lawmakers questioned whether the companies or anyone else had tampered with the report before sending it to the FDA as well as whether Peto had conducted any other analyses. It also asked the companies to allow congressional staffers to interview Peto.

Merck and Schering-Plough said in a statement they would cooperate with the committee's investigation.

The companies also said Peto's report was prepared "independently" and they knew of no other reports sent by his research group to the FDA.

Shares of Merck fell 2.3 percent to close at $34.83 while Schering-Plough shares dropped 1.6 percent to $19.09, both on the New York Stock Exchange. (Reporting by Lisa Richwine and Susan Heavey in Washington and Ben Hirschler in Munich; editing by Gerald E. McCormick and Braden Reddall)