Aug. 11 (Bloomberg) -- Former U.S. Senate Majority Leader George Mitchell, who has been leading an independent probe of steroid use among Major League Baseball players, was diagnosed with prostate cancer.

``The cancer is small, low grade and localized, and can be effectively treated and cured,'' Harvey Klein, Mitchell's physician, said in a statement released by Mitchell's law firm, DLA Piper US LLP. ``The prognosis is very good.''

The treatment won't affect the investigation of performance enhancing substances by baseball players, Mitchell, 73, said in the statement.

``The investigation, which is in its final phases, will be completed in the coming months and neither the substance nor the timing of the report will be affected in any way,'' said Mitchell, a Democrat from Maine.

Mitchell, who was appointed to investigate steroids by MLB Commissioner Bud Selig in March 2006, said in June that hundreds of people have been interviewed and thousands of documents have been reviewed during the 18-month inquiry.

To contact the reporter on this story: Nancy Kercheval in Washington at nkercheval@bloomberg.net.

Last Updated: August 11, 2007 13:03 EDT