After more than a year since the band's last concert, Megadeth returned as a live act in June 1997, beginning a world tour with the Misfits and touring in the United States with Life of Agony and Coal Chamber. In July, the band participated in Ozzfest '98 but, halfway through the tour, Menza reportedly discovered a tumor on his knee and left to undergo surgery. Jimmy DeGrasso, who had collaborated with Mustaine in MD.45, was hired to replace Menza for the remainder of the tour. Though initially meant to be a temporary replacement, DeGrasso joined the band permanently after the tour. Mustaine later said that he dismissed Menza from the band because he believed the drummer had lied about having cancer.