Mastodon are very sorry to inform fans that their upcoming summer tour dates are all cancelled(June 5th Germany/ July 3rd Finland). These dates include the Sonisphere Festivals, which many fans greatly anticipate.
Guitarist Bill Kelleher was diagnosed with pancreatitis and doctors advice him to pursue further medication. However, they are optimistic and expect full recovery in the coming weeks for Bill, as the band would like to participate in the BlackDiamondSkye tour with Alice in Chains and Deftones, starting on September.
Source: gr.sonispherefestivals.com