The reunited Black Sabbath was one of the planned headliners for this year's Coachella Valley Music and Arts Festival, but was forced to pull out just before yesterday's official lineup announcement due to guitarist Tony Iommi's recent lymphoma diagnosis, multiple industry sources tell Billboard.

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It's unclear which artist was added as a last-minute replacement for Coachella, which will be headlined by Radiohead, the Black Keys and Dr. Dre and Snoop Dogg, and held for the first time over two weekends (April 13-15, April 20-22) in Indio, Calif.

As reported yesterday, Iommi, 63, is working with his doctors to determine the best course of treatment. It is unknown if further live dates will be affected by his diagnosis, including a previously announced headlining slot at the Download Festival in England in early June.    

In November, the group -- Iommi, Ozzy Osbourne, Geezer Butler and Bill Ward -- announced album and tour plans. The album, Osbourne's first with the band since 1978, will be produced by Rick Rubin and is still on the schedule for a fall release through Vertigo/Universal.

Meanwhile, even without Black Sabbath, Coachella will still host several notable reunions, including influential hardcore bands Refused and At The Drive-In, as well as '90s alt-rockers Mazzy Star and Britpop icons Pulp, who got back together in 2011 but did not tour North America.