I'm very sad to hear this news, and send out healing thoughts to John McVie.
There aren't many details available at this time. The remainder of the world tour was cancelled and the band was forthcoming as to the importance of the reason:
(Reuters) - Fleetwood Mac bass guitarist John McVie has been diagnosed with cancer and the rock group has canceled the Australian and New Zealand leg of its world tour so that he can undergo treatment, the band said on Sunday.
The band, known for such 1970s hits as "Don't Stop" and "Dreams," had just completed the European segment of the tour. It was to make 14 stops in Australia and New Zealand, the group said in a statement on its website.
McVie, 67, "is now scheduled to be in treatment for cancer during that period of time," according to the statement.
"We hope our Australian and New Zealand fans as well as Fleetwood Mac fans everywhere will join us in wishing John and his family all the best," band members Mick Fleetwood, Stevie Nicks and Lindsey Buckingham said in the statement.
McVie joined Fleetwood Mac shortly after its formation in London in 1967. He was inducted into the Rock and Roll Hall of Fame in 1998.