The bassist learned he was ill in October (13), and he is currently balancing treatment with gigs.
Nicks insists her bandmate is doing well ahead of surgery next week (beg13Jan14).
She tells Us Weekly magazine, "He's got his treatment, and now he did a show on the 30th and 31st (December), another tomorrow night, then he has surgery next week... I'm not the least bit worried about John. He's very, very strong and a man of very few words. He's not a person to mess with.
"If I ever had any psychic knowledge about me in this body, I am telling you that John MCVie is gonna be just fine... He's gonna have a little operation. He'll probably take a couple weeks to recover, and then sky's the limit!"
Fleetwood Mac cancelled 14 tour dates to allow MCVie to undergo cancer treatment, but the bassist was back onstage for the band's New Year's shows in Las Vegas.