On March 9, John Mayer announced that he is being forced to cancel his upcoming 2012 Spring Tour in order to receive treatment for a returning granuloma, which is a growth that occurs in the throat and is exacerbated by the vocal cords making repeated contact.

Mayer was initially diagnosed with the condition last fall, with doctors placing him on extensive vocal rest at the time. This led to a nixed appearance at September 2011’s iHeartRadio Music Festival in Las Vegas and another with Tony Bennett in Los Angeles.

The cancellation has also forced a delay in the release of Mayer’s fifth studio album, “Born and Raised”, which is now scheduled to launch in May 2012.

In a letter to fans on johnmayer.com, the musician discussed his decision.

“During rehearsal on Tuesday, it came to mind that I should see my throat doctor because something didn’t feel/sound right. I went in for a visit on Wednesday and a scope of my vocal cords revealed that the granuloma has grown back where it had mostly healed,” Mayer wrote.

Mayer continued, “Because of this, I have no choice but to take an indefinite break from live performing. Though there will be a day when all of this will be behind me, it will sideline me for a longer period of time than I care to have you count down.”

Mayer is not rescheduling any concerts at this point, but will proceed with the May 2012 release of “Born and Raised” as planned. The singer promised fans that he would use his down-time to start writing his next album, adding, “I feel really vibrant as a writer at the moment and there’s no reason not to begin the next album project in the time I would have been touring.”

Mayer had been scheduled to play in 21 cities this spring, including this weekend’s SXSW conference in Austin, TX.

The musician made his announcement just months after hit pop artist Adele had to cancel her tour due to throat problems. In October 2011, Adele announced the cancellation of a 10-city U.S. tour due to the return of a throat hemorrhage she had first experienced in April 2011. The April hemorrhage had forced the postponement, then cancellation, of several dates at the end of her North American tour.

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Ultimately Adele’s doctor identified a polyp on a vocal cord, and she underwent surgery in November 2011.

The pop star made her triumphant return to the stage at this February’s Grammy Awards, where she also collected six awards for songs in her 2011 album, “21”. Her current plans are to return to the studio, contradicting a December statement in Vogue in which she talked about taking a few years off to write her next album.

Other musicians facing injury in recent years include rocker Lenny Kravitz, whose throat issues in 2008 forced him to cancel shows in British Columbia and New York, and, of course, Bono, whose 2010 back injury and subsequent surgery forced U2 to postpone the North American leg of their 360° tour for one year.

But what about the impact of these physical ailments on performers’ ticket sales? Mike Janes, general manager of Event Ticketing at ticket search engine Fansnap.com, sees no ill effects, at least on major stars on the music scene.

“While a tour cancellation is particularly disappointing to the artist’s hard core fans,” Janes said in a recent conversation with TicketNews, “we find they are highly likely to buy tickets whenever the tour returns.

In fact, it may leave fans more motivated to see the elusive star.

“Adele is a great example of where, if anything, her tour delay has created even more demand given her Grammy success.”

There is one type of fan, however, that Janes sees these kinds of disruptions affecting.

“I think the risk these days is the more casual fan, who doesn’t lack for entertainment options with so many tours on the road. After a tour cancellation, there is no guarantee at all these fans will buy tickets a second time.”

So, with hard-core fans filling the ranks of John Mayer’s and Adele’s bases, they probably have little to worry about in terms of future ticket sales.