While promoting Jack's Mannequin in 2005, McMahon was diagnosed with a troubling case of laryngitis. But when it persisted, New York City doctors found on June 1, 2005, that he was suffering from acute lymphoblastic leukemia. His treatment included a bone marrow transplant from his sister Katie.

A year later, sitting backstage at KEDJ-FM's recent Edgefest in Tempe, AZ, the frail-looking-yet-healthy McMahon talked nonchalantly about the disease that hampered his ability to write songs and promote Jack's Mannequin's 2005 debut album "Everything in Transit." The set was released just two months after his diagnosis.

"'At the time that I got sick, my job was to get well not to write music," McMahon said. "I accepted that. There were times when it was hard. I would have loved to been in a place where physically and spiritually I was able to be writing instead of fighting cancer. But that wasn't the case, and I had to focus my attention on getting well."

Now that he is well--he was able to stop taking his medication this past July--McMahon is pushing Jack's Mannequin and "Everything in Transit," on which Tommy Lee appears on drums. Joined by Copeland, Daphne Loves Derby and The Hush Sound, Jack's Mannequin waged a 22-city "Tour for the Cure," which kicked off in September, Leukemia Awareness month. McMahon raised more than $125,000 to benefit The Dear Jack Foundation, a non-profit organization founded by McMahon to fund cancer research.

Now Jack's Mannequin is hitting arenas, opening for Panic! At the Disco through Dec. 9. The group begins a headlining tour with Head Automatica and The Audition Feb. 10 in Nebraska. Thirteen dates have been confirmed, and eight more will be announced in the coming weeks. Details are below.

"I've focused my attention on promoting this record," McMahon said. "I love it. I still love it. I still want as many people as humanly possible to hear it. I'm hanging on with every last fingernail until somebody tells me I can't sell another record. That's where I am with this album.

"We haven't really been in a position to promote a record as actively as we would have liked to in the early days. Now, to come out and do a big arena tour with the guys in Panic, we're definitely happy to be out here."

McMahon is also pleased that his record label, Maverick, was supportive during his illness, putting the Jack's Mannequin campaign on hold until he recovered.

"They've been fantastic," he said. "I feel really blessed to have encountered these people prior to such a serious time in my life. They are partners in my career that not only cared about selling records and making money, but actually cared about me. That's not something you find every day in the music industry. That's great."

When the promotion cycle for "Everything in Transit" comes to an end in March, McMahon will begin writing new material.

"Once I start actually get into the process of writing again, what I went through will manifest itself in my writing," McMahon said.

He said he is not sure if a Jack's Mannequin or Something Corporate album will arise next.

"I would imagine the next record I will do will be a Jack's Mannequin record. Not with the intention of being elusive--I can't say I even really know. I'll get home in March after touring this thing for about a year. I'll settle in and start writing songs again and see where the chips fall at this point."