Their work with the likes of Amnesty International, Live 8, and Make Poverty History is well-documented. 

But it seems that the boys from U2 are also willing to go above and beyond for less high-profile worthy causes – namely a teenager with cancer who's had to endure multiple rounds of chemotherapy.

Colorado-native Lizzy Lawton is still just 14. But she's been battling a rare, aggressive form of bone cancer since 2010. Back then, following the discovery of tumour on her hip, she was given a just a seven percent chance of living beyond a few months.

Then another tumour was found on her shoulder.  

Ten rounds of chemotherapy followed, and Lizzy was even cancer-free for a year – until a scan revealed a third tumour in her skull.

"Her head had been hurting her for a while, but she didn’t want to tell us because she didn’t want to hurt anybody," Lizzy's mother Meredith told PEOPLE.

Now, after five years of living with the disease, she is about to face into another 12 bouts of chemo.

However, when the Lawton family saw that U2 was playing nearby Denver as part of their Innocence + Experience tour last Sunday, they reckoned it would be the perfect outing. The only issue? Tickets were €265 a pop.

Luckily a friend stepped in, raising €4,200 via a CrowdRise fundraiser: the tally was enough for the tickets, as well as a limo ride to Denver from their home. Lizzy and her two sisters were also given makeovers. 

Then CrowdRise co-founder and actor Edward Norton heard of the Lizzy's story. He called Bono – and got the family's seats upgraded, along with backstage passes and an introduction to the band themselves.

"When we got into the limo, there were gift bags, and one of them had an iPod in it for Lizzy," Meredith explained. "She was over the moon about the iPod – then we found out we got to go backstage!" 

There, Meredith reported: "Bono kneeled down and kissed Lizzy's hand. 

"I don’t really know if you can call a rock star a sweetie pie, but that's what he was." 

The Edge was the next member of U2 to swing by, sharing his own family's experiences with cancer – his daughter, Sian, had leukaemia as a child.

"A lot of people just walk by because they don’t know what to say and they're uncomfortable with dealing," Lizzy's mother also said.

"These guys weren’t uncomfortable.

"In the back room, they weren’t even celebrities, they were just sweet, kind human beings being sweet and kind to other human beings." 

Understandably, Meredith describes the experience as "the best night ever".