‘Keep roaring’: Katy Perry sends video message to Toronto teen battling brain cancer

Olivia Wise is battling brain cancer.

Two weeks ago, we shared the Toronto teen's inspiring cover of Katy Perry's 'Roar.'

According to the video's description, "She couldn't walk or stand, she didn't have her full breath or the energy she used to, and she was managing her new pains and new limitations. While her physical condition was rapidly fading, her spirit remained untouched."

It didn't take long for Olivia's version of the song to go viral. As Olivia had hoped, it even reached Katy Perry, who recorded a video message to the brave teen earlier this week.

"I just wanted to reach back out to you and tell you that I saw your video and I was very moved and you sounded great. For being in the studio and making your wish to record that song, I thought that was really cool," the pop star says.

"I love you and a lot of people love you and that's why your video got to me and everybody that saw it. So I just wanted to send you some love and some light and tell you that I'm thinking about you. Thank you so much. Keep roaring."

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Olivia's family has set up a fund through Sick Kids Hospital in support of brain tumour research.

The success of Olivia's 'Roar' cover has helped them raise more than $25,000 of their $50,000 goal so far.

Olivia's video is inspiring her peers at Sick Kids, too.

"Hey, I am also a sick kids [sic] patient. I just wanted to let you know that this video inspired me. Even though my kidney disease is not as bad, I wanted to let others know about what sick kids [sic] does. So when my teacher put on this video I thought if she can do something I can to [sic]! I might not make a big difference but that's ok. I just want to thank you for being you and I want you to know your [sic] amazing :)" wrote Robin Fryer.