Answer by taking a quote from the following article:

Cancer Bats are a Canadian hardcore punk band from Toronto, Ontario. They have released five studio albums and six extended plays. The band is composed of vocalist Liam Cormier, guitarist Scott Middleton, drummer Mike Peters and bassist Jaye R. Schwarzer. Cancer Bats take a wide variety of influences from heavy metal subgenres and fuse them into hardcore and punk rock, and also include elements of Southern rock.

Cancer Bats was founded in May 2004 by singer Liam Cormier and guitarist Scott Middleton, a former member of Toronto heavy metal band At the Mercy of Inspiration. The two wanted to form a project that combined their favorite parts of bands like Entombed, Refused, Black Flag, Led Zeppelin and Down, among others. The lineup was completed with the addition of Andrew McCracken on bass and Joel Bath on drums, with Cormier moving to vocals. The four-piece wrote and recorded songs for a self-released demo that saw light in January 2005, and led to Canadian independent record label Distort Entertainment signing the band.  The story is that the band considered the names Cancer Bats and Pneumonia Hawk after deciding that a combination of illness and animal name would give the best band name. Soon after, Mike Peters replaced Bath on the drums and the band began playing throughout Southern Ontario, playing live shows with bands like Billy Talent, Every Time I Die, Nora, Alexisonfire, Haste the Day, It Dies Today, Bane, Comeback Kid, Buried Inside, Attack in Black, Misery Signals, This Is Hell, Rise Against, The Bronx and Gallows.  On June 2, 2006, the band took part in a short interview and then played a free CD release show at The Edge 102.1 (CFNY-FM) and then on June 6 Birthing the Giant was released into major record stores. The album includes guest vocals by George Pettit of Alexisonfire. On June 7, 2006 they hosted All Things Rock, a show on MTV Canada, and had their own video played at the end of the show.

How did the demo do?
led to Canadian independent record label Distort Entertainment signing the band.