Lou Koller, the longtime frontman and co-founder of New York hardcore band Sick of It All, has died after a two-year battle with esophageal cancer. He was 59.

The band announced Koller’s death Friday in a statement shared on Instagram.

“It’s with unbelievable sadness that we announce to our worldwide hardcore family the passing of our brother Lou Koller,” the group wrote. “The level of loss that we feel at this time is overwhelming.”

“We have lost a beloved friend and an iconic frontman. Lou had the power to raise everyone’s spirits at our shows with a smile and a sarcastic comment, and he won people over wherever we played, from every culture and every corner of the world.”

The statement continued, “This year would have marked Sick of It All’s 40th anniversary as a band, and Lou’s camaraderie, commitment and enthusiasm were always steadfast throughout the years.”

Koller first revealed in June 2024 that doctors discovered a cancerous tumor in his esophagus that spread into his stomach, forcing the band to cancel its European tour while he underwent treatment.

After months of chemotherapy, the rocker shared in May 2025 that he was cancer-free. However, just a few months later, he revealed the cancer had returned.

“So bad news is the cancer has returned,” Koller said in a video message at the time. “I’ll try to keep you updated as much as possible. Thank you for your love and support.”

Fans and fellow musicians rallied around the singer throughout his illness, helping raise money for his medical expenses through benefit concerts and fundraisers.

In the band’s tribute, Sick of It All thanked supporters for standing by Koller during his final years.

“You all helped Lou feel very special and very loved as he battled away these last two years,” the band wrote. “His battle is over now and he can finally rest. Hopefully he can somehow still see and feel the beautiful, positive mark he left on the world.”

Tributes quickly poured in on Instagram, including from WWE star CM Punk, who wrote, “Love you Lou and SOIA. Thank you for the soundtrack for my life. Sending hugs.”

Singer-songwriter Chuck Ragan also wrote, “Lou was indeed a pillar in our world of music to me and will never be forgotten,” while Pennywise guitarist Fletcher Dragge added, “No words, a true gentleman and a pioneer, when I think of Hardcore, Lou is the first name that pops into my mind, thank god we had the privilege to enjoy the stage with him and the boys many time over the years, he was always a unforgettable presence on the stage, and one of the best hangs off the stage as well.”

Meanwhile, Pennywise’s lead singer Jim Lindberg wrote, “The best to do it, and a real good human. Devastated for your loss, for the family, for all of us. I can remember playing shows with you guys and hearing the strength in his voice and thinking, ‘How am I supposed to follow that?!!” Many Bro Hymns will go out to Lou now. Rest easy brother and love to all.”

Born and raised in Queens, New York, Koller co-founded Sick of It All in 1986 alongside his brother Pete Koller and drummer Armand Majidi. Over the next four decades, the band became one of the defining acts of the New York hardcore scene, releasing 12 studio albums and earning a devoted international following.