Cronin, who was diagnosed with the disease five years ago, died Wednesday at Brigham and Women's Hospital in Boston, said Melissa Holland, his business partner.
"Summer Girls," the boy band's most popular song, after touring Europe with LFO and performing pop songs that he said he didn't really believe in.
Depressed and "ready to call it quits," he later said, he penned the pop culture mash-up that showcased a penchant for offbeat wordplay. He referenced Larry Bird's jersey one moment and sonnets by "Billy Shakespeare" the next.
"I just thought back to when I was young, happy, no worries," Cronin told the Boston Globe in 2005 and said he filled the song with "inside jokes."
"I never thought that anyone besides my close friends would ever hear it," he said.
Leaked to a radio station, the hip-hop pop tune peaked as a Top 5 single in summer 1999, thanks in part to what Billboard magazine called an "ultra-hooky" chorus:
New Kids on the Block had a bunch of hits
Chinese food makes me sick
And I think it's fly when girls stop by for the summer, for the summer
I like girls that wear Abercrombie & Fitch....
In 1996, Cronin formed LFO — an acronym for Lyte Funky Ones — with Brad Fischetti. They traveled to Orlando, Fla., "on a whim" and knocked on the door of producer Lou Pearlman, Cronin told the Boston Herald in 2000.
"He had just signed the Backstreet Boys and 'N Sync," Cronin said in the Herald interview, "and then he signed us. It was cool because we were all … trying to make it."
Once vocalist Devin Lima joined the lineup, LFO toured with the Backstreet Boys and 'N Sync before releasing a self-titled debut album in 1999. In addition to "Summer Girls," the album produced another hit single, "Girl on TV," which Cronin also wrote.
Record producer Clive Davis told Billboard in 1999: "Backstreet Boys may be the target and the model, but what's very unique here is that Rich is writing these songs. These guys are raising the standard" for boy bands.
LFO toured for another two years with Britney Spears and others, and recorded the 2001 album, "Life Is Good," but the group faded away along with the boy-band craze. They broke up in 2002 but reunited briefly last year for a tour.
He recorded a solo album and in 2007 starred in the VH1 reality series, "Mission: Man Band," which made a new group from old pop acts, an experience he likened to a "train wreck."
Born Aug. 30, 1974, in Roxbury, Mass., Cronin grew up in nearby Kingston, Mass., and studied advertising at what is now Bridgewater State University in Massachusetts.
After he developed leukemia, he founded the Rich Cronin Hope Foundation in 2005 to raise awareness about the disease and help build the national bone-marrow registry.
Cronin is survived by his parents, Richard and Doris; a brother, Michael; and a sister, Cassandra.