Doctors for the 54-year-old former Buffalo Bills star are leaning toward surgery Thursday or perhaps April 1 at a New York City hospital, brother Dan Kelly told The Associated Press on Tuesday.
Kelly's doctors in Buffalo said March 14 the cancer was found to have returned when Kelly had follow-up tests after surgery last June to remove cancerous cells from his upper jaw.
Since then, wife Jill Kelly has been providing updates on social media. In a March 21 blog post she described the hospital rooms "where we 'huddle-up' as a family to call the next play and plan the next move now that the cancer's back, aggressive, and starting to spread."
The couple's daughter, Erin, a college student, on Saturday posted a photo showing her lying next to her father in a hospital bed, her head resting on his right shoulder as they watched college basketball.
"Watching the Syracuse game with daddy ... he's my buddy! Love him so much!!" read the post.
Two March 21 photos she posted show former teammates Andre Reed, Bruce Smith and Thurman Thomas smiling with Kelly during a visit at his home.
News of Kelly's cancer has brought an outpouring of well wishes from the community and beyond for the family, which has remained in Buffalo since Kelly's retirement from football following the 1996 season.
Kelly spent 11 seasons with the Bills and was the face of Bills teams that made four consecutive Super Bowl appearances in the early 1990s, only to lose them all. He was inducted into the Pro Football Hall of Fame in 2002.
Jim and Jill Kelly established the Hunter's Hope Foundation here in 1997 after their son, Hunter, was born with Krabbe disease, an inherited degenerative disorder of the central and peripheral nervous systems. Given little more than three years to live, Hunter died at age 8 in 2005.
"So incredibly overwhelmed and thankful" for "the multitudes who are praying for Jim," Jill Kelly wrote on Twitter on Sunday after the congregation at the Chapel at CrossPoint in the suburb of Getzville prayed for Kelly in a service streamed online.
"He's strong," Dan Kelly said. "Jim is humbled by all the prayers coming in."
AP Sports Writer John Wawrow contributed to this report.