The 61 year old was rushed to the hospital last Tuesday after a 911 call from his mansion home in Oxfordshire, central England, but allowed home after a few hours, the Sunday Mirror reported.
A previous emergency admission on Oct. 13 with intense stomach pain was blamed officially on "inflammation of the colon." But the newspaper, citing an unnamed close family friend, suggested Gibb was diagnosed with the potentially-fatal disease several months ago.
The singer had emergency gastro-intestinal surgery in August 2010, and in April of this year chronic pain forced him to postpone a solo tour planned for South America after his medical team advised him not to travel.
He recently pulled out of several public appearances and was photographed last week looking emaciated and in pain.
Fans had feared originally that the "Stayin' Alive" singer was suffering from the same condition that contributed to the unexpected death of his twin brother and former bandmate, Maurice. Maurice Gibb died from a heart attack in 2003, aged 53, during surgery for a twisted intestine.
Robin Gibb discussed his struggle to come to terms with his brother's death in a program due to be televised Sunday by UK satellite channel Sky Arts.
"[It's] something I haven't accepted," he told the "Living The Life" show. "I just imagine he is out there somewhere and I will bump into him one day."
The Bee Gees temporarily retired after 45 years of entertaining following the death. But in 2009, the group's remaining members, Robin and his brother Barry, 65, announced they would begin performing again.
Barry and the brothers' elderly mom, Barbara, flew from the U.S. to be close to Robin last week. Robin Gibb wrote on his official blog that, "We all had a great time but most of all it was the best tonic ever to be with Barry again and making plans!"
The Gibb family has yet to make any official statement on Sunday's report.