The Bee Gees star was rushed to hospital last November for treatment, and was also treated by doctors for severe abdominal pains in April 2011.
The Mirror quotes a friend of Gibb as saying: "He's very strong-willed – if anyone can beat this, it's Robin."
The musician has also accepted a new role as patron of Hove MP Mike Weatherley's 'Rock The House' initiative, which champions both the UK live music industry and artists' intellectual property rights.
Gibb was unable to attend the launch on Wednesday (January 18) in person, but his long-term friend Mick Garbutt said at the event: "He would have absolutely loved to be here in person, but unfortunately that simply hasn't been possible with his health.
"It is true to say he is very unwell, but he's an incredible man and enjoys lots of support from his close circle of friends and family, and particularly from his wife Dwina."
Garbutt added: "He is receiving regular chemotherapy and fighting hard. He is also heading home to be with his family at every possible opportunity as that's where he feels comfortable, but the reality is that he is very unwell. He has set himself a goal to be at the gala performance of his first classical composition in April and everybody around him hopes that he will be there."
Gibb is currently working on the Titanic Requiem, which was commissioned to mark the centenary of the ship's sinking in April 1912.
> Bee Gees' Robin Gibb on liver cancer: 'I'm on the road to recovery'
Watch the video for 'How Deep Is Your Love' by the Bee Gees below: