Two and a half years ago, things couldn't have been better for Brian Daley. As hip-hop maestro DJ Swing, he had just triumphed over Fat Boy Slim to win a Mobo award for best DJ and was helping to run the R&B divisions of several major record labels.

Artists such as Bobby Brown, Mary J Blige and Jodeci were begging him to remix their tracks and every Saturday night he was top of the bill in the UK's best clubs. Things at home were good too, and he spent Sundays with his two children, Kasien and Sebastian, and their mother, his ex-partner, Juliet. Then, in January 2003, everything changed.

"One moment, I was rocking the decks and mixing," says Daley. "The next I was discussing the proteins in my urine and taking Thalidomide."

Daley had been diagnosed with a rare and complex blood cancer, multiple myeloma, which affects between 10,000 and 15,000 people in Britain. While not being acutely painful (hence its lack of early detection), the disease initially causes fatigue and aches, and leads to the body not being able to fight infection and the failure of the kidneys.

Today, according to the International Myeloma Foundation, the disease is one of the most rapidly increasing types of cancer in the western world. However, despite advances in treatment and increased levels of research, there is still no known cure. Survival rates vary from patient to patient. For Daley, a harsh regime of chemotherapy and fortnightly blood transfusions may be keeping the disease at bay temporarily, but what he really needs is a bone marrow transplant.

Though his condition is basically a death sentence, a transplant could improve Daley's quality of life and put his early funeral on hold. The trouble is, the odds are stacked against him finding a match because of the colour of his skin. As an African-Caribbean, with also Indian and German ancestry, at present he, and other mixed-raced patients, have only a one in 100,000 chance of finding a match, compared with one in five for Caucasians.

The main reason for this is the extreme diversity of tissue types among people with African ancestry, according to Orin Lewis and Beverly De-Gale, co-founders of the African-Caribbean Leukaemia Trust (ACLT).

"The problem is due to things like slavery, mixed marriages and mass immigration," says Lewis. "Racial diversity in the black community is massive, thus making the odds of finding a match tiny. Brian's background, like that of many others, is extremely complicated - African-Caribbean, Native American and German. Looking for a match is like joining the lottery of life."

In Britain, there are two registers that list more than 600,000 potential blood and bone marrow donors, both black and white: the Anthony Nolan Trust and the National Blood Service. Both are linked to other blood registers worldwide and have been established for more than 20 years. Of these 600,000, currently just 16,000 are from African-Caribbean donors.

He may be consigned to his sick bed most hours of most days, but Daley is determined that more black people should come forward and have their bone marrow tested. Although reluctant to be in the public eye again (he says his illness has made him very self-conscious of his body and the feeling it evokes in others), he's decided to raise awareness with the help of his clubland crew, the Boogie Bunch, and his family and friends. He also agreed to be followed by the film-maker Andrea Eisenhart, who has documented his and other people's searches for donors in a forthcoming Channel 4 programme, Saving DJ Swing.

The film follows Daley's fight with the disease, and the efforts of his friends to help by holding hip-hop club events which only allow entrance to those who have visited a blood registration clinic. It also trails Donna Benjamin, who is campaigning for people to register their bone marrow in churches where congregations have a high proportion of black and African-Caribbean worshipers.

After two years of therapy and his second stem-cell transplant (in which his own stem cells or bone marrow is extracted, cleaned and put back), doctors from the Catherine Lewis Centre at London's Hammersmith hospital are worried that Daley's condition is deteriorating. Tests seem to indicate that his cancer is creeping back after a few months of remission. The hospital has found him a nine-out-of-10 bone marrow match, which is not nearly as good as it sounds. The choice before Daley is harsh - choose a non-perfect match while his body is still well enough to tolerate the operation, or wait, on the chance a nearer match will turn up.

"Ten out of 10 would be much better because the doctors have told me the first 100 days are critical," says Daley, who is being treated by the specialist Dr Amin Rahemtulla. "The body naturally rejects implants during this time, and the mortality rate is higher if the match is not perfect."

The best chance for a perfect match would have been from a sibling, but his sister Beverly's bone marrow did not match. But Daley is optimistic that the existence of charities such as ACLT will continue to encourage more African-Caribbeans to register as potential donors.

ACLT was founded when Lewis and De-Gale's son, Daniel, was diagnosed with leukaemia in 1996. They were shocked to discover that only 600 black matches were on any national registry. In a bid to help their son, and others like him, they decided to have mass registration drives and road shows. Sometimes, they literally went out into the streets and started talking to people.

Today, because of their efforts, more than 15,400 black people have registered. More amazingly, six years ago, against the odds, their son found an exact-match donor - a girl in Detroit, Michigan.

"Waiting for a match is very difficult," says Lewis. "But you must never give up hope because the next person who registers could be the one who helps you. Daniel is now a strapping 18-year-old. Miracles do happen. My son is proof of this"

While DJ Swing has yet to find his miracle, and the search for a perfect match is becoming increasingly urgent, he says he is at ease with the prospect he might not find one. "It's not my decision. It's the disease's decision. I am just grateful for being around right now."

Essentially, he says, knowing you have limited time means you have time to prepare. "In some ways this comforts me. The hard thing about being this close to death is that people either pity you or don't know what to say. It makes me sad that I evoke this feeling in others. I just hope the film makes people more aware, and that we can get more people on the register. At least that is something positive to focus on."

· To register your bone marrow type, call either the ACLT on 020-8667 1122 or the National Blood Service 0845 771 1711. For information on myeloma go to Myeloma.org.uk
Saving DJ Swing is on Channel 4 tonight at 11pm