First the heartbreak, then a sliver of hope a matched bone-marrow donor will be found. Finally, the stark reality of so few prepared to donate in Australia.

But after her brother, Matt, died aged 39 almost three years ago, she's been left to wonder what would have happened if more Australians were registered to be blood stem cell donors.

Throughout an 18-month leukaemia battle, Matt struggled to find a blood stem cell donor.

Blood stem cell, or bone marrow, transplants are required for about 1000 people diagnosed with blood cancer in Australia each year.

But the country's donor list is short. Few Australians have volunteered to help.

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"There may have been a match for [Matt] in another state, in another suburb or even just down the street but matches can only be found when they are registered with the blood stem cell donor registry," Ms Bearham said.

While other countries have been able to establish long lists of donors through well-funded and effective cheek-swabbing programs, Australia has fallen well behind.

About $13 million has been promised to the Australian Bone Marrow Donor Registry to help the organisation promote the registry and encourage more donors. But the funding has been held up.

Australian Bone Marrow Donor Registry chief executive Lisa Smith said Australia had one of the smallest donor pools of comparable nations. A majority of donors to Australian patients come from overseas.

"The overwhelming majority of Australian patients cannot find a match within this country," she said.

This is despite it being incredibly easy to sign up as a donor. The registry accepts new people aged from 18 to 35. People can sign up online through Strength To Give, part of the registry, and they receive a cheek swab kit which they complete and send back.

But the lack of funding, combined with a lack of awareness, has made it harder to grow the registry.

"We've been calling on governments for several years now to increase investment into the recruitment of Australian donors onto the registry and to expand the opportunities for people to join so it isn't constrained by blood donation only because the rest of the world has abandoned that method in favour of cheek swabs you order online," Ms Smith said.

Ms Smith has warned the registry won't be able to keep sending out kits if they are not given funds.

"It is still operating off our own cash reserves ... it will be available for a few more months but certainly not for the whole year," she said.

"We are certainly encouraging people to sign up while we have our own funds and once those limited funds are exhausted we will continue to await state and Commonwealth governments decisions."

Federal Health Minister Mark Butler has previously acknowledged Australia was falling behind and has promised to work with state and territory counterparts to enable more funding.

"Australia has not moved fast enough to enable more effective matching of bone marrow donors with patients," he said last year.

"Part of the problem is that no single government - between the Commonwealth and the states and territories - has sole responsibility or sole authority to make sure Australia keeps pace with the rest of the world and makes advances in technology."

Ms Bearham has become a strong advocate for growing the registry since Matt's death.

"I wonder what would have happened, how Matt's story would have ended, had there been a blood stem cell donor match found for him in Australia," she said.

Matt found no matches in Australia but was matched with someone in Germany. However, the person had to pull out.

Ms Bearham was considered as a donor at one stage but she was only a 50 per cent match. When times grew desperate, doctors decided to turn to her.

"The doctors explained that in dire situations where no full donor match can be found, they can use a half-matched sibling. They explained that it wasn't ideal. But they said there may be no other choice," she said.

But results from blood tests prevented this.

"I apologised to him. I didn't know what else to do, what to say, all I was thinking was that my brother was probably going to die, because of me. Matt, as he often did, ended up consoling me: 'It's okay', he said in a calming voice. He told me it wasn't my fault and that I shouldn't blame myself," Ms Bearham said.

However, another donor was found for Matt, again from Germany. The stem cell arrived safely from Germany and the transplant happened.

"I will always be grateful to this person, even though I don't know who they are (strict confidentiality rules apply), they will always be a hero in my eyes," Ms Bearham said.

Matt ended up going into remission following the transplant but sadly, he became ill and had low immunity from his treatment. He died.

Importing donor cells is expensive and is fraught with risk. Ms Smith said this is why it was crucial to grow Australia's donor registry.

The registry accepts people aged 18 to 35 and has a target to have 150,000 Australians in this age range on the list. There are only about 60,000 in the age range at present.

Ms Smith said younger people were overwhelmingly chosen by clinicians and men were often chosen over women.

"There is a significant difference for young donors. A patient's long-term survival chances decrease by 3 per cent for every decade of a donor's age, so it really does matter," she said.

"If a clinician has a choice they will pick a young male donor and the reason for the gender is a little more complicated. It tends to be because male donors usually provide more cells, bigger donations. They are literally bigger-boned and the number of cells you can provide is another important factor, the more cells the better for the recipient."

Another factor which is important to the list is ethnicity and Ms Smith said the registry needed people from a broad range of backgrounds.

"You are much more likely to find somebody who matches with the same ancestry as the same part of the world with the same ethnicity," she said.

"For Aboriginal and Torres Strait Islander patients, of which I think there were about eight or so last year that proceeded to transplant, they really do need to have Australian-based donors. They're going to struggle to find donors overseas.

"It's not diversity for diversity's sake in this case; diversity is really a life or death matter for our patients."

A person will remain on the registry until they are 60. But Ms Smith said in order for it to be sustainable they needed about 25,000 new donors each year. At the moment, there were about 5000 new donors a year.

Most transplants are not very invasive and are similar to giving blood.

"The vast majority of donations are through giving yourself a short course of injections to stimulate your bone marrow. You spend half a day having your blood filtered like a dialysis process," Ms Smith said.

"Our donors report the injections, in particular, can bring on the sense you feel like you are getting the flu, you might get a bit of bone aches and quite often people after a donation will go home and sleep for a day but typically they're back on their feet in like a day or two."

There is only about a one in 1000 chance a person will ever be asked to donate. But that one in 1000 could make a huge difference to someone like Matt.

"You may never be called upon to donate. But for one person, you may be the only person in the world who can save their life, with a procedure that is very similar to donating blood," Ms Bearham said.

"You might be the only person who can step in for a sibling like me, who was desperate to save her brother, but couldn't. Please help to honour the memory of my brother by registering."