'Four Percenters'

The Challenges of Finding a Mixed Race Bone Marrow Match
Krissy Kobata knows what it is like to wait.

For more than 10 years she waited for a bone marrow donor, while inside her body simmered a blood disease called myelodysplastic syndrome.

As Kobata grappled with her condition, she saw friends and acquaintances in similar situations — people whose mixed heritage was a barrier to transplant — do the same. Sometimes in vain.

“Emotionally, I am a ticking time bomb,” said Kobata, whose father is Japanese and mother is Caucasian, in an interview with Glamour in 2012. “Without a transplant, this disease will eventually kill me.”

Finally, Kobata’s care team at City of Hope, which had been monitoring her condition, said she could not wait any longer. She needed a match right away.

“I was getting sicker and sicker,” said Kobata, 35. “And by that time I was really scared.”

For minorities and mixed race patients diagnosed with life-threatening blood cancers, bone marrow transplants (BMT) offer a second chance, and may be their best hope for a cure. But these patients face an added layer of difficulty when seeking bone marrow matches either within their extended family or from an unrelated donor on the Be The Match registry.

Only 4 percent of donors on the registry are of mixed-race background.
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Kobata's mixed heritage made bone marrow donation a challenge

“Bone marrow matches get more complicated the more racially mixed we are, and makes things much more difficult for patients,” said Jill Kendall-Erb, program director for the Be the Match program at City of Hope. “It’s a very big deal because it means you have a donor base that is huge and vast and wide for Caucasian patients, but not for minority patients.”

The best matches tend to come from immediate family members. A patient has about a 25 percent chance of matching a sibling. But even in large families, there is no guarantee.

Kobata thought her older brother, Randy, might be a potential donor. But he was deemed too risky because he had had a medical issue that could compromise the procedure.

“He was devastated,” said Kobata. “He cried on the way home. He’s my big brother. He’s always taken care of me. He wanted to be the one to save my life.”
 
When a new patient needs a transplant, if you don’t find a perfectly matched sibling, or someone from the family, scientists eventually go to the registry for an unrelated match.
 
“When we are looking for matches, we are looking for people who have the same markers on their white blood cells,” said Kendall-Erb. “And what we know now is the certain sequences, or types on those white cells, are more common in certain ethnic groups.”

What scientists are looking to match are components of bone marrow called human leukocyte antigen (HLA) type. HLAs are protein markers on cell surfaces whose normal job is to allow the immune system to distinguish between normal and abnormal cells.

When it comes to blood or bone marrow transplantation, those same HLA markers are used to determine whether a person in need of a transplant has a donor who matches. And people of similar ethnic backgrounds are the most likely to have them match.

REGISTRY OVERWHELMINGLY CAUCASIAN

For minorities and mixed-race patients seeking a match on the registry, finding donors from a similar ethnic background can be challenging.

Of the nearly 15 million Americans registered, only a small fraction are African-American, Latino, Asian or of mixed race. About 9 percent are Latino, 6 percent are African-American and Asian and only 1 percent are American Indian or Alaska Native.

About 85 percent of donors are Caucasian.
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Deputy Chavez in hospital

"The numbers are quite staggering,” said Athena Mari Asklipiadis, founder of Mixed Marrow, an outreach group that finds mixed race donors. “People compare it to winning the lottery.”

And Caucasians are not always spared when it comes to the difficulty of finding matches.

“Even ‘Caucasian' is not really a single group genetically,” said David Senitzer, Ph.D., former director of City of Hope’s HLA laboratory, which finds patients the best-matched donor. “There are many different groups and there are a lot of shared antigens among those groups. It’s the same for African-Americans, just not quite as frequent.”

Because Be the Match, operated by the National Marrow Donor Program, or NMDP, is volunteer-based, the registry is only composed of those minorities and mixed-race donors who have signed up.

It is more complicated to find a match for a patient of mixed heritage because they have “more sequenced changes” in their HLA, said Kendall-Erb.

“You might have a husband who is Filipino and a wife who is Hispanic, and they have a child, and we are looking at HLA that could have been inherited from either side,” she explained. “So it gets more complicated the more racially mixed we are. And it makes matching that much more difficult.”

For minorities of Mexican descent, like Los Angeles County Sheriff’s Deputy Jorge Chavez, 43, the search may be uncomfortably long. The father of four, who has acute myeloid leukemia (AML), was unable to find a match for many months, even among 600 family members and friends.

Doctors analyzed Chavez’s HLA tissue type and attempted to match it with a donor whose HLA proteins (or markers) were closest to his. The better the match, the more likely the transplant will succeed.

In the end, while Chavez was not able to find a “perfect” match — one that met 10 out of the 10 markers — he was able to find a donor that was a close enough match for a transplant.  

Finally finding a match, “Put my spirits on full throttle,” said Chavez.

'Great, I'm a White Guy'

After being diagnosed with AML, Gary Stromberg was in the same situation as Kobata and Chavez: He needed a DNA match and a bone marrow transplant.

“I said, ‘Great, I’m a white guy. I’m in a big group,’” said Stromberg, to laughter at the 42nd Annual Bone Marrow Transplant Reunion (BMT Reunion), held recently at City of Hope.

“They said, ‘Not so fast white boy. You’re an Ashkenazi Jew and that’s a separate and smaller category.’ If a donor is to be found it will likely be from that group.”

“We see our Jewish patients really struggle,” said Kendall-Erb.

That is because an estimated 6 million Ashkenazi Jews were killed in the Holocaust, the aftermath of which limited the number of available donations.

Stromberg eventually was matched to a donor from Israel, Alex Kikis, but he knows he is lucky.
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Stromberg and Kikis
 
“When I look Alex in the eye I want him to see the man whose life he saved, and I hope he appreciates the gift that he gave me,” said Stromberg. “All the recipients like me are alive today are because of somebody doing what Alex did for me.”

Because the registry is anonymous and volunteer based, most patients never get this once-in-a-lifetime chance to say ‘Thank you.’”

“It’s overwhelming,” said Kendall-Erb, of the reunion. “It invigorates my staff, it’s what keeps us going — when you see our work ends up here.”

WIDER POOL OF DONORS 

Although most donors still come from the United States, the U.K. and Germany — countries with predominantly Caucasian populations — the number of minorities and mixed-race donors in the global registry is slowly growing.  
 
“Now because of the internet, NMDP, the American registry, is hooked up to registries in Japan, Australia, France and all over the world,” said Senitzer.

This widens the pool of potential donors for patients like Kobata who are looking for donors to match their own ethnic background.
 
“Thousands of patients each year who would benefit from a transplant still do not have a match,” said Kendall-Erb. “It’s important to increase the number of people on the bone marrow registry and add diversity. There’s an increased need for people of mixed ethnic background and minorities to join.”
 
Potential donors can sign up by filling out a medical questionnaire to see if they meet the health requirements. Next, volunteers swab the inside of their cheek, and mail the sample back for testing. Those identified as a potential donor are contacted for additional testing.   

Kobata said her next wait — to hopefully one day meet her donor — will be worth it.

“It’ll be a long conversation that I’ll be looking forward to having,” she said. “Hopefully imparting to her what an incredible gift she gave me.”
 

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