You’ll meet them at health fairs, schools and churches: volunteers who ask for a cotton swab of DNA and your consent to join the national bone marrow registry.
The registry is a massive database of potential donors for people with blood cancers, sickle cell anemia and other life-threatening conditions. Donors and recipients are “matched” by comparing their HLA markers, small proteins that are inherited from their parents and found on most cells in their body. Not every patient is able to find a full donor match, and match rates are significantly lower for minorities. Despite recruitment efforts, African-Americans have just a two in three chance of finding an unrelated donor in the registry, according to BeTheMatch.org.
But what if a donor didn’t have to be a full match? What if a "similar" match could work, too?
Recent successes in stem cell transplants from so-called "half matched" donors have led some cancer centers to start considering the procedure for patients who have no other options. Washington University in St. Louis has completed 80 of these half-match transplants since 2011; 56 of them in the past year alone.
One of them was Samantha Carter.
By her 30th birthday, Carter had already survived years of chemotherapy, different types of treatments and two relapses of Hodgkin’s Lymphoma, a cancer that attacks the immune system.
In July of 2014, the specialty drug she had been taking stopped working.
”That’s when they said you have to get a transplant, and you have to get a donor,” Carter said.
Carter’s transplant would be through apheresis—a process that involves drawing blood from a healthy patient, separating out stem cells and injecting the fluid into the sick patient.
But, finding a donor posed a challenge. Carter, who is African-American, has no full siblings, only half-brothers and sisters. A search for an unrelated donor in the bone marrow registry also came up negative. So Carter’s doctors at the Siteman Cancer Center decided to move forward with a half-match transplant from her 20-year-old sister, Anna.
Only recently have doctors had success with bone marrow transplants in patients whose donors share only half of their HLA markers. When it was first attempted in the 1980’s, it was a disaster, according to Dr. Rizwan Romee of Washington University in St. Louis. Patients’ immune systems would reject the donation, and some died from septic shock.
Washington University is one of just a few cancer centers nationally that began using a technique for half-match transplants in 2011. Although it was first developed by researchers at Johns Hopkins University, Romee said his team modified the regimen slightly, using stem cells taken from peripheral blood instead of bone marrow tissue.
“It looks like our one-year survival rate using the modified Hopkins regimen is about the same as one-year survival rate using fully-matched donor transplants,” which is about 60 percent. “That’s huge,” Romee said.
Carter received her transplant in September of 2014, after a round of chemotherapy. She spent 22 days unable to leave the hospital floor where her room was located, as she waited for her half-sister’s stem cells to take over her immune system. Knowing that exercise would help her recover more quickly, Carter relieved her frustration by walking each day.
“I knew from the last year that eleven laps around the floor is a mile,” Carter said. “I’m a fighter, and I didn’t want to be there.”
Of the 80 half-match transplants done at Washington University, almost a quarter went to African-American patients. By comparison, 0.04 percent of Washington University’s 424 full-match transplants from unrelated donors during that same time period were for African-Americans.
The implications are striking. Lower donor registration rates among minorities have long contributed to disparities in the likelihood of finding a match for bone marrow or stem cell transplants. Having mixed ancestry, or ancestors who migrated from widespread geographic areas, can give a person a unique combination of HLA markers. But if a half-match donation is possible, patients are much more likely to have family members who are potential donor matches.
Romee said that means patients may also be able to get a transplant more quickly. The process of finding an unrelated donor can take two to three months; a precious amount of time for people battling blood-related cancers.
On January 9th, Carter’s latest CAT scan showed no traces of the cancer. It was her first "clean scan" in more than a year. She’s back to working full time in an outpatient clinic at Barnes Jewish Hospital, where she coaches cancer patients through their treatments. She and her fiancé are making plans to marry in September. She smiles when she touches her closely cropped hair—it’s growing back.
“I went back to the gym last week,” Carter said. “I’m back to my normal self.”
