15 Nov 2024

Research blog: the power of cord blood for leukaemia treatment

When treating blood cancers like leukaemia, a stem cell transplant can be a crucial option, especially after a relapse. Finding the right donor is key, and stem cells for transplants typically come from either bone marrow or umbilical cord blood (UCB). While cord blood transplants offer unique advantages, they are not as widely used in the UK as you might expect. In this article we explore the different types of stem cell transplant with Professor Alejandro Madrigal, a Leukaemia UK Trustee and leading expert in the field to get his take on stem cell transplants and the future of this treatment option.

Research shows that cord blood transplants can be as effective as those from unrelated donors or partially matched relatives. This is particularly true in cases when finding a match can be challenging, for example for ethnically diverse individuals. This makes UCB a viable alternative for many patients. According to Professor Alejandro Madrigal, “practically every patient in need of haematopoietic transplantation can find an acceptable and appropriate donor” due to improved results in recent years, largely thanks to rigorous clinical trials and the expansion of donor registries. However, the critical factor remains “the degree of matching between the donor cells (either from a mismatch related, haploidentical [meaning a person shares half of their genetic markers with another], unrelated, or cord blood) and the patient.”

Through the advancements in technology and the expansion of donor registries worldwide, we’ve succeeded in making the world feel smaller and more connected. Through facilitating the global exchange of information between donors and patients, we’ve greatly improved the chances of finding a match. In Chris’s case, this not only led to a match but also to the discovery of a lifelong friend.

Chris was diagnosed with acute myeloid leukaemia (AML) in the autumn of 2011 after becoming exhausted and struggling to walk. The police officer from Oxford underwent six months of chemotherapy. The treatment was a success, and Chris was then told his best chance of remaining free of leukaemia was a bone marrow transplant. A donor was found in Germany. Chris made an excellent recovery from the transplant. But he was curious about the donor who’d given him a new life. The hospital said if he wrote a letter to him, they would pass it on. To Chris’s delight, his donor, Thomas, wrote back.

Friends-for-life: Chris’ AML story – Leukaemia UK

Why Cord Blood Transplants Matter

A study highlighted that, among 54 countries (i), South Korea had the highest rate of cord blood donations at 6.8%, while the UK lagged behind at just 0.03%. This is significantly lower than most of the EU, where donation rates average around 0.7%. The UK also has only 7 hospitals equipped to collect and store cord blood, and private collection can be very expensive.(ii)

In May, we discussed traditional bone marrow stem cell transplants, which are crucial in treatment. One of the main challenges is finding a suitable donor, particularly for those from diverse backgrounds. However, cord blood presents a promising alternative. In 2021, there were 624,828  babies born in the UK.(iii) If we had collected cord blood from all these births, we would have a vast and valuable database for treatment opportunities.

Cord blood transplants offer several advantages over bone marrow stem cell transplants:

• Less severe Graft-versus-Host Disease (GvHD): umbilical cord blood transplant (UCBT) generally results in less severe GvHD, a serious complication where the donor’s cells attack the patient’s body.
• Quick and easy availability: collected at birth and stored until needed, cord blood is readily available, reducing the waiting time compared to finding a bone marrow donor.
• Flexibility with matching: Cord blood can be used even when a perfect match isn’t available, expanding the pool of potential donors.

Prof. Madrigal also highlights that another important factor in successful transplants is “the age of donor cells.” He notes, “Transplants using cells from young donors have better chances of success than from older donors, and this concept may extend to the use of cord blood.”

For adults, using two units of cord blood can make UCBT more feasible by providing enough cells. However, in children, using two units hasn’t shown clear benefits and may even increase the risk of GvHD, indicating that bone marrow stem cell donation is still the most viable option for children. Despite this, cord blood might still be the best option for patients with a high risk of leukaemia recurrence.

Challenges and reasons for the reduced use of UCBT:

Despite its benefits, cord blood transplants have seen a decline in use. Key reasons include:

• Delayed recovery: UCBT often results in slower recovery times compared to bone marrow or blood stem cell transplants, prolonging the healing process.
• Higher risk of treatment-related death: the slower recovery can increase the risk of life-threatening complications, such as infections.
• Infrastructure: obtaining parental consent, collecting and storing samples requires trained personnel and financial resources for storage.
• Emerging alternatives: newer methods, like HLA-haploidentical transplants, which use cells from a half-matched donor, are proving to be effective alternatives with better matching and fewer complications.(iv)

Researchers are exploring ways to enhance the effectiveness of cord blood transplants, including improved matching techniques and innovative preparations to reduce complications. There are also promising developments in using cord blood for advanced immune cell therapies to fight leukaemia more effectively.

However, as Prof. Madrigal points out, “published outcomes comparing donor sources are somewhat comparable, and the best choice is still debated.” He emphasises that “no single method of transplantation is superior to others. Rather, the selection of the best graft may be mediated by donor and patient factors such as age of donor and patient, disease and disease status (relapse, first remission, etc.), possible gender of the donor and the recipient, and other variables.”

For example, he notes, “the ‘best’ cell source for a young child with high-risk leukaemia is probably not the best for a 40 years or older patient with a different type of leukaemia.” Therefore, the experience and selection team from the registers and the transplantation team play a crucial role in ensuring that “the patient has the best chance not only of survival but also of not having complications such as graft-versus-host disease and relapse,” where there is still much to learn to make every transplant successful.

Although less commonly discussed or used in the UK, cord blood stem cells serve as a crucial alternative when a suitable stem cell donor cannot be found or when a donor match is unsuccessful. This was the case for active runner, squash and pickleball player Ruth Wake from Staffordshire, who received her AML diagnosis after a routine annual health screening from her employer. “Needless to say, I was speechless. I was running on the Saturday and was diagnosed the week after. I had no symptoms and no idea that I had a life-threatening disease.” After her chemotherapy, Ruth was told she would need a stem cell transplant to keep her in remission, and four potential stem cell donor matches were found. But further tests ruled them out, a time that Ruth describes as her ‘all time low’. But she was then offered stem cells from a cord blood donation, which she had never heard of. At the time of publishing this blog, Ruth is recovering from her successful transplant.  

The power of positivity: Ruth’s story – Leukaemia UK 

Conclusion

Cord blood transplants (CBT) offer a promising but currently underutilized option for treating blood cancers in the UK. While challenges exist, ongoing research and advancements in technology are improving the effectiveness and accessibility of CBT. These developments position cord blood transplants alongside established treatments like stem cell transplants, with emerging potential for innovations such as lab-grown stem cells. As our understanding deepens and our technologies advance, CBT could become a more widely adopted choice, particularly for patients unable to receive traditional stem cell donations, ultimately strengthening our resources in the fight against leukaemia.

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References:

(i) https://www.ons.gov.uk/peoplepopulationandcommunity/birthsdeathsandmarriages/livebirths/bulletins/birthcharacteristicsinenglandandwales/2021 Accessed 27/08/2024

(ii) Metheny L, Caimi P, de Lima M. Cord Blood Transplantation: Can We Make it Better? Front Oncol. 2013 Sep 17;3:238. doi: 10.3389/fonc.2013.00238. PMID: 24062989; PMCID: PMC3774998.

(iii) https://celltrials.org/maps-cell-and-gene-therapy/percentage-of-births-banking-cord-blood/ Accessed 07/08/2024

(iv) https://www.nhsbt.nhs.uk/cord-blood-bank/donate/where-can-you-donate/ Accessed 08/08/2024