Dr Deepak George Consultant Medical Oncologist and BMT Physician, Apollo Proton Cancer Centre, Chennai

For a patient waiting for a stem cell transplant, finding a suitable donor can be a race against time. In India, this challenge is made more complex by the country’s large and diverse population. The issue is not simply whether enough people have registered as stem cell donors, but whether donor registries adequately represent the communities from which patients come.

For patients with high- and intermediate-risk leukaemias, bone marrow failure syndromes and several inherited blood disorders, allogeneic haematopoietic stem cell transplantation (HSCT) can offer long-term disease control and, in selected cases, the possibility of cure. Before transplantation can take place, however, clinicians must identify a suitable donor, with human leukocyte antigen (HLA) matching playing a central role in donor selection.

Some patients have a suitably matched sibling, but many others require an unrelated or alternative donor. Here, the diversity of the Indian population becomes particularly important. HLA genes are highly polymorphic (diverse) and their distribution varies in different populations. The Indian population has evolved over generations due to geography, migration, ancestry, language, community structures and marriage patterns within communities. These factors lead to considerable variation in HLA alleles and haplotypes between different population groups. The chances of finding a suitable unrelated donor may therefore vary in different communities.

This means India’s stem cell donor challenge is not simply a question of quantity. It is also a question of representation. A registry may continue to grow in absolute numbers while particular population groups remain under-represented. For a patient belonging to one of these groups, a large registry may not necessarily translate into a proportionately higher chance of finding a suitable donor.
Recent research is beginning to demonstrate the scale of this challenge.

A 2025 study of HLA data from more than 130,000 registered Indian stem cell donors revealed distinct patterns of alleles and haplotypes in Indian populations and the need for greater geographic diversity in donor recruitment.

A 2026 analysis involving more than 30,000 Indian cord-blood samples also demonstrated substantial regional and sub-regional HLA diversity and suggested that genetically diverse populations may require considerably larger donor pools to achieve adequate matching probabilities.

Another 2026 analysis of more than 550,000 donors registered with DATRI across 18 Indian regions identified 57,959 HLA haplotypes. Only 202 haplotypes were identified across all 18 regions. These findings reinforce an important point: building a donor registry is not only about increasing its size; it is also about ensuring that its composition reflects the population it is intended to serve.

This has implications for how donor recruitment is planned. Large cities have naturally become important centres for registration drives because they provide access to large populations through hospitals, educational institutions, workplaces and organised campaigns. However, India’s population is highly mobile, and many people living in metropolitan cities have family or ancestral roots in other parts of the country.

This allows for a more targeted approach. In addition to national campaigns, registry data could be used to identify geographical and population gaps and to focus additional registration efforts on underrepresented regions and communities. Such an approach would complement, rather than replace, broad-based donor recruitment.

Every eligible donor has the potential to help a patient, but greater representation across India’s population can increase the diversity of HLA profiles available when an unrelated donor search is required.

Recruitment is only one part of the equation. Donor retention and continued contactability are equally important. A person who registers today may be approached months or years later if identified as a potential match. They may then need to undergo additional testing and medical evaluation before donation.

Potential donors therefore need accurate information about the donation process, its safety and the importance of remaining available and contactable after registration. Public awareness should address common misconceptions and help people understand that registration can eventually have a direct impact on another person’s treatment.

At the same time, developments in transplantation have expanded the options available to patients who do not have a conventional matched donor.

Haploidentical transplantation has become an important option for patients who do not have a suitable matched sibling or unrelated donor. A haploidentical donor is a donor who shares about half of the recipient’s HLA markers and can usually be found within the immediate family, including a parent, child or sibling. The increasing use of this approach has been supported by advances in conditioning, immunosuppression and post-transplant care. Cord-blood transplantation is also an option in selected patients, although its role in adults has changed with the increasing use of haploidentical transplantation. The suitability of cord blood depends on factors including cell dose, engraftment considerations and the patient’s clinical condition.

The field is also addressing more complex immunological barriers. In selected patients undergoing haploidentical transplantation, donor-specific antibodies can complicate donor selection. Where clinically appropriate, strategies such as desensitisation may be considered.

These developments are important because the best transplant strategy is not always about waiting for the most closely matched unrelated donor. The decision must take into account the patient’s disease, disease status, urgency, overall condition, available donors and the experience of the transplant team.

For patients with aggressive blood cancers, prolonged donor searches can have clinical implications. Disease may progress while the search continues, or a patient’s response to treatment may change. Alternative donor approaches can therefore provide important options when a conventional donor cannot be identified within an appropriate timeframe.

International registries also have an important role. Indian-origin populations are represented in donor registries outside the country, and these databases can sometimes provide potential unrelated donors for Indian patients. This is particularly valuable because no single national registry can capture every HLA profile found within a highly diverse population.

However, international collaboration should complement, rather than substitute for, efforts to strengthen domestic donor registries. Availability, compatibility and logistics can all influence whether an international donor identified through a search can ultimately proceed with donation.
India’s scale provides a significant opportunity to build a stronger domestic donor ecosystem. This will require greater use of data to understand where representation gaps exist and where recruitment could have the greatest impact.

Healthcare institutions, donor registries, clinicians, educational institutions, employers and community organisations can all contribute. Recruitment campaigns can move beyond occasional awareness events towards sustained engagement, particularly in regions and populations where donor representation remains lower.

The larger objective is to ensure that the absence of a matched sibling does not automatically mean the absence of a transplant option. Unrelated donor registries, international networks and alternative donor strategies have already expanded the choices available to patients. But the ability to find an unrelated donor can still be influenced by how well a patient’s HLA characteristics are represented in donor databases.

India’s genetic diversity should therefore be viewed not only as a challenge but also as an opportunity to build a more inclusive transplant system. Every additional donor adds to the pool, while greater representation across different populations increases the range of HLA profiles available to patients.
The goal should not simply be to create the world’s largest stem cell donor registry. It should be to create a registry that gives patients from India’s many communities a meaningful opportunity to find a suitable donor when they need one.

For a patient with a potentially life-threatening blood disorder, the difference between a registry that is simply large and one that is genuinely representative can be significant. Building that representation will require wider donor recruitment, targeted outreach, sustained donor engagement and continued collaboration with international registries.

At the same time, continued advances in haploidentical transplantation and other alternative-donor approaches can help reduce dependence on finding a conventional matched unrelated donor.
India’s next step should therefore be to move beyond a numbers-driven approach to donor recruitment and focus on building a donor pool that reflects the country’s diversity, while ensuring that clinicians have multiple options when a conventional match cannot be found.

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