Life's Stem
Stem cell transplantation is changing the way we treat patients, and more importantly… saving lives
By Sheila R. Alcantara, MD
Talk of stem cells instantly sparks a lot of interest, especially with the prospect of the use of these undifferentiated cells for a myriad of research and clinical applications. As these are an amazing repertoire of cells capable of developing into specialized cells, such as the memory cells of the brain or the beating muscle cells of the heart, these serve as potential sources of renewable cells that can be used to treat injury and disease. Called "cell-based therapies," these offer new hope for cure of such elusive diseases as Parkinson's, Alzheimer's, diabetes, and heart disease.
It is important to note, however, that there are two types of stem cells: embryonic and adult (or somatic) stem cells. Much controversy lies on the use of embryonic stem cells, as these are derived from human embryos produced via in vitro fertilization and later donated for research purposes with the informed consent of the donor. These cells can then give rise to all the cells that make up a mature organism.
Adult or somatic stem cells, on the other hand, are undeveloped cells found in adult tissues or organs, where they are primarily involved in maintenance and repair. Today, scientists are only beginning to discover the actual multitude of sites in the body where these can be found.
In contrast, stem cells from the bone marrow have long been established as the precursors of the cellular components of the blood-the all-too important agents that carry oxygen, induce clotting, and help fight infection.
However, it was only in 1968 when the first successful bone marrow transplantation was done at the University of Minnesota. The patient was a child suffering from a devastating infection-prone state called severe combined immunodeficiency syndrome, popularly known as the "bubble boy syndrome."
Cells Beget Cells
Just like the more popular solid organ transplantation such as those of the kidneys and the heart, stem cell transplantation involves the transfer of blood-forming stem cells from a matched donor to the recipient. If stem cells are sourced directly from the bone marrow, it is called bone marrow transplantation (see related story); if it is derived from that portion of blood flowing through blood vessels, it is known as peripheral blood stem cell transplantation. Nowadays, even umbilical cord blood from mother or infant donors may also be used.
The possible sources of these stem cells are varied. However, because the host's immune system mounts an attack on anything that it considers foreign or non-self, it is but logical to look for possible donors from blood relatives, where the chances of getting a match are higher. Nonetheless, only 30 percent of patients needing a stem cell transplant have a suitable donor within the family. Good thing if the patient has an identical twin, an essential clone with the same genetic make-up, in which case it is considered a perfect match. Otherwise, unrelated donors, usually found through national donor programs, would have to be located, or if the patient himself is a suitable source of stem cells, then he can serve his own donor.
How It Works
Blood and marrow transplantation (BMT) works primarily because it restores the normal complement of blood cells-red blood cells, white blood cells, and platelets-which have been depleted or destroyed either by disease or treatment. For instance, in patients with paucity or absence of marrow stem cells characteristic of aplastic anemia, transfer of blood-forming stem cells provides what is lacking, and is therefore curative.
On the other hand, BMT makes it possible for cancer patients to receive very high doses of chemo- or radiotherapy, even at levels that cause bone marrow suppression.
Because the marrow cells that are frequently destroyed during these forms of treatment are also replaced with new blood-forming stem cells, more effective doses can therefore be given. Additionally, the newly transplanted cells can themselves mount an immune attack on the cancer cells, further diminishing their number. Moreover, it also provides cancer-free marrow cells for patients with leukemia, either from a donor, or from the patient after the marrow has been treated to remove leukemic cells.
Where before this mode of treatment was still investigational, today, BMT already serves as the standard form of treatment for a number of diseases associated with abnormalities of the bone marrow or the immune system. The list is long, and even encompasses disorders that were previously considered as incurable. In such cases, BMT may serve as a life-saving procedure.
From Donor to Recipient
The process of transplanting stem cells that will eventually give rise to mature blood cells starts with careful patient selection and evaluation. Serious consideration is given to potential risks and complications, as well as costs and benefits.
Once transplantation has been decided as the best and most appropriate treatment option, the search for a donor, usually first among the siblings, is started, and goes until a donor match is found.
Currently, the process of donor stem cell collection can be done in two ways: either by extracting bone marrow cells from the hip bone, usually done under general anesthesia which puts the donor to sleep, or by harvesting via a special machine called an apheresis machine which separates blood components and returns non-stem cells back to the donor.
Meanwhile, the recipient undergoes a battery of tests, and several days prior to the actual transplantation, is placed under a "conditioning" regimen. This employs chemotherapy or radiation therapy or both, creating "space" for the new stem cells to grow, and at the same time, suppressing the patient's immune system so that rejection does not occur.
Once the stem cells are harvested from the donor, and the recipient is prepared to accept these new cells, transplantation is performed basically just like any other ordinary blood transfusion but through a large vein in the chest. By some exquisite homing process, stem cells travel from the bloodstream to the bone marrow, where it begins the factory that churns out new red and white blood cells and platelets, a process that is called engraftment.
In addition, drugs that prevent the donor stem cells from reacting against host cells, a phenomenon known as Graft-versus-Host Disease (GVHD), are given as well. At this time, patients are extremely vulnerable and prone to infections, and great pains are taken to make sure that patients are always placed in a sterile environment, free of disease-causing microorganisms that can potentially complicate the transplantation process. Patients are closely monitored and once discharged, require regular follow-up.
Local Pioneer
Although BMT has been performed in major centers worldwide since the 1970s, it was not until 1990 that the first stem cell transplantation was done in the Philippines. Dr. Honorata Baylon had just finished her training in bone marrow transplantation from the Fred Hutchinson Cancer Research Center in Seattle, Washington, and was very eager to start it here. She brought back with her all the necessary equipment and supplies, and did the first transplant on a case of aplastic anemia at the National Kidney Institute.
She recalls: "The reason that I wanted to do bone marrow transplant in the country is it is very expensive. If you go abroad, it will cost from US$200,000 to US$300,000. Those Filipinos who have that much money,
sila ang nagpapa-transplant abroad. But what about the majority of Filipinos who could not afford it?"
One month's worth of confinement outside the country translates to a whopping PhP10 to 15 million, and understandably, only a few moneyed local denizens have the fortune to shell out that amount of money.
Here, it is still very expensive, but Dr. Baylon says that we can still bring the cost down. The actual cost depends on the case, and can be anywhere from one to three million pesos, to much less than that. "But the thing is," she reiterates, "once you go for transplant, you should really have the money, because the post-transplant care is still expensive."
Starting from Scratch
Setting up a transplant center is no easy task, and for Dr. Baylon, it was even more difficult because she was alone when she started it. She had to train the nurses and lab personnel, even dietary and housekeeping had to be taught proper transplant care. Now, she is now delighted however, that "we already have a team, and I'm not alone anymore, and fortunately, there are younger doctors who came back from their training abroad."
Although only nine patients have been undergone transplant since the program started more than ten years back, Dr. Baylon is still very optimistic that things can only get better. Last year, they opened another transplant center at St. Luke's and all in all, they were able to do five cases for the year.
Shares the chief stem cell transplant expert in the country: "If you're asking why we can't do that many, it's because of the expense. It's really very costly." She also notes that many people are still not aware or have no belief in the efficacy of the procedure. She also laments the poor support being given these patients. Dr. Baylon, however, believes that in time, stem cell transplants will be as common as bypass surgery, which is now being done left and right. "Dun din kami pupunta," she says with conviction.
Newer Frontiers
It is a long and arduous road towards finally making stem cell transplantation easily accessible, especially to patients who need it most. In the meantime, newer treatment methods are constantly being employed to reduce the financial burden on patients by reducing hospital stay. Moreover, alternative options for patients with no identifiable matches are in the offing, with the advent of haplo-identical transplants, which allow transplantation even with just a 50-percent match.
While so much more still need to be done, there is still hope that one day, every person who needs a transplant may be able to avail himself of this life-saving procedure. But until then, this country, and all its systems, will have to start doing its part in sharing the burden. There is no other recourse.
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