Half Identical Stem Cell Transplantation

January 14, 2011

The doctor who introduced half-identical stem cell transplantation to Thailand explains how the new procedure is helping defeat one of the most formidable types of cancer.

Innovative new treatment joins the fight against leukemia

The doctor who introduced half-identical stem cell transplantation to Thailand explains how the new procedure is helping defeat one of the most formidable types of cancer.

There are promising developments to report in the fight against one of the most feared types of cancer. White blood cell cancer, known commonly as leukemia, generates more than its fair share of fear, not only because of its high mortality rate, but also because we still don’t fully understood what causes leukemia nor why people with no apparent risk factors can still develop the disease. 

Advances in technology and medical procedures have led to significant improvements in leukemia treatments in recent years, including the advent of a procedure known as half-identical hematopoietic stem cell transplantation. turned to the hematologist who first introduced the procedure to Thailand, Dr. Wichean Mongkonsritragoon, to find out how this innovative technique is giving new hope to many leukemia patients. 

Understanding leukemia

Leukemia is a cancer of the blood cells that originates in the bone marrow – the soft tissue located inside the bone where blood cellsare produced. Leukemia is characterized by an abnormal increase in white blood cell production which eventually disrupts the healthy production of blood in the bone marrow. The disease produces symptoms including macrocytic anemia, irregular bleeding, painful swelling, and an increased susceptibility to infection, among others. 
Leukemia ranks well behind more prevalent types of cancer overall, but it is still one of the most prevalent of blood-related cancers, on par with lymphoma. And leukemia is known to produce highly intense symptoms that can progress very quickly, leading to a sharp, rapid decline in patient health.  

“There are two main types of leukemia: acute and chronic,” Dr. Wichean explains. “Acute leukemia is more prevalent, and its symptoms usually appear quickly – within one to three months after the onset of the disease. Just a few decades ago, there was no treatment that could effectively cure this type of cancer. But in recent years, treatments have improved greatly; procedures such as stem cell transplantation have led to better outcomes for many acute leukemia patients.” 

Chronic leukemia progresses much more slowly than acute leukemia; it can take several years for the first symptoms of the disease to appear. Chronic leukemia can be diagnosed using a blood test; some cases are identified after a routine check-up reveals some type of blood abnormality associated with leukemia, such as hepatomegaly or splenomegaly.  

Treatment strategies

Devising the best treatment strategy depends largely on each patient’s type of leukemia and individual health situation. Determining the right treatment for a particular patient requires the hematologist to consider  a host of factors and possibilities, as leukemia patients can be more susceptible to complications compared to those being treated for other types of cancer.  

“For patients with acute leukemia, treatment typically begins with a course of chemotherapy to kill leukemia cells in the patient’s blood and bone marrow,” Dr. Wichean explains.
“After chemotherapy, the stem cell transplantation procedure, called bone marrow transplantation in the past, would be performed on patients already approved for the procedure.” Patients who aren’t suitable for transplantation usually undergo chemotherapy with a more powerful medication to boost their chances for a full remission of the disease.
“For chronic leukemia, the traditional treatment protocol began with the standard stem cell transplantation procedure, followed by chemotherapy, with the aim of completely eliminating the leukemia,” Dr. Wichean continues. “Thanks to significant advances in medication in recent years, chemotherapy alone is now the standard treatment for chronic leukemia. While chemotherapy doesn’t permanently wipe out the cancer the way stem cell transplantation can, it offers advantages in terms of better patient safety and higher survival rates among patients with chronic leukemia.”  

One in 40,000

There are two main sources of stem cell donations for transplantation – stem cells can be taken from the patient himself, or the donor can be someone other than the patient. When dealing with leukemia, using a patient’s own stem cells is rarely possible due to thehigh probability thatthe patient's stem cells will contain cancerous cells.

The odds of a donation from a non-relative donor turning out to be an HLA (Human Leukocyte Antigen) match withthe patient are roughly 40,000 to one. In time and expense, finding a matching non-relative donor for a leukemia patient is usually impractical.
Stem cell transplantation using a non-relative donor’s marrow also carries its own set of risks: Transplantation using donated stem cells with a low HLA compatibility score poses a significant risk of rejection – a situation that can produce serious complications including hepatitis, hepatic failure, digestive system disorders, and other life-threatening problems.  

Half-identical transplantation 

“The challenge of finding matching donors was the critical issue that inspired the idea of half-identical stem cell transplantation,” says Dr. Wichean. “Being able to use a donor with a 50 percent HLA match – a patient’s mother, father, children and siblings – is quite compelling.”

Compared to the standard transplantation method, one key difference in half-identical stem cell transplantation is the use of immunosuppressive medication to guard against the possibility of rejection. This requires a great  deal of caution and close monitoring, as the immune system of a leukemia patient is already operating at a less-than-optimal level, making the patient more susceptible to infections and other side effects. 

“The success rate for half-identical transplantation with a family member donor is similar to the normal procedure using an unrelated, but fully matching, donation,” Dr. Wichean notes.“But the half-identical method is a potential option for more patients, because donors are members of the patient’s own family. And while there are of course potential risks involved with the procedure, the dangers posed by the cancer are certainly much greater than the potential treatment risks. Half-identical stem cell transplantation is generating a great deal of interest in the medical community in Thailand and around the world.”

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