Results from a first-time analysis comparing toxicity experienced by bone marrow stem cell donors and peripheral blood stem cell (PBSC) donors suggest that a donor’s age, weight, or gender can affect the intensity and duration of their post-donation side effects.

Study results are published in Blood, the Journal of the American Society of Hematology (ASH).

Haematopoietic, or blood-forming, stem cells (HSCs) are found in the bone marrow, the blood stream (known as peripheral blood stem cells or PBSCs), and in umbilical cord blood.

HSCs can be collected from a donor through a surgical procedure in which liquid bone marrow is extracted from the pelvic bone, or in a nonsurgical procedure during which HSCs are directed from the bone marrow into the blood stream where they can be collected through a blood filtering process called apheresis.

While both methods of HSC procurement have been considered to be safe, many prospective donors remain fearful of the risk of pain and long recovery times that may accompany the donation process, contributing to an overall donor shortage.

According to the National Marrow Donor Program^® (NMDP), which operates Be The Match^®, each year approximately 10,000 patients in the United States with leukaemia, lymphoma, and other life-threatening blood cancers need a HSC transplant from an unrelated donor, but only half receive one.

In recent years, the NMDP has worked to ensure that HSC donations are performed safely and ethically to minimise donor discomfort. In the late 1990s, the NMDP created tools to assess adverse events encountered by PBSC donors during and after donation and have since published detailed PBSC side effect reports in the scientific literature.

While this information was later adapted for bone marrow donors, until recently no formal analysis had been completed directly comparing side effects encountered by those donating bone marrow stem cells with those donating PBSCs.

“Potential donors and their physicians need to know the risks of bone marrow and PBSC donation, and to this point we have not been able to draw clear distinctions between the two donation methods. Recognising this need, we designed our study to prospectively compare the experiences of unrelated bone marrow and PBSC donors to gain a better understanding of what donors experience throughout the donation process,” said Michael A. Pulsipher, MD, the study’s first author, Professor of Paediatrics and Medicine at the University of Utah, and Medical Director of the Pediatric Blood and Marrow Transplant Program at Primary Children’s Medical Center.

In the study, Dr. Pulsipher and his research team assessed 2,726 bone marrow and 6,768 PBSC donors whose HSC collection was facilitated by the NMDP between 2004 and 2009.

Bone marrow collection was conducted by 164 donor centers and PBSC donation was facilitated by 174 donor and apheresis centers. Donor and collection centers performed donor medical evaluations the day of marrow or PBSC collection, then followed up at two days and one week post-donation, with weekly contact until full recovery.

One-month, six-month, and annual assessments were also made to determine the presence of any new or residual symptoms, as well as to capture any toxicity the donor may have experienced.

Researchers observed that 43 percent of bone marrow donors and 15 percent of PBSC donors reported at least one side effect one week after donation, with fatigue and insomnia being the most commonly reported side effects in both donor types. At one month follow-up, the percentage of both types of donors reporting side effects had returned to their “normal state,” or levels that the donors had reported prior to beginning the donation process.

A very small percentage of bone marrow donors (less than 3%) reported mild discomfort at their donation site for a few months after donation.

While pain and other side effects were found to be generally comparable among bone marrow and PBSC donors, Dr. Pulsipher’s research team found differences in toxicity experienced by the two donor groups when they analyzed data by donor body mass index (BMI), age, and gender.

Among overweight (BMI of 25-29.9) and obese donors (BMI over 30), PBSC donors were more likely than bone marrow donors to document moderate-severe (grade 2) pain levels; however, weight did not factor in the prevalence of fatigue and other toxicities between the two donor groups.

Regardless of donation process, donors between ages 50-60 were actually at a lower risk than younger donors of experiencing moderate pain around the time of donation, but at a higher risk of persistent pain one week after bone marrow or PBSC collection. In addition, older donors were at an increased risk of severe and persistent side effects and fatigue at one week post donation, reflecting a slower recovery period after completion of the donation.

Among both bone marrow stem cell and PBSC donors, women were more likely than men to experience pain and fatigue during and after donation, and they were twice as likely to require hospitalization, although the need for non-routine hospitalization was rare (approximately 1%).

“Our study data not only show that both methods of hematopoietic stem cell donation are safe, they also more clearly define who may be at the most risk for potential complications following donation, allowing collection centers to develop approaches to further increase safety for donors at higher risk,” said Dr. Pulsipher. “More importantly, we hope that our results help convince healthy, potential donors who may have previously had doubts or anxieties about the process that becoming a stem cell donor is a safe and effective way to help save a life.

Source: ASH