Background

PBPC mobilization, or autologous peripheral blood progenitor cell mobilization is a process through which several stem cells in the bloodstream are harvested for collection and transplant, leading to a higher yield. This procedure is beneficial for patients that are to receive high-dose chemotherapy which eradicates not only cancerous but also healthy bone marrow cells. The mobilized stem cells can then be collected, sometimes stored, and can again be given back to the patient to replenish the damaged bone marrow and normalize blood cell formation. 

Indications

• Non-Hodgkin Lymphoma (NHL): Some patients with aggressive types of NHL can be mobilized for PBPC during their therapy course. 
• Hodgkin Lymphoma: PBPC collection can be done in relapsed or refractory HL as a treatment option for the patients. 
• Multiple Sclerosis (MS): Recent and current approaches in molecular medicine have described autologous PBPC transplantation and cases of severe, refractory MS. 
• AL Amyloidosis: PBPC mobilization and transplantation utilizable in AL amyloidosis patients. 

Contraindications

• Bone Marrow or Blood Disorders:  These are aplastic anemia, myelodysplastic syndromes or certain types of leukemia. 
• Infections: Malignancies can also be contraindications because the active infection could spread to other people, or the patient’s health status could worsen during mobility. 
• Recent Bleeding or Clotting Disorders: During mobilization there is a possibility of complications for patients who have histories of recent bleeding episodes, low platelet counts and thromboembolic events. 

Outcomes

Equipment

• Apheresis Machine 
• Centrifuge 
• Blood Collection Set and Tubing 
• Freezer/Storage Units 
• Cell Counter/Analyzer 
• Sterile Processing Equipment 
• Laboratory Reagents and Consumables 
• Patient Monitoring Equipment 
• Portable Infusion Pumps 

Patient Preparation

Pre-Collection Evaluation 

• Medical History and Physical Examination: An extensive history is taken of the patient, and a physical examination is performed to evaluate the patient’s general state of health and their ability to undergo the procedure. 
• Laboratory Tests: Complete blood count, liver and kidney function and infectious diseases screens are recorded. 
• Bone Marrow Assessment: Rarely, if the physician feels it is necessary, they may suggest a bone marrow biopsy to determine the functioning of the bone marrow of a specific disease. 

Technique

Step 1-Pre-Mobilization Evaluation: 

Medical Assessment: Assess the patient’s general well-being, disease, and the possibility of stem cell harvesting. 

Blood Tests: The confirmed checklist would include CBC, renal function, liver function, and serologic markers of various infections. 

Step 2-Mobilization Regimen: 

Administer hematopoietic growth factors e.g. granulocyte colony stimulating factor (G-CSF) like filgrastim to mobilize stem cells from the bone marrow to the peripheral blood. 

G-CSF is administered at 10 µg/kg/day subcutaneously for 4-5 days. 

Although in some instances it has been used in conjunction with growth factors, the primary goal is to augment the procedure of mobilization. 

Cyclophosphamide combined with G-CSF is one of the most frequently used. 

Step 3-Monitoring: 

Blood Counts: The following tests should be conducted; the daily white blood cell (WBC) count will determine the response to mobilization. 

CD34+ Cell Count: Additionally, the number of CD34+ cells in the peripheral blood can be quantified to define the collection time. This is usually done by flow cytometry. 

Step 4-Apheresis (Stem Cell Collection): 

Perform apheresis to collect stem cells for the individuals. Some amount of blood is taken through the vein and is centrifuged to separate the stem cells and the rest of the components are given back to the body of a patient. 

Often, several sessions are required to obtain the necessary number of cells. Patient specific threshold is recommended to be at least 2-5 x 10^6 CD34+ cells per kilogram of the patient’s weight. 

Step 5-Post-Collection Processing: 

After collection they go through a processing, counting and the stem cells are cryopreserved means they are frozen for use in future. 

Carry out viability and sterility test on the cells that has been collected. 

Step 6-Post-Mobilization Care: 

Monitor Side Effects: They have other side effects like bone pain, headache, and fatigue when patients are administered with G-CSF. This modality of treatment also leads to other side effects like vomiting, nausea, and hair loss. 

Supportive Care: Comfort measures and pain control, as appropriate and desired by the patient, should be maintained. 

Step 7-Transplantation: 

Before the stem cells are infused back into the patient, the patient may first receive a treatment as a conditioning regimen, this is often in the form of high dose chemotherapy and or radiation to eliminate any residual tumors as well as make space for the new stem cells. 

The stem cells that have undergone the process of cryopreservation are re-introduced back to the patient through the intravenous method. 

Complications

Hematologic Complications: 

• Thrombocytopenia: Mobilization agents can also lower platelets count hence predisposing the patient to bleeding especially in the immediate period after the agent’s administration. 
• Leukocytosis: Leukocytosis resulting from using growth factors can present with headache, bone pain, or splenomegaly. 

Infectious Complications: 

• Febrile Neutropenia: Low neutrophil count may cause fever to patients thus exposing them to more risks of infections. 
• Infections: Central venous catheters are commonly used for apheresis which can make the patients more likely to be susceptible to bloodstream infections as compared to the single needle puncture technique. 

Cardiovascular Complications: 

• Thrombosis: Since the levels of circulating white blood cells are high, blood clots are likely to form in the bloodstream. 
• Cardiac Events: Some patients, especially those with pre-existing cardiac conditions, might experience heart-related issues due to stress from the mobilization agents. 
• Bone Pain: This one is rather frequent due to the enlargement of this cavity because of the proliferation of bone marrow; the condition is treated with painkillers. 

References

Peripheral blood progenitor cell mobilization for autologous and allogeneic hematopoietic cell transplantation: guidelines from the American Society for Blood and Marrow Transplantation – PubMed (nih.gov)

References

Peripheral blood progenitor cell mobilization for autologous and allogeneic hematopoietic cell transplantation: guidelines from the American Society for Blood and Marrow Transplantation – PubMed (nih.gov)