Late Effects of the Immune System
Surgical or functional splenectomy increases risk of life-threatening invasive bacterial infection. Although staging laparotomy is no longer standard practice for pediatric Hodgkin lymphoma, patients from earlier time periods have ongoing risks.[2,3] In addition, children may be rendered asplenic by radiation therapy to the spleen in doses greater than 30 Gy.[4,5] Low-dose involved-field radiation (21 Gy) combined with multiagent chemotherapy did not appear to adversely affect splenic function as measured by pitted red blood cell assays. No other studies of immune status after radiation therapy are available. Functional asplenia (with Howell Jolly bodies, reduced splenic size and blood flow) after bone marrow transplantation has been attributed to graft-versus-host disease.
A pneumococcal vaccine booster is recommended for patients aged 10 years and older and more than 5 years after previous dose. Asplenic patients should also be immunized against Neisseria meningitidis and Haemophilus influenzae type B and should receive antibiotic prophylaxis for dental work.
Prophylactic antibiotics (penicillin or similar broad-spectrum agent) have been recommended for at least 2 to 3 years after splenectomy and until at least 5 years of age for young children. Randomized studies that address the benefit of daily prophylactic antibiotics have not been conducted in a pediatric oncology population; thus, these recommendations are based on extrapolated study data derived from other populations with asplenia.[8,9,10,11] The benefit of prolonged antibiotic prophylaxis is also unknown. Many patients, over time, discontinue use of penicillin; consideration should be given to ensuring availability of appropriate antibiotics for use at the first onset of febrile illness in patients who are not on daily prophylaxis. Medical care should be sought promptly for fevers higher than 38.5�C.
Table 7. Spleen Late Effects
GVHD = graft-versus-host disease; HSCT = hematopoietic stem cell transplantation; T = temperature.
|Radiation impacting spleen; splenectomy; HSCT with currently active GVHD
||Asplenia/hyposplenia; overwhelming post-splenectomy sepsis
||Blood cultures during febrile episodes (T >38.5�C); empiric antibiotics
|HSCT with any history of chronic GVHD
|| Immunologic complications (secretory IgA deficiency, hypogammaglobulinemia, decreased B cells, T cell dysfunction, chronic infections [e.g., conjunctivitis, sinusitis, and bronchitis associated with chronic GVHD])
||History: chronic conjunctivitis, chronic sinusitis, chronic bronchitis, recurrent or unusual infections, sepsis
|Exam: attention to eyes, nose/sinuses, and lungs
Refer to the Centers for Disease Control and Prevention (CDC) Guidelines for Preventing Opportunistic Infections Among Hematopoietic Stem Cell Transplant Recipients for more information on posttransplant immunization.
Although the immune system appears to recover from the effects of active chemotherapy and radiation, there is some evidence that lymphoid subsets may not always normalize. Innate immunity, thymopoiesis, and DNA damage responses to radiation were shown to be abnormal in survivors of childhood leukemia. Antibody levels to previous vaccinations are also reduced in patients off therapy for acute lymphoblastic leukemia for at least one year,[13,14] suggesting persistence of abnormal humoral immunity  and a need for revaccination in such children. Immune status is also compromised after stem cell transplantation, particularly in association with graft-versus-host disease. Follow-up recommendations for transplant recipients have been published by the major North American and European transplant groups, the Centers for Disease Control and Prevention (CDC), and the Infectious Diseases Society of America.[17,18]