Tumor lysis syndrome results from rapid breakdown of malignant cells, resulting in a number of metabolic abnormalities, most notably hyperuricemia, hyperkalemia, and hyperphosphatemia. Hyperhydration and allopurinol or rasburicase (urate oxidase) are essential components of therapy in all patients except those with the most limited disease.[13,14,15,16,17] An initial prephase consisting of low-dose cyclophosphamide and vincristine does not obviate the need for allopurinol or rasburicase and hydration. Gastrointestinal bleeding, obstruction, and (rarely) perforation may occur. Hyperuricemia and tumor lysis syndrome, particularly when associated with ureteral obstruction, frequently result in life-threatening complications. Patients with NHL should be managed only in institutions having pediatric tertiary care facilities.
Role of Radiographic Imaging in Childhood NHL
Radiographic imaging is essential in the staging of patients with NHL. Ultrasound may be the preferred method for assessment of an abdominal mass, but CT scan and, more recently, magnetic resonance imaging (MRI) have been used for staging. Radionucleotide bone scans should be considered for patients where bone involvement is suspected.
The role of functional imaging in pediatric NHL is controversial. Gallium scans have been replaced by fluorodeoxyglucose positron emission tomography (PET) scanning, which is now routinely performed at many centers. A review of the revised International Workshop Criteria comparing CT imaging alone or CT together with PET imaging demonstrated that the combination of CT and PET imaging was more accurate than CT imaging alone.[19,20] While the International Harmonization Project for PET (now called the International Working Group) response criteria have been attempted in adults, they have yet to be evaluated in pediatric populations.[18,21] This International Working Group has updated their response criteria for malignant lymphoma to include PET, immunohistochemistry, and flow cytometry data.
The value of PET scanning for staging pediatric NHL is under investigation. Data support that PET identifies more abnormalities than CT scanning, but it is unclear whether this should be used to change therapy.
The use of PET to assess rapidity of response to therapy appears to have prognostic value in Hodgkin lymphoma and some types of NHL observed in adult patients, and this is also under investigation in pediatric NHL. However, there are no data in pediatric NHL to support the hypothesis that early response to therapy assessed by PET has prognostic value.