Using MS-MLPA as an efficient screening tool for detecting 9p21 abnormalities in pediatric acute lymphoblastic leukemia.

BACKGROUND: Characterization of recurrent genetic lesions in childhood acute lymphoblastic leukemia (ALL) has enabled therapeutic stratification with improved outcomes. The tumor suppressor genes, CDKN2A and CDKN2B, encoding p16(INK4a) , p14(ARF) , and p15(INK4b) have been localized to 9p21. Abnormalities of 9p21 have been reported in 10-30% of childhood ALL using conventional cytogenetics and fluorescence in situ hybridization (FISH). The incidence of 9p21 using more sensitive techniques, such as methylation specific multiplex ligation-dependent probe amplification (MS-MLPA), remains uncertain, and thus also the prognostic significance. PROCEDURE: We investigated the incidence and prognostic importance of 9p21 abnormalities in pediatric ALL patients using MS-MLPA and compared these results to FISH. RESULTS: In total, MS-MLPA or FISH detected aberrations (both dosage and methylation abnormalities) at 9p21 in a remarkable 32/48 (67%) patients in contrast to a much lower rate of only 8% of patients identified to have deletions by standard G banding cytogenetics. MS-MLPA identified five deletions not found by FISH. Aberrant methylation at CDKN2B was found in 19 (46%) patients. 9p21 abnormalities were associated with National Cancer Institute (NCI) high-risk criteria (P = 0.04) and were present in all five patients with T-cell disease. Four pre-B-cell ALL patients relapsed, three of whom had prior 9p21 abnormalities. CONCLUSIONS: MS-MLPA had a higher detection rate for 9p21 abnormalities than previously reported for other techniques. Given the ease of processing, minimal equipment and low cost of MS-MLPA, our results suggest that previous reports may have underestimated the true frequency of 9p21 abnormalities and their potential impact upon ALL outcome.

The impact of prophylactic fresh-frozen plasma and cryoprecipitate on the incidence of central nervous system thrombosis and hemorrhage in children with acute lymphoblastic leukemia receiving asparaginase.

Asparaginase (ASP) therapy is associated with depletion of antithrombin (AT) and fibrinogen (FG). Potential toxicities include central nervous system thrombosis (CNST) and hemorrhage. Historical practice at the Izaak Walton Killam Health Centre (IWK) involves measuring AT and FG levels after ASP administration and transfusing fresh-frozen plasma (FFP) or cryoprecipitate (CRY) to prevent thrombotic and hemorrhagic complications. To determine whether this reduced these complications in children with acute lymphoblastic leukemia (ALL), incidence, outcome, and clinical characteristics of ASP-related CNST in ALL patients at IWK were compared with a similar cohort from BC Children's Hospital (BCCH), where prophylaxis was not performed. Costs associated with preventative versus expectant management were estimated. From 1990 to 2005, 240 patients were treated at IWK and 479 at BCCH. Seven BCCH patients developed venous CNST (1.5%), compared with none at IWK. CNST occurred exclusively during induction. Six patients received anticoagulation and continued ASP. All 7 patients remain in remission. National Cancer Institute high-risk ALL predicted CNST risk (P = .02), whereas sex, age, race, and body mass index did not. Neither FFP nor CRY protected against CNST, suggesting prophylaxis is unwarranted for unselected ALL patients. However, prophylactic replacement for HR patients in induction may be cost-effective.

Routine bone marrow examination in the initial evaluation of paediatric Hodgkin lymphoma: the Canadian perspective.

Bone marrow examination (BME) in paediatric Hodgkin lymphoma (HL) was evaluated, as evidence from adult HL suggests it may be unnecessary. An internet-based survey was used to examine the practice of Canadian paediatric oncologists regarding BME in children and the impact of routine BME was evaluated in patients with HL treated at our institution. Sixteen of 17 paediatric oncology centres were represented. Forty-three percent of eligible doctors completed the survey. Routine BME for stages III and IV disease was consistent nationally. By contrast, 54% and 70% of respondents reported performing routine BME for stages I and II HL respectively. Respondents were more likely to report performing routine BME in low-stage HL if trained outside Canada (P = 0.04, stage I; P = 0.07, stage II) or practicing at smaller centres (P = 0.05, stage I; P = 0.03, stage II). At our institution, 62 patients were eligible for analysis. Only four patients (6.5%) had a positive BME. Anaemia was the only significant risk factor (P = 0.006). No patient with otherwise low stage was found to have marrow involvement. Comparison of staging with and without BME demonstrated no significant difference to final risk classification. BME in paediatric patients with low-stage HL has extremely low yield and may be unnecessary.

Osteoporosis at presentation of childhood ALL: management with pamidronate.

Vertebral fractures at diagnosis of childhood acute lymphoblastic leukemia (ALL) are an uncommon but recognized problem. Clinical issues associated with pathological fractures in these children include pain control and the potential for further treatment-associated fractures and long-term bony morbidity. The authors report the successful use of pamidronate in two children who presented with vertebral compression fractures at diagnosis of ALL. Both patients had pain and low bone mineral density at baseline. In addition to standard chemotherapy, pamidronate (1 mg/kg, IV) was given bimonthly. Initial rapid symptom relief and gradual improvement of bone mineral density was demonstrated in both patients.

CT-estimated volume of Wilms tumor can predict weight.

Wilms tumor weight was used to recruit patients in a recent National Wilms Tumor Study (NWTS) group trial. The authors hypothesized that a simple calculation of tumor volume based on a preoperative CT scan could predict tumor weight. The authors reviewed charts and CT images of patients with Wilms tumors who were treated at their institution between 1985 and 2002. Tumor volume was calculated as: V = 1/6pi x d (long axis) x d (short axis) x d (craniocaudal). Weight and calculated tumor volume were correlated using linear regression. Complete data of tumor weight and volume could be determined in 25 of the 49 patients. These were highly correlated (Spearman R = 0.97). Wilms tumor weight can be predicted based on a simple estimate of tumor volume on a preoperative CT scan. CT-estimated volume may replace weight as a prognostic factor and in guiding management.

Acute myelogenous leukemia and glycogen storage disease 1b.

Glycogen storage disease 1b (GSD 1b) is caused by a deficiency of glucose-6-phosphate translocase and the intracellular accumulation of glycogen. The disease presents with failure to thrive, hepatomegaly, hypoglycemia, lactic acidosis, as well as neutropenia causing increased susceptibility to pyogenic infections. We present a case of a young woman with GSD 1b who developed acute myelogenous leukemia while on long-term granulocyte colony-stimulating factor therapy. The presence of two rare diseases in a single patient raises suspicion that GSD 1b and acute myelogenous leukemia are linked. Surveillance for acute myelogenous leukemia should become part of the long-term follow-up for GSD 1b.