Susan Picton

Novel PMS2 Pseudogenes Can Conceal Recessive Mutations Causing a Distinctive Childhood Cancer Syndrome

We investigated a family with an autosomal recessive syndrome of cafe-au-lait patches and childhood malignancy, notably supratentorial primitive neuroectodermal tumor. There was no cancer predisposition in heterozygotes; nor was there bowel cancer in any individual. However, autozygosity mapping indicated linkage to a region of 7p22 surrounding the PMS2 mismatch-repair gene. Sequencing of genomic PCR products initially failed to identify a PMS2 mutation. Genome searches then revealed a previously unrecognized PMS2 pseudogene, corresponding to exons 9-15, within a 100-kb inverted duplication situated 600 kb centromeric from PMS2 itself. This information allowed a redesigned sequence analysis, identifying a homozygous mutation (R802X) in PMS2 exon 14. Furthermore, in the family with Turcot syndrome, in which the first inherited PMS2 mutation (R134X) was described, a further truncating mutation was identified on the other allele, in exon 13. Further whole-genome analysis shows that the complexity of PMS2 pseudogenes is greater than appreciated and may have hindered previous mutation studies. Several previously reported PMS2 polymorphisms are, in fact, pseudogene sequence variants. Although PMS2 mutations may be rare in colorectal cancer, they appear, for the most part, to behave as recessive traits. For technical reasons, their involvement in childhood cancer, particularly in primitive neuroectodermal tumor, may have been underestimated.

A multivariate analysis of factors determining tumor progression in childhood low-grade glioma: a population-based cohort study (CCLG CNS9702)

The purpose of this study was to identify risk factors for the progression of low-grade glioma in children from a large population-based cohort. Patient and tumor details of a national cohort of children with low-grade glioma, recruited into an international multidisciplinary clinical strategy, were subjected to univariate and multivariate analyses of progression-free survival and overall survival. From the cohort of 798 patients, 639 patients were eligible, with a median age 6.71 years (0.26-16.75 years); 49% were males; 15.9% had neurofibromatosis type 1, 63.7% pilocytic astrocytoma, 5.9% fibrillary astrocytoma, 4.2% mixed neuronal-glial tumors, and 3.6% others; 21.1% were diagnosed clinically. Anatomically implicated were 31.6% cerebellum, 24.6% chiasma/hypothalamus, 16.0% cerebral hemispheres, 9.9% brain stem, 6.1% other supratentorial midline structures, 5.9% optic nerve only, 4.5% spinal cord, and 1.4% others. The 5-year overall survival and progression-free survival in the whole cohort were 94.6% and 69.4%, respectively. There was a significant association between age and site (P < .001) and extent of tumor resection and site (P < .001). Multivariate analysis identified young age, fibrillary astrocytoma, and extent of surgical resection as significant independent risk factors for progression. Hypothalamic/chiasmatic tumors demonstrated the most sustained tendency to progress. In conclusion, the influence of age and anatomical site upon the risk of tumor progression suggests that these factors strongly influence tumor behavior for the majority of pilocytic tumors. Age <1 year and 1-5 years, fibrillary histology, completeness of resection, and chiasmatic location are candidates for stratification in future studies.

Renal medullary carcinoma: Prolonged remission with chemotherapy, immunohistochemical characterisation and evidence of bcr/abl rearrangement

BACKGROUND Renal medullary carcinoma (RMC), an extremely rare tumour of the kidney, carries a dismal prognosis, with no reports to date of significant response to chemotherapy or radiotherapy. A case of this tumour in a male child, who showed a dramatic response to chemotherapy, is described. PROCEDURE A detailed histological evaluation of the tumour and cytogenetic analysis using fluorescent in situ hybridisation (FISH) was carried out. The child was treated with multiagent chemotherapy, followed by abdominal radiotherapy. RESULTS A detailed histopathological and immunohistochemical portrait of this tumour is described, and FISH studies confirmed the presence of a bcr/abl rearrangement. The child obtained complete radiological remission following chemotherapy, although he later relapsed and died of progressive disease despite further attempts at treatment with chemotherapy. CONCLUSIONS Although there are no previous reports of response of this tumour to chemotherapy, this case illustrates that treatment of this disease is justified. The responses of other cases to similar drug regimens would be of interest to confirm whether the encouraging response described for this case could be reproduced. Cytogenetic analysis of other cases of RMC may clarify whether the abnormalities seen in this case are typical.

Minimal residual disease at the time of peripheral blood stem cell harvest in patients with advanced neuroblastoma.

BACKGROUND Despite treatment with high-dose myeloblative chemotherapy and peripheral blood stem cell (PBSC) rescue, a high proportion of children with neuroblastoma relapse and die. Re-infusion of PBSC contaminated with tumour at the time of autologous transplantation may play a significant role in this relapse. In this study the frequency of tumour contamination in PB from children with neuroblastoma has been investigated. PROCEDURE Minimal residual disease was measured using RT-PCR for tyrosine hydroxylase (TH) mRNA in PBSCs from patients with advanced neuroblastoma. PBSCs from 18 patients in complete clinical remission were studied. RESULTS Studies in other cancers have suggested minimal contamination of PBSCs with tumour cells; TH mRNA was detected by RT-PCR in 50% (9/18) of PBSC harvests. Seventy-seven percent (7/9) of patients with TH mRNA in PBSC died of disease compared to 44% (4/9) who were TH mRNA-negative. CONCLUSIONS Therefore, the presence of TH mRNA in PBSCs appeared to be associated with an unfavourable outcome, although this was not statistically significant. In summary, RT-PCR for TH mRNA is a sensitive method for the identification of tumour cells in PBSC harvest. The presence of TH mRNA in PBSC harvest may reflect disease status and be associated with an unfavourable outcome, although long-term clinical outcome studies in a larger patient cohort are required.

Phase II Trial of Irinotecan in Children With Relapsed or Refractory Rhabdomyosarcoma: A Joint Study of the French Society of Pediatric Oncology and the United Kingdom Children's Cancer Study Group

PURPOSE This phase II study was designed to evaluate the efficacy of irinotecan administered intravenously once every 3 weeks in pediatric patients with recurrent or refractory rhabdomyosarcoma. PATIENTS AND METHODS A total of 35 patients younger than age 20 years, with refractory or relapsed rhabdomyosarcoma for which standard treatments have failed, received irinotecan at 600 mg/m2 administered as a 60-minute infusion every 3 weeks. Concomitant treatments included atropine for cholinergic symptoms, loperamide for diarrhea at the first liquid stool, and preventive antiemetic treatment. Tumor response was assessed every two cycles until progression according to WHO criteria. RESULTS The best overall response rate to irinotecan was 11.4% (95% CI, 3.2 to 26.7%; 2.9% complete responses, 8.5% partial responses) from all patients recruited. The median times to progression and survival were 1.4 and 5.8 months, respectively. A total of 112 cycles were administered, with a median number of two cycles per patient (range, 1 to 16). The most common grade 3/4 toxicities were neutropenia (46%), abdominal pain or cramping (17%), cholinergic syndrome (14%), nausea/vomiting (11%), anemia (11%), thrombocytopenia (9%), and diarrhea (6%). CONCLUSION In heavily pretreated children with a high tumor burden who have been treated with multiagent chemotherapy, irinotecan administered intravenously as a single agent, at 600 mg/m2 every 3 weeks, showed an interesting objective response rate and a good tolerance profile in rhabdomyosarcoma.

A review of the cytogenetics of 58 pediatric brain tumors

We describe the cytogenetic results of 58 pediatric central nervous system (CNS) tumors of variable histology, investigated between 1992 and 2000. Successful cytogenetics were obtained for 53 patients, with clonal chromosome abnormalities demonstrated in 25. Notable findings included (1) 2p abnormality in four primitive neuroectodermal tumors (PNET); (2) 1p loss in four low-grade gliomas and two PNET; (3) telomeric associations in one pilocytic astrocytoma; (4) chromosome 7 gain in four astrocytomas and two PNET; (5) 17p loss in four PNET; (6) double minutes in one PNET and three glioblastomas; and (7) chromosome 10 loss in four PNET. Higher grade tumors demonstrated greater karyotype complexity. Low-grade tumors showed either minimal simple chromosome changes or a normal karyotype. Chromosome abnormalities were more frequent in supratentorial tumors than their infratentorial counterparts. Our results add weight to the limited existing body of cytogenetic documentation for pediatric CNS tumors and provide further evidence that 2p loss is a consistent region of chromosome involvement in PNET. We advocate further studies of CNS tumors, in particular, to evaluate the importance of 2p changes and to compare cytogenetic results for supratentorial tumors and their infratentorial counterparts.

Relapsed intracranial ependymoma in children in the UK: patterns of relapse, survival and therapeutic outcome.

Relapsed ependymoma in children poses difficult dilemmas in management. Clinico-pathological and treatment data of 108 children with relapsed ependymoma in the United Kingdom (UK) treated between 1985 and 2002 were reviewed to identify prognostic factors affecting survival. The primary site was the most common site of relapse (84%). Overall 25% had metastatic relapse. Surgery at relapse was attempted in only 55%. Radiotherapy was delivered at relapse in 66% infants and 50% of older children were re-irradiated. Overall 5-year survival was 24% and 27% for children less than 3 years of age at initial diagnosis and older children, respectively. Multivariate analysis showed that, for infants, surgery (p=0.01) and radiotherapy (p=0.001) at relapse were independent predictors of survival. For older children regardless of the previous radiotherapy, repeat irradiation was associated with better outcome (p=0.05). Relapse was associated with poor outcome in both age groups. A survival advantage conferred by both radiotherapy and surgery at relapse is independently significant.

Diagnosing childhood cancer in primary care - a realistic expectation?

The burden of childhood cancer for Primary Care Trusts (PCTs) is unknown. PCTs in Yorkshire are representative of England and Wales and show little heterogeneity in the incidence rates of childhood cancer. Each PCT will expect three to five newly diagnosed children per year. A single GP is likely to see an incident case once every 20 years.

A systematic review of time to diagnosis in children and young adults with cancer

Purpose It is often assumed that prolonged time to diagnosis (TTD) for cancer negatively influences overall survival and survivorship through advanced stage disease at diagnosis. This systematic review assesses existing early diagnosis research in childhood and young adult cancer and aims to identify whether a consensus exists within the literature in relation to the terminology and methodologies used to investigate TTD in this population. Methods Medline, Embase, the Centre for Reviews and Dissemination database and Cochrane library were searched for papers on children and young adults (0–30 years) published from 1948 to the present. Results Of the 1665 potentially eligible citations identified, 32 papers met the inclusion criteria. The majority of work was in European (n=15) or North American (n=8) populations. Most work focused on brain tumours (n=10), retinoblastomas (n=5) and bone and soft tissue sarcomas (n=4). The majority of studies were in hospital-based settings (n=25), with only seven papers adopting a population-based setting. Summary statistics presented were mostly median TTD, the skewed distribution of the data meant comparisons between studies based on medians were difficult and combining studies within a meta-analysis was not appropriate. Conclusions Within the childhood and young adult population, TTD for cancer varies between diagnostic groups and with age at diagnosis in the majority of studies. In order that clear conclusions can be drawn from early diagnosis research in children and young adults, specific criteria identifying circumstances in which delay has occurred should accompany a defined time line to diagnosis or treatment in every study.

A genome-wide association study identifies susceptibility loci for Wilms tumor

Wilms tumor is the most common renal malignancy of childhood. To identify common variants that confer susceptibility to Wilms tumor, we conducted a genome-wide association study in 757 individuals with Wilms tumor (cases) and 1,879 controls. We evaluated ten SNPs in regions significantly associated at P < 5 × 10−5 in two independent replication series from the UK (769 cases and 2,814 controls) and the United States (719 cases and 1,037 controls). We identified clear significant associations at 2p24 (rs3755132, P = 1.03 × 10−14; rs807624, P = 1.32 × 10−14) and 11q14 (rs790356, P = 4.25 × 10−15). Both regions contain genes that are plausibly related to Wilms tumorigenesis. We also identified candidate association signals at 5q14, 22q12 and Xp22.