Detection of clusters of a rare disease over a large territory: performance of cluster detection methods

International audienceBackgroundFor many years, the detection of clusters has been of great public health interest. Several detection methods have been developed, the most famous of which is the circular scan method. The present study, which was conducted in the context of a rare disease distributed over a large territory (7675 cases registered over 17 years and located in 1895 units), aimed to evaluate the performance of several of the methods in realistic hot-spot cluster situations.MethodsAll the methods considered aim to identify the most likely cluster area, i.e. the zone that maximizes the likelihood ratio function, among a set of cluster candidates. The circular and elliptic scan methods were developed to detect regularly shaped clusters. Four other methods that focus on irregularly shaped clusters were also considered (the flexible scan method, the genetic algorithm method, and the double connected and maximum linkage spatial scan methods). The power of the methods was evaluated via Monte Carlo simulations under 27 alternative scenarios that corresponded to three cluster population sizes (20, 45 and 115 expected cases), three cluster shapes (linear, U-shaped and compact) and three relative risk values (1.5, 2.0 and 3.0).ResultsThree situations emerged from this power study. All the methods failed to detect the smallest clusters with a relative risk lower than 3.0. The power to detect the largest cluster with relative risk of 1.5 was markedly better for all methods, but, at most, half of the true cluster was captured. For other clusters, either large or with the highest relative risk, the standard elliptic scan method appeared to be the best method to detect linear clusters, while the flexible scan method localized the U-shaped clusters more precisely than other methods. Large compact clusters were detected well by all methods, with better results for the circular and elliptic scan methods.ConclusionsThe elliptic scan method and flexible scan method seemed the most able to detect clusters of a rare disease in a large territory. However, the probability of detecting small clusters with relative risk lower than 3.0 remained low with all the methods tested

Epidémiologie descriptive des hémopathies malignes de l'enfant en France métropolitaine

LE KREMLIN-B.- PARIS 11-BU Méd (940432101) / SudocSudocFranceF

[Clinical presentation and epidemiology of childhood Langerhans cell Histiocytosis]

International audienc

Descriptive epidemiology of childhood Langerhans cell histiocytosis in France, 2000-2004.

International audienceINTRODUCTION: Childhood Langerhans cell histiocytosis (LCH) is a rare and poorly understood multisystemic disease. The French National Registry of Childhood Hematopoietic Malignancies (NRCH) has recorded LCH cases of all subtypes since 2000. The present study describes the data on LCH collected on a national scale over a 5-year period. MATERIALS AND METHODS: The cases were children aged less than 15 years, diagnosed with LCH of any type between 2000 and 2004, and residing in mainland France at the time of diagnosis. Completeness was evaluated by capture-recapture after cross-checking against the database compiled by the French Langerhans Cell Histiocytosis Study Group. RESULTS: Two hundred fifty-eight cases of LCH were registered. The completeness of the NRCH was estimated to be 97%. The annual incidence rate was 4.6/10(6) children aged less than 15 years and the sex ratio was 1.2. Bone and skin were the most commonly involved organs at diagnosis. The incidence rate decreased with age from 15.3/10(6) before 1 year to 2.0/10(6) after 10 years. The disease was mainly unifocal (2.6/10(6)) and rarely disseminated (0.6/10(6)), but disseminated forms predominated in infants. The overall 2-year survival rate was 99% (95%CI: [97; 100]). About 30% of the LCH cases were enrolled in a clinical trial at first onset. No case was treated by radiotherapy. CONCLUSION: This study evidenced the main features of LCH incidence in the overall population and was consistent with previous studies. The NRCH thus appears to be a very promising tool for further elucidation of LCH. Pediatr Blood Cancer (c) 2008 Wiley-Liss, Inc

Survival in France after childhood acute leukaemia and non-Hodgkin's lymphoma (1990-2000).

International audienceThis article describes the survival after childhood acute leukaemia (AL) and non-Hodgkin's lymphoma (NHL) of French population aged less than 15 years. The French National Registry of Childhood Leukaemia and Lymphoma recorded 3995 cases of acute lymphoblastic leukaemia (ALL), 812 of acute myeloid leukaemia (AML) and 1137 of NHL over the period from 1990 to 2000. Overall survival rates at 5 years were 82% (95% CI 80-83), 58% (95% CI 54-61) and 87% (95% CI 85-89) for ALL, AML and NHL, respectively. Survival after AL increased from 77% (95% CI 75-80) in 1990-1992 to 85% (95% CI 83-87) in 1997-2000 for ALL and from 47% (95% CI 41-54) to 61% (95% CI 55-67) for AML. Among AL cases, children aged 1-4 years had the most favourable prognosis. Down's syndrome was associated with poor survival after ALL. No gender-related variations in survival were in evidence. The results reported herein are similar to those reported by other European registries and clinical trials

Childhood cancer survival in France, 2000–2008

International audienceThis paper reports the latest survival data for French childhood cancer patients at the national level. Data from the two French National Registries of Childhood Cancer (Haematopoietic Malignancies and Solid Tumours) were used to describe survival outcomes for 15,479 children diagnosed with cancer between 2000 and 2008 in mainland France. The overall survival was 91.7% at 1 year, 86.9% at 2 years and 81.6% at 5 years. Relative survival did not differ from overall survival even for infants. Survival was lower among infants for lymphoblastic leukaemia and astrocytoma, but higher for neuroblastoma. For all cancers considered together, 5-year survival increased from 79.5% in the first (2000-2002) diagnostic period to 83.2% in the last (2006-2008) period. The improvement was significant for leukaemia, both myeloid and lymphoid, central nervous system tumours (ependymoma) and neuroblastoma. The results remained valid in the multivariate analysis, and, for all cancers combined, the risk of death decreased by 20% between 2000-2002 and 2006-2008. The figures are consistent with various international estimates and are the result of progress in treatment regimens and collaborative clinical trials. The challenge for the French registries is now to study the long-term follow-up of survivors to estimate the incidence of long-term morbidities and adverse effects of treatments

Population-mixing at the place of residence at the time of birth and incidence of childhood leukaemia in France.

The association between the risk of childhood leukaemia before age 7 years and population-mixing at the place of residence at birth was investigated by retrospectively considering all the children born in mainland French communes between 1st January 1990 and 31st December 1998. An increased risk of acute lymphoblastic leukaemia was found with higher levels of migration for children residing at birth in isolated communes with a population density > or =50 people per km2 (SIRR = 2.59, 95% CI: 1.48-4.49). No association was observed with lower population densities. For children residing in non-isolated communes at birth, the results were similar but less marked. The risk tended to increase only for population densities > or =5000 people per km2 (SIRR = 1.57, 95% CI: 0.99-2.52). The findings are consistent with epidemic models and support the hypothesis of an infectious aetiology relating to population-mixing. Population density may be seen as an indicator of the opportunity of contacts between inhabitants and should therefore be taken into account when investigating an infectious hypothesis. This is the first systematic study of population-mixing at the place of residence at the time of birth to be conducted on a national scale

Childhood cancer survival in France, 1990-1999.

ERMAInternational audienceThe aim of this study was to describe the overall survival after childhood cancer in France using follow-up data from regional population-based registries. The survival of children (aged under 15 years) diagnosed with a cancer during 1990-1999 was analysed. For all cancers, the survivals were, respectively, 90.3% [89.4-91.3] at 1-year, 75.2% [73.8-76.6] at 5 years and 72.2% [70.7-73.7] at 10 years. During the 1990s, the average improvement in the 5-year survival was +1.2% per year. Adjusted for gender, age, area of residence and stage, children with cancer diagnosed between 1995 and 1999 had a 0.80 reduced risk of dying compared with those whose cancer had been diagnosed between 1990 and 1994. The increase of survival at the population level reflects a global improvement in childhood cancer care. The Paediatric Registries, in association with the French Society of Childhood Cancer, are now collecting data to quantify on a national basis the other events, at least relapse and second cancers