Using unconditional analysis in a case-sibling control design increases power to detect gene-environment (G x E) interaction

AbstractInternational audienc

Increased power to detect gene-environment interaction using siblings controls.: GxE interaction and siblings controls

International audiencePURPOSE: Interest is increasing in studying gene-environment (G x E) interaction in disease etiology. Study designs using related controls as a more appropriate control group for evaluating G x E interactions have been proposed but often assume unrealistic numbers of available relative controls. To evaluate a more realistic design, we studied the relative efficiency of a 1:0.5 case-sibling-control design compared with a classical 1:1 case-unrelated-control design and examined the effect of the analysis strategy. METHODS: Simulations were performed to assess the efficiency of a 1:0.5 case-sibling-control design relative to a classical 1:1 case-unrelated-control design under a variety of assumptions for estimating G x E interaction. Both matched and unmatched analysis strategies were examined. RESULTS: When using a matched analysis, the 1:1 case-unrelated-control design was almost always more powerful than the 1:0.5 case-sibling-control design. In contrast, when using an unmatched analysis, the 1:0.5 case-sibling-control design was almost always more powerful than the 1:1 case-unrelated-control design. The unconditional analysis of the case-sibling-control design to estimate G x E interaction, however, requires no correlation in E between siblings. CONCLUSIONS: In most settings, a matched analysis may be required and a 1:1 case-unrelated-control design will be more powerful than a 1:0.5 case-sibling-control design

Unconditional analyses can increase efficiency in assessing gene-environment interaction of the case-combined-control design.

BACKGROUND: A design combining both related and unrelated controls, named the case-combined-control design, was recently proposed to increase the power for detecting gene-environment (GxE) interaction. Under a conditional analytic approach, the case-combined-control design appeared to be more efficient and feasible than a classical case-control study for detecting interaction involving rare events. METHODS: We now propose an unconditional analytic strategy to further increase the power for detecting gene-environment (GxE) interactions. This strategy allows the estimation of GxE interaction and exposure (E) main effects under certain assumptions (e.g. no correlation in E between siblings and the same exposure frequency in both control groups). Only the genetic (G) main effect cannot be estimated because it is biased. RESULTS: Using simulations, we show that unconditional logistic regression analysis is often more efficient than conditional analysis for detecting GxE interaction, particularly for a rare gene and strong effects. The unconditional analysis is also at least as efficient as the conditional analysis when the gene is common and the main and joint effects of E and G are small. CONCLUSIONS: Under the required assumptions, the unconditional analysis retains more information than does the conditional analysis for which only discordant case-control pairs are informative leading to more precise estimates of the odds ratios

Cancer mortality during the 1968-1994 period in a mining area in France.

International audienceWe performed a geographical analysis of cancer mortality in the communes surrounding an industrial mining complex (Salsigne, France) where suspicious levels of pollution due to arsenic were measured. Compared with that observed in a control area, we showed a significant excess of mortality due to all cancer types (ratio of standard mortality ratios (ratio of SMRs)=1.1), lung cancer (ratio of SMRs=1.8), pharynx cancer (ratio of SMRs=2.1) in the whole population, and due to digestive system cancer (ratio of SMRs=1.3) among women. The results were similar after controlling for the occupation distribution in the populations. Excluding mining complex workers deaths from the deaths in the studied populations did not modify the pattern of our results. We concluded that the excess of cancer deaths could not be exclusively due to potential professional exposures among the workers of the mining complex and are probably explained by environmental contamination

Cancer mortality during the 1968-1994 period in a mining area in France.

International audienceWe performed a geographical analysis of cancer mortality in the communes surrounding an industrial mining complex (Salsigne, France) where suspicious levels of pollution due to arsenic were measured. Compared with that observed in a control area, we showed a significant excess of mortality due to all cancer types (ratio of standard mortality ratios (ratio of SMRs)=1.1), lung cancer (ratio of SMRs=1.8), pharynx cancer (ratio of SMRs=2.1) in the whole population, and due to digestive system cancer (ratio of SMRs=1.3) among women. The results were similar after controlling for the occupation distribution in the populations. Excluding mining complex workers deaths from the deaths in the studied populations did not modify the pattern of our results. We concluded that the excess of cancer deaths could not be exclusively due to potential professional exposures among the workers of the mining complex and are probably explained by environmental contamination

[Could treatments with beta-blockers be associated with a reduction in cancer risk?]

BACKGROUND: The relationship between the use of anti-hypertensive drugs and cancer risk remains controversial. The main objective of this study was to assess the potential effect of beta-blocker use on cancer risk. METHODS: In a cohort of 839 patients with cardiovascular disease, followed up prospectively for an average period of 10 years, cancer occurrence was recorded according to the exposure to beta-blockers. The relative risk of cancer associated with beta-blocker use was estimated using a Cox model adjusted on gender and age. Ever- vs never-use of beta-blockers and duration of exposure to the drug were analyzed as time-dependent variables. In addition, the standardized incidence ratios (SIR) were calculated using the corresponding age- and gender-adjusted cancer incidences in the French general population. RESULTS: A total of 326 beta-blocker users and 513 users of other treatments were included in the cohort. During the follow-up period, representing 8,466 person-years, incident cancer cases were 15 and 59 in beta-blocker ever-users versus never-users, respectively. Using the Cox model, the overall relative risk of cancer was 0.51 (95% confidence interval [95% CI]: 0.29-0.90) in the beta-blocker ever-users versus never-users (p=0.02), with a 6% decrease per year of use (95% CI: 1%-12%; p=0.03). The corresponding SIR ratio between these two groups was 0.44 (95% CI: 0.24-0.76). CONCLUSION: In this cohort, the beta-blocker treatments appeared to decrease the cancer risk significantly. However, this result should be considered with caution; further work is needed, as some sources of bias associated with this type of epidemiological study cannot be totally excluded

[Could treatments with beta-blockers be associated with a reduction in cancer risk?]

BACKGROUND: The relationship between the use of anti-hypertensive drugs and cancer risk remains controversial. The main objective of this study was to assess the potential effect of beta-blocker use on cancer risk. METHODS: In a cohort of 839 patients with cardiovascular disease, followed up prospectively for an average period of 10 years, cancer occurrence was recorded according to the exposure to beta-blockers. The relative risk of cancer associated with beta-blocker use was estimated using a Cox model adjusted on gender and age. Ever- vs never-use of beta-blockers and duration of exposure to the drug were analyzed as time-dependent variables. In addition, the standardized incidence ratios (SIR) were calculated using the corresponding age- and gender-adjusted cancer incidences in the French general population. RESULTS: A total of 326 beta-blocker users and 513 users of other treatments were included in the cohort. During the follow-up period, representing 8,466 person-years, incident cancer cases were 15 and 59 in beta-blocker ever-users versus never-users, respectively. Using the Cox model, the overall relative risk of cancer was 0.51 (95% confidence interval [95% CI]: 0.29-0.90) in the beta-blocker ever-users versus never-users (p=0.02), with a 6% decrease per year of use (95% CI: 1%-12%; p=0.03). The corresponding SIR ratio between these two groups was 0.44 (95% CI: 0.24-0.76). CONCLUSION: In this cohort, the beta-blocker treatments appeared to decrease the cancer risk significantly. However, this result should be considered with caution; further work is needed, as some sources of bias associated with this type of epidemiological study cannot be totally excluded

Causalité du gène ATM dans le développement d'un cancer du sein : tendance ou pas tendance ?

AbstractNational audienceObjectifs : L'Ataxie télangiectasie (AT) est une maladie récessive de l'enfant caractérisée par une ataxie cérébelleuse dégénérative, des télangiectasies cutanées ou muqueuses, un déficit immunitaire et un risque augmenté de cancer. Des études sur les apparentés de patients AT ont montré que les femmes hétérozygotes AT (HetAT) ont un risque de cancer du sein (CS) multiplié par ~3 par rapport à la population générale. Cependant, la causalité des gènes de l'AT dans le CS est discutée : peu d'études en population générale (c'est-à-dire cas de CS non sélectionnés) de type cas témoin ou de cohorte ont observé une association entre le gène ATM et le CS (ex : FitzGerald et al., 1997) et aucune étude sur les apparentés de patients AT n'observe de tendance entre l'augmentation de la probabilité d'être porteur d'une mutation des gènes de l'AT et le risque de CS (J. Hall, 2005). Dans ce travail, nous nous sommes particulièrement intéressés à l'absence de tendance en explorant l'hypothèse qu'elle pouvait être partiellement expliquée par le mode de recensement des apparentés et par les méthodes utilisées pour déterminer leur statut vis-à-vis de la mutation ATM (statut ATM), méthodes pouvant a posteriori s'avérer plus ou moins biaisées. Données et méthodes : De 1994 à 1997, 34 familles ont été recensées à partir d'enfants AT. Les données démographiques, la survenue de cancer et les prélèvements sanguins ont été recueillis auprès des apparentés du 1er au 3e degré de l'enfant AT (Janin et al., 1999). Le nombre observé de cancers a été comparé au nombre attendu calculé à partir des données d'incidence estimées France entière. Trois méthodes ont été utilisées pour définir le statut ATM des individus : (1) l'approche « a priori » : le statut est déterminé par la probabilité d'être porteur de la mutation selon le degré de parenté avec l'enfant AT ; (2) l'approche « mixte » : le statut est déterminé par l'étude moléculaire ou en l'absence de prélèvement sanguin, calculé à partir du statut de l'apparenté testé le plus proche ; (3) l'approche « mixte corrigée » : afin d'éviter le biais potentiel dû au fait que seuls les survivants ont pu être testés, le statut d'un individu testé est déterminé par la probabilité a priori d'être porteur, le résultat de l'étude moléculaire servant alors à déterminer le statut de ses apparentés (Olsen et al., 2005). Résultats : Quelle que soit la méthode utilisée, on observe un risque relatif (RR) de CS élevé chez les HetAT. Ce RR est moins élevé mais plus précis avec l'approche « mixte » (RR = 3,88) qu'avec l'approche « a priori » (RR = 4,48) ou l'approche « mixte corrigée » (RR = 5,13). Le RR de CS est particulièrement élevé dans le groupe des mères (RR = 7,1), mais aussi dans le groupe des apparentées ayant une probabilité 0,125 d'être porteuse. Chez ces dernières, l'excès de risque semble être dû à un sur-échantillonnage de fratries éloignées lorsqu'un des membres de cette fratrie a un antécédent de cancer. En ignorant cette catégorie, le test de tendance est significatif avec les approches « a priori » (p = 0,012) et « mixte corrigée » (p = 0,048). Conclusion : Les méthodes utilisées pour déterminer le statut ATM modifient peu les estimations du RR de CS chez les HetAT. Par contre, la précision des estimations y est très sensible. La prise en compte des données moléculaires a clairement introduit un biais dû au sur-génotypage des cas de CS comparé aux apparentés non atteints. Ce biais se traduit par une sous estimation du risque de CS chez les apparentés au génotype incertain, expliquant l'absence de tendance initialement observée. Le test de tendance significatif observé en utilisant les méthodes « a priori » et « mixte corrigée » va dans le sens d'un lien de causalité entre ATM et CS. Le risque paraît plus élevé chez les mères que chez les autres HetAT mais les faibles effectifs ne permettent pas la mise en évidence d'une différence significative entre ces deux groupes. Des études à un échelon international permettront de préciser l'association entre ATM et CS

Possible relationship between the van der Woude syndrome (vWS) locus and nonsyndromic cleft lip with or without cleft palate (NSCL/P).

Cleft lip with or without cleft palate (CL/P) is one of the most common congenital malformations in humans occurring with a birth prevalence of approximately 1:1,000. CL/P may be part of a defined syndrome, sequence or association, although most individual or familial cases present as an isolated (nonsyndromic) malformation (NSCL/P). Inheritance is generally regarded as multigenic although, in some families, NSCL/P seemingly segregates as a monogenic trait. On the other hand, van der Woude syndrome (vWS) is a rare autosomal dominant with cardinal features of lower-lip pits (LLP) and CL/P or cleft palate (alone). Since none of these traits is present in all mutation carriers, some individual or familial vWS cases, especially those lacking LLP, are indiscernible from NSCL/P, raising the question whether allelic variation at the vWS locus could underlie NSCL/P. This question was addressed using parametric linkage (LOD score) analysis in 21 multiplex NSCL/P families based on a tightly linked microsatellite marker (D1S3753), and nonparametric analysis using the transmission/disequilibrium test (GTDT) in 106 NSCL/P triads and selecting markers D1S205, D1S491, and D1S3753. No evidence for linkage of NSCL/P to vWS was found on the 21 families using the LOD score approach. In contrast, TDT yielded a significant P value of 0.04 for D1S205, supporting involvement of vWS in NSCL/P in a complex, modifying/polygenic manner rather than as a monogenic/major disease locus