Conditional copula models for correlated survival endpoints: Individual patient data meta-analysis of randomized controlled trials.

Correlations among survival endpoints are important for exploring surrogate endpoints of the true endpoint. With a valid surrogate endpoint tightly correlated with the true endpoint, the efficacy of a new drug/treatment can be measurable on it. However, the existing methods for measuring correlation between two endpoints impose an invalid assumption: correlation structure is constant across different treatment arms. In this article, we reconsider the definition of Kendall's concordance measure (tau) in the context of individual patient data meta-analyses of randomized controlled trials. According to our new definition of Kendall's tau, its value depends on the treatment arms. We then suggest extending the existing copula (and frailty) models so that their Kendall's tau can vary across treatment arms. Our newly proposed model, a joint frailty-conditional copula model, is the implementation of the new definition of Kendall's tau in meta-analyses. In order to facilitate our approach, we develop an original R function condCox.reg(.) and make it available in the R package joint.Cox (https://CRAN.R-project.org/package=joint.Cox). We apply the proposed method to a gastric cancer dataset (3288 patients in 14 randomized trials from the GASTRIC group). This data analysis concludes that Kendall's tau has different values between the surgical treatment arm and the adjuvant chemotherapy arm (p-value<0.001), whereas disease-free survival remains a valid surrogate at individual level for overall survival in these trials.

Long-term outcomes of early initiated antiretroviral therapy in sub-Saharan children: a Cameroonian cohort study (ANRS-12140 Pediacam study, 2008-2013, Cameroon).

BACKGROUND: In most studies, the virological response is assessed during the first two years of antiretroviral treatment initiated in HIV-infected infants. However, early initiation of antiretroviral therapy exposes infants to very long-lasting treatment. Moreover, maintaining viral suppression in children is difficult. We aimed to assess the virologic response and mortality in HIV-infected children after five years of early initiated antiretroviral treatment (ART) and identify factors associated with virologic success in Cameroon. METHODS: In the ANRS-12140 Pediacam cohort study, 2008-2013, Cameroon, we included all the 149 children who were still alive after two years of early ART. Virologic response was assessed after 5 years of treatment. The probability of maintaining virologic success between two and five years of ART was estimated using Kaplan-Meier curve. The immune status and mortality were also studied at five years after ART initiation. Factors associated with a viral load < 400 copies/mL in children still alive at five years of ART were studied using logistic regressions. RESULTS: The viral load after five years of early ART was suppressed in 66.8% (60.1-73.5) of the 144 children still alive and in care. Among the children with viral suppression after two years of ART, the probability of maintaining viral suppression after five years of ART was 64.0% (54.0-74.0). The only factor associated with viral suppression after five years of ART was achievement of confirmed virological success within the first two years of ART (OR = 2.7 (1.1-6.8); p = 0.033). CONCLUSIONS: The probability of maintaining viral suppression between two and five years of early initiated ART which was quite low highlights the difficulty of parents to administer drugs daily to their children in sub-Saharan Africa. It also stressed the importance of initial viral suppression for achieving and maintaining virologic success in the long-term. Further studies should focus on identifying strategies that would enhance better retention in care and improved adherence to treatment within the first two years of ART early initiated in Sub-Saharan HIV-infected children.

How to use frailtypack for validating failure-time surrogate endpoints using individual patient data from meta-analyses of randomized controlled trials.

BACKGROUND AND OBJECTIVE: The use of valid surrogate endpoints can accelerate the development of phase III trials. Numerous validation methods have been proposed with the most popular used in a context of meta-analyses, based on a two-step analysis strategy. For two failure time endpoints, two association measures are usually considered, Kendall's τ at individual level and adjusted R2 ([Formula: see text]) at trial level. However, [Formula: see text] is not always available mainly due to model estimation constraints. More recently, we proposed a one-step validation method based on a joint frailty model, with the aim of reducing estimation issues and estimation bias on the surrogacy evaluation criteria. The model was quite robust with satisfactory results obtained in simulation studies. This study seeks to popularize this new surrogate endpoints validation approach by making the method available in a user-friendly R package. METHODS: We provide numerous tools in the frailtypack R package, including more flexible functions, for the validation of candidate surrogate endpoints using data from multiple randomized clinical trials. RESULTS: We implemented the surrogate threshold effect which is used in combination with [Formula: see text] to make decisions concerning the validity of the surrogate endpoints. It is also possible thanks to frailtypack to predict the treatment effect on the true endpoint in a new trial using the treatment effect observed on the surrogate endpoint. The leave-one-out cross-validation is available for assessing the accuracy of the prediction using the joint surrogate model. Other tools include data generation, simulation study and graphic representations. We illustrate the use of the new functions with both real data and simulated data. CONCLUSION: This article proposes new attractive and well developed tools for validating failure time surrogate endpoints.

Early treated HIV-infected children remain at risk of growth retardation during the first five years of life: Results from the ANRS-PEDIACAM cohort in Cameroon.

BACKGROUND: Long-term growth in HIV-infected infants treated early in resource-limited settings is poorly documented. Incidence of growth retardation, instantaneous risk of death related to malnutrition and growth parameters evolution during the first five years of life of uninfected and early treated HIV-infected children were compared and associated factors with growth retardation were identified. METHODS: Weight-for-age (WAZ), weight-for-length (WLZ), and length-for-age (LAZ) Z-scores were calculated. The ANRS-PEDIACAM cohort includes four groups of infants with three enrolled during the first week of life: HIV-infected (HI, n = 69), HIV-exposed uninfected (HEU, n = 205) and HIV-unexposed uninfected (HUU, n = 196). The last group included HIV-infected infants diagnosed before 7 months of age (HIL, n = 141). The multi-state Markov model was used to describe the incidence of growth retardation and identified associated factors. RESULTS: During the first 5 years, 27.5% of children experienced underweight (WAZ<-2), 60.4% stunting (LAZ<-2) and 41.1% wasting (WLZ<-2) at least once. The instantaneous risk of death observed from underweight state (35.3 [14.1-88.2], 84.0 [25.5-276.3], and 6.0 [1.5-24.1] per 1000 person-months for 0-6 months, 6-12 months, and 12-60 months respectively) was higher than from non-underweight state (9.6 [5.7-16.1], 20.1 [10.3-39.4] and 0.3 [0.1-0.9] per 1000 person-months). Compared to HEU, HIL and HI children were most at risk of wasting (adjusted HR (aHR) = 4.3 (95%CI: 1.9-9.8), P<0.001 and aHR = 3.3 (95%CI: 1.4-7.9), P = 0.01 respectively) and stunting for HIL (aHR = 8.4 (95%CI: 2.4-29.7). The risk of underweight was higher in HEU compared to HUU children (aHR = 5.0 (CI: 1.4-10.0), P = 0.001). Others associated factors to growth retardation were chronic pathologies, small size at birth, diarrhea and CD4< 25%. CONCLUSIONS: HIV-infected children remained at high risk of wasting and stunting within the first 5 years period of follow-up. There is a need of identifying suitable nutritional support and best ways to integrate it with cART in pediatric HIV infection global care.

One-step validation method for surrogate endpoints using data from multiple randomized cancer clinical trials with failure-time endpoints.

A surrogate endpoint can be used instead of the most relevant clinical endpoint to assess the efficiency of a new treatment. Before being used, a surrogate endpoint must be validated based on appropriate methods. Numerous validation approaches have been proposed with the most popular used in a context of meta-analysis, based on a two-step analysis strategy. For two failure-time endpoints, two association measurements are usually used, Kendall's τ at the individual level and the adjusted coefficient of determination ( Rtrial,adj2 ) at the trial level. However, Rtrial,adj2 is not always available due to model estimation constraints. We propose a one-step validation approach based on a joint frailty model, including both individual-level and trial-level random effects. Parameters have been estimated using a semiparametric penalized marginal log-likelihood method, and various numerical integration approaches were considered. Both individual- and trial-level surrogacy were evaluated using a new definition of Kendall's τ and the coefficient of determination. Estimators' performances were evaluated using simulation studies and satisfactory results were found. The model was applied to individual patient data meta-analyses in gastric cancer to assess disease-free survival as a surrogate for overall survival, as part of the evaluation of adjuvant therapy.

Low rate of early vertical transmission of HIV supports the feasibility of effective implementation of the national PMTCT guidelines in routine practice of referral hospitals in Cameroon.

Background: Vertical (VT) transmission of HIV remains a public health concern in sub-Saharan Africa. Objective: To investigate the VT rate and factors associated with transmission in routine practice in three referral hospitals in Cameroon. Methods: All HIV-infected mothers who delivered in maternity wards or sought paediatric services during the first postnatal week from November 2007 to October 2010 were invited to participate in the ANRS-Pediacam cohort. Their infants were followed at 6, 10 and 14 weeks of life and HIV status was determined from the 6th week of life using real-time PCR. For those who were breastfed and negative at the first PCR, a second test was performed 6 weeks after breast-feeding was stopped. Logistic regression was performed to identify the independent risk factors of VT. Results: Overall, 2053 HIV-exposed infants were enrolled. Of these, 1827 were tested for HIV including 1777 before the age of 3 months, and 59 were HIV-infected, resulting in an overall early VT rate of 3.3% (CI 2.5-4.3). The VT rate was significantly associated with the type of maternal exposure to ART (0.5%, 2/439, p<0.001, CI 0.0-1.6) in mothers who commenced HAART before pregnancy, 1.9% (6/321, CI 0.7-4.0) in mothers who commenced HAART during pregnancy, 4.1% (34/837, CI 2.8-5.6) in those on short-course ART and 11.1% (17/153, CI 6.6-17.2) in mothers not receiving ART. On multivariate analysis, the type of exposure to ART remained significantly associated with being small for gestational age (aOR 5.0, CI 2.4-10.3, p < 0.001) and female gender (aOR 2.1, CI 1.2-3.8, p = 0.01). Conclusion: The successfully low rate of VT transmission of HIV in mothers who commenced HAART in early pregnancy strongly supports the need to improve access to diagnosis and early treatment of all women of childbearing age with HIV through the national PMTCT programme. Abbreviations: ANRS: French National Agency for Research on AIDS and Viral Hepatitis; ART: antiretroviral therapy; ARV: antiretroviral; AUDIPOG: Association des Utilisateurs de Dossiers Informatisés en Pédiatrie, Obstétrique et Gynécologie; CHM/MCC-CBF: The Central Hospital Maternity/Mother and Child Centre of the Chantal Biya Foundation; EHC: Essos Hospital Centre; EPI: Expanded Programme on Immunization; HAART: highly active antiretroviral therapy; HBV: hepatitis B virus; IQR: interquartile range; LH: Laquintinie Hospital; MTCT: mother-to-child transmission; NVP: nevirapine; Pediacam: Pediatrie Cameroun; PMTCT: prevention of mother-to-child transmission; SGAG: small for gestational age and gender; UNAIDS: Joint United Nations Program on HIV/AIDS; WHO: World Health Organization; ZDV: zidovudine; 3TC: lamivudine.

Improving systematic rabies surveillance in Cameroon: A pilot initiative and results for 2014-2016.

Canine rabies is endemic in Cameroon, but human rabies exposures and cases are likely underreported because of inadequate surveillance. In 2014, the surveillance network in the West region of Cameroon was reinforced by introducing a new anti-rabies center, a framework for data collection and evaluation, provisions for sample collecting and laboratory confirmation, and training for health professionals. The objective of this observational cohort study was to describe the incidence and characteristics of reported exposures and human and animal rabies cases following this reinforcement of the existing rabies surveillance system. The surveillance network consisted of local, regional, and national health and veterinary authorities in 11 of the 20 West region districts, and was completely integrated within the existing national rabies surveillance network. Animal exposures and suspected rabies exposures, the suspected rabid animals involved, and laboratory confirmation of human and animal rabies cases were recorded in a centralized information database. Between January 2014 and June 2016, the network recorded 1340 animal exposure cases for an overall incidence rate of 38.2 animal exposures per 100,000 people, four confirmed rabies-positive animals, and one confirmed human rabies case out of four clinically suspected cases. In contrast, 62 animal exposures and an overall incidence rate of 6.1 exposures per 100,000 people were reported for the West region districts not participating in the reinforced surveillance. Of the 925 animal exposure victims for whom a detailed case report form was completed, 703 were considered to be at risk of rabies and only 428 (61%) of these received any post-exposure prophylaxis in the form of rabies vaccine. Obstacles encountered within the network included low rates of animal sample submission and animal follow-up by veterinarians. Reinforced rabies surveillance in the West region of Cameroon has provided the most accurate estimate of the region's disease and exposure burdens to date, and indicates that animal exposures are substantially underreported. The reinforced network also signaled that greater access to post-exposure prophylaxis is needed. Integration of regions not covered by the surveillance network and efforts to improve engagement of veterinary services will be needed to reveal the true burden of rabies in Cameroon.

Virologic Response to Early Antiretroviral Therapy in HIV-infected Infants: Evaluation After 2 Years of Treatment in the Pediacam Study, Cameroon.

INTRODUCTION: Little is known about virologic responses to early antiretroviral therapy (ART) in HIV-infected infants in resource-limited settings. We estimated the probability of achieving viral suppression within 2 years of ART initiation and investigated the factors associated with success. METHODS: We analyzed all 190 infants from the Cameroon Pediacam who initiated ART by 12 months of age. The main outcome measure was viral suppression (<1000 copies/mL) on at least 1 occasion; the other outcome measures considered were viral suppression (<400 copies/mL) on at least 1 occasion and confirmed viral suppression (both thresholds) on 2 consecutive occasions. We used competing-risks regression for a time-to-event analysis to estimate the cumulative incidence of outcomes and univariate and multivariate models to identify risk factors. RESULTS: During the first 24 months of ART, 20.0% (38) of the infants died, giving a mortality rate of 11.9 deaths per 100 infant-years (95% confidence interval: 8.1-15.7). The probability of achieving a viral load below 1000 or 400 copies/mL was 80.0% (69.0-81.0) and 78.0% (66.0-79.0), respectively. The probability of virologic suppression (with these 2 thresholds) on 2 consecutive occasions was 67.0% (56.0-70.0) and 60.0% (49.0-64.0), respectively. Virologic success was associated with not having missed any doses of treatment before the visit, but not with socioeconomic and living conditions. CONCLUSION: Many early treated children failed to achieve virologic suppression, likely due to a combination of adherence difficulties, drug dosing and viral resistance, which highlights the need for routine viral load monitoring. The high infant mortality despite early ART initiation needs to be addressed in sub-Saharan countries.

Cytomegalovirus infection in HIV-infected versus non-infected infants and HIV disease progression in Cytomegalovirus infected versus non infected infants early treated with cART in the ANRS 12140-Pediacam study in Cameroon.

BACKGROUND: The outcome of CMV/HIV co-infection in infants treated early with combined antiretroviral therapy (cART) in resource-limited settings has not been described. We aimed to estimate the prevalence and identify factors associated with early CMV infection in HIV-infected and non-infected infants included in a study in Cameroon, and to compare HIV disease progression and survival after 1 year of early cART, following infants' CMV status. METHODS: HIV-infected infants followed from birth or from HIV diagnosis before 7 months old and HIV-uninfected infants born to HIV-infected or uninfected mothers were tested for CMV at a median age of 4.0 months [Interquartile range (IQR): 3.4-4.9]. Multivariable logistic regression was performed to identify factors associated with CMV infection. Early cART was offered to HIV-infected infants: mortality, immunological and virological outcomes were assessed. RESULTS: Three hundred and sixty-nine infants were tested. The proportion of infants infected with CMV at baseline was significantly higher in HIV-infected than in HIV-uninfected groups (58.9% (86/146) vs 30.0% (67/223), p < 0.001). At baseline, median CMV viral load was higher in HIV-infected (3.7 log copies/ml [IQR; 3.1-4.3]) than in HIV-uninfected infants (2.8 log copies [IQR; 2.1-3.4], p < 0.001). cART was initiated in 90% of HIV-infected infants (132/146) at a median age of 4.0 months (IQR; 3.2-5.9); in this sub-group CMV infection was independently associated with being followed from the time of HIV diagnosis rather than from birth (aOR = 3.1, 95%CI [1.2-8.0]), born to a non-single mother (aOR = 3.4[1.4-8.1]), and breastfeeding (aOR = 7.3 [2.7-19.4]). HIV-infected infants were retested after a median of 7.1 months [4.8-9.5]: CMV was undetectable in 37 of the 61 (60.7%) initially CMV-infected cases and became detectable in 8 of the 38 (21.1%) initially CMV-negative cases. After 1 year of cART, the probability of death (0.185 vs 0.203; p = 0.75), the proportion of cases with HIV RNA viral load <400 copies/ml (75.5% vs 61.5%; p = 0.17) and the mean CD4 percentage increase (10.97% vs 6.88%; p = 0.15) did not differ between CMV+ and CMV- infants. CONCLUSIONS: We observed a high prevalence of CMV infection among HIV-infected infants. Early initiation of cART may have limited the negative impact of CMV even in the absence of specific anti-CMV treatment.

Could caregiver reporting adherence help detect virological failure in Cameroonian early treated HIV-infected infants?

BACKGROUND: Viral load is still the marker of choice for monitoring adherence to combined antiretroviral therapy (cART) and confirming the success of HIV treatment. Unfortunately it is difficult to access in many resource-poor settings. We aimed to measure the performance of caregiver reporting adherence for detecting virological failure in routine practice during the first 2 years after cART initiation in infants. METHODS: PEDIACAM is an ongoing prospective cohort study including HIV1-infected infants diagnosed before 7 months of age between November 2007 and October 2011 in Cameroon. Adherence was assessed using a questionnaire administered every 3 months from cART initiation; the HIV-RNA viral load was determined at the same visits. Virological failure was defined as having a viral load ≥ 1000 cp/mL at 3 and 12 months after cART initiation or having a viral load ≥ 400 cp/mL at 24 months after cART initiation. The performance of each current missed and cumulative missed dose defined according to adherence as reported by caregiver was assessed using the viral load as the gold standard. RESULTS: cART was initiated at a median age of 4 months (IQR: 3-6) in the 167 infants included. The cumulative missed dose showed the best overall performance for detecting virological failure after 12 months of cART (AUC test, p = 0.005, LR + =4.4 and LR- = 0.4). Whatever the adherence reporting criterion, the negative predictive value was high (NPV ≥ 75%) 12 and 24 months after cART initiation, whereas the positive predictive value was low (PPV ≤ 50%). CONCLUSIONS: The adherence questionnaire administered by the health care provider to the infants' caregivers is not reliable for detecting virological failure in routine practice: its positive predictive value is low. However, the cumulative missed dose measurement may be a reliable predictor of virological success, particularly after 12 months of cART, given its high negative predictive value.

Low birth weight in perinatally HIV-exposed uninfected infants: observations in urban settings in Cameroon.

BACKGROUND: The consequences of maternal HIV infection for fetal growth are controversial. Here, we estimated the frequency of small for gestational age and gender (SGAG) among neonates born to HIV-infected or uninfected mothers and assessed the contribution, if any, of maternal HIV to the risk of SGAG. METHODS: The data used were obtained from the ANRS-Pediacam cohort in Cameroon. Pairs of newborns, one to a HIV-infected mother and the other to an uninfected mother, were identified during the first week of life, and matched on gender and recruitment site from 2007-2010. SGAG was defined in line with international recommendations as a birth weight Z-score adjusted for gestational age at delivery and gender more than two standard deviations below the mean (-2SD). Considering the matched design, logistic regression modeling was adjusted on site and gender to explore the effect of perinatal HIV exposure on SGAG. RESULTS: Among the 4104 mother-infant pairs originally enrolled, no data on birth weight and/or gestational age were available for 108; also, 259 were twins and were excluded. Of the remaining 3737 mother-infant pairs, the frequency of SGAG was 5.3% (95%CI: 4.6-6.0), and was significantly higher among HIV-infected infants (22.4% vs. 6.3%; p<.001) and lower among HIV-unexposed uninfected infants (3.5% vs. 6.3%; p<.001) than among HIV-exposed uninfected infants. Similarly, SGAG was significantly more frequent among HIV-infected infants (aOR: 4.1; 2.0-8.1) and less frequent among HIV-unexposed uninfected infants (aOR: 0.5; 0.4-0.8) than among HIV-exposed uninfected infants. Primiparity (aOR: 1.9; 1.3-2.7) and the presence of any disease during pregnancy (aOR: 1.4; 1.0-2.0) were identified as other contributors to SGAG. CONCLUSION: Maternal HIV infection was independently associated with SGAG for HIV-exposed uninfected infants. This provides further evidence of the need for adapted monitoring of pregnancy in HIV-infected women, especially if they are symptomatic, to minimize additional risk factors for SGAG.