A new cure model that corrects for increased risk of non-cancer death: analysis of reliability and robustness, and application to real-life data.

BACKGROUND: Non-cancer mortality in cancer patients may be higher than overall mortality in the general population due to a combination of factors, such as long-term adverse effects of treatments, and genetic, environmental or lifestyle-related factors. If so, conventional indicators may underestimate net survival and cure fraction. Our aim was to propose and evaluate a mixture cure survival model that takes into account the increased risk of non-cancer death for cancer patients. METHODS: We assessed the performance of a corrected mixture cure survival model derived from a conventional mixture cure model to estimate the cure fraction, the survival of uncured patients, and the increased risk of non-cancer death in two settings of net survival estimation, grouped life-table data and individual patients' data. We measured the model's performance in terms of bias, standard deviation of the estimates and coverage rate, using an extensive simulation study. This study included reliability assessments through violation of some of the model's assumptions. We also applied the models to colon cancer data from the FRANCIM network. RESULTS: When the assumptions were satisfied, the corrected cure model provided unbiased estimates of parameters expressing the increased risk of non-cancer death, the cure fraction, and net survival in uncured patients. No major difference was found when the model was applied to individual or grouped data. The absolute bias was < 1% for all parameters, while coverage ranged from 89 to 97%. When some of the assumptions were violated, parameter estimates appeared more robust when obtained from grouped than from individual data. As expected, the uncorrected cure model performed poorly and underestimated net survival and cure fractions in the simulation study. When applied to colon cancer real-life data, cure fractions estimated using the proposed model were higher than those in the conventional model, e.g. 5% higher in males at age 60 (57% vs. 52%). CONCLUSIONS: The present analysis supports the use of the corrected mixture cure model, with the inclusion of increased risk of non-cancer death for cancer patients to provide better estimates of indicators based on cancer survival. These are important to public health decision-making; they improve patients' awareness and facilitate their return to normal life.

Carcinoembryonic antigen kinetics predict response to first-line treatment in metastatic colorectal cancer: Analysis from PRODIGE 9 trial.

BACKGROUND: To examine the relationship between carcinoembryonic antigen (CEA) kinetics and prognosis in metastatic colorectal cancer (mCRC) patients receiving first-line chemotherapy in the PRODIGE9 trial. METHODS: Associations between monthly CEA measurements within 6 months since baseline and progression-free survival (PFS) were evaluated using a joint-latent class-mixed model. A validation set was used to test our prognosis model. Correlations between CEA trajectories (classes) and baseline characteristics were also investigated. RESULTS: Three classes were identified. Class 1 had low baseline CEA with small variations. Class 2 had high baseline CEA with a rapid decrease reaching the same CEA level at 6 months as in class 1. Class 3 had high baseline CEA with a transient decrease followed by an increase to reach, at 6 months, the same CEA level as at baseline. Six-month PFS was significantly lower in class 3 than in classes 1 and 2 (57% vs. 91% and 93% respectively; p<0.01). Class 3 was significantly associated with ECOG 2 status, a high LDH level and non-resected primary tumor. DISCUSSION: Variations in CEA kinetics correlate with prognosis in patients receiving first-line chemotherapy for mCRC. We propose here a user-friendly application to classify CEA trajectory.

Impact of G-CSF Prophylaxis on Chemotherapy Dose-Intensity, Link Between Dose-Intensity and Survival in Patients with Metastatic Pancreatic Adenocarcinoma.

BACKGROUND: In metastatic pancreatic adenocarcinoma, few data are available on the use of granulocyte-colony stimulating factor (G-CSF) prophylaxis and its impact on dose-intensity (DI), or the link between DI and progression-free survival (PFS). This study assessed the impact of G-CSF prophylaxis on the DI received by patients and the relationship between full DI and PFS according to chemotherapy regimens. PATIENTS AND METHODS: Patients from three first-line randomized phase II clinical trials were included in this retrospective cohort. G-CSF prophylaxis groups were identified and balanced according to baseline characteristics using a propensity score. Patients were classified into 2 treatment groups (FOLFIRINOX vs FOLFIRI/nab-paclitaxel (NAB)). DI was a binary variable (full/reduced). Adverse events were defined using NCI-CTCAE v4.0. RESULTS: Of the 498 patients, 154 (31%) were in "prophylaxis" group; 179 (36%) were treated by FOLFIRINOX and 319 (64%) by FOLFIRI/NAB. In FOLFIRINOX group, G-CSF prophylaxis was significantly associated with a higher rate of full DI (OR, 5.07; 95% CI, 1.52-16.90; P < .01) while in FOLFIRI/NAB group, it was significantly associated with a lower rate of full DI (OR, 0.23; 95% CI, 0.06-0.83; P = .03). Full DI was associated with a non-significant increase in PFS (FOLFIRINOX group: HR 0.83; 95% CI, 0.59-1.16; P = .27; FOLFIRI/NAB group: HR 0.84; 95% CI, 0.63-1.11; P = .22). CONCLUSION: Granulocyte-colony stimulating factor prophylaxis was associated with a higher rate of full DI with FOLFIRINOX. Full DI was associated with a non-significant increase in PFS. These results need to be confirmed prospectively.

Neoadjuvant treatment for borderline resectable pancreatic adenocarcinoma is associated with higher R0 rate compared to upfront surgery.

BACKGROUND: Neoadjuvant treatment (NAT) is debated for borderline resectable pancreatic cancer (BRPC). This retrospective study assessed the impact of NAT on R0 rate and survival for BRPC patients in comparison with upfront surgery (US). MATERIAL AND METHODS: Between 2010 and 2017 patient records for all consecutive patients treated for BRPC according to NCCN 2017 were reviewed. The endpoints analysed were R0 rate, recurrence-free-survival (RFS) and overall survival (OS). RESULTS: Seventy-nine patients were included: 63 (79.7%) patients received NAT and 16 (20.3%) were upfront operated. NAT consisted in FOLFIRINOX (median cycles: 5, range 4-8) followed by chemoradiation (n = 55, 87.3%, median dose: 54 Gy). Thirty-nine (61.9%) patients had resection. R0 rate was higher in the NAT group considering a margin clearance of 0 mm (94.9%) or 1 mm (89.7%) compared to the US group (68.8% and 43.8% respectively). In the whole population, median RFS was 12.6 [95%CI: 10.5-22.1] in the NAT group vs 7.7 [95%CI: 4.4-14] months in the US group (p < 0.01). Median OS was 29.0 [95%CI: 23.5-63.1] and 27.2 [95%CI: 11.6-38.8] months in the NAT and US groups respectively (p = 0.06). In operated patients the NAT group achieved better RFS and OS than the US group (p < 0.01 for both). In multivariate analysis NAT, surgical resection and age <65 (p < 0.01 for both) were prognostic of RFS. NAT, surgical resection and adjuvant chemotherapy were prognostic of OS (p < 0.05 for all). In operated patients (n = 55) multivariate analysis showed that N1 status was associated with decreased RFS; age < 65 and NAT were associated with a longer RFS. Receiving a NAT, an adjuvant chemotherapy and achieving a ypT0-1N0 status were associated with better OS. NAT was well tolerated with 14.3% grade ≥ 3 toxicities. CONCLUSION: NAT permitted a high R0 rate with a 0- or 1-mm clearance margin and was associated with better RFS and OS for patients with BRPC.

Predictive factors of severe early treatment-related toxicity in patients receiving first-line treatment for metastatic colorectal cancer: Pooled analysis of 2190 patients enrolled in Fédération Francophone de Cancérologie Digestive (FFCD) trials.

AIM: Few studies have explored the association between baseline characteristics and the occurrence of early toxicities in patients treated with first-line chemotherapy for metastatic colorectal cancer (mCRC). PATIENTS AND METHODS: Individual patient data of 2190 patients enrolled in 10 prospective FFCD (Fédération Francophone de Cancérologie Digestive) trials were analysed. Severe early toxicity was defined as the occurrence of grade ≥III toxicity within 3 months after initiation of chemotherapy (ET3). RESULTS: Patients received monotherapy based on 5-FU (n = 1068), a cytotoxic doublet (n = 395) or tritherapy with a cytotoxic doublet plus anti-VEGF agent or a cytotoxic triplet (n = 727). The patients received 5-FU (100%), Irinotecan (39.6%), Oxaliplatin (13.4%), Bevacizumab (29.6%) or Aflibercept (1.8%). ET3 occurred in 244 patients (22.8%) with monotherapy, 248 patients (62.8%) with doublet and 392 patients (53.9%) with tritherapy. The most frequent ET3s were related to biological abnormalities and/or gastrointestinal, general and vascular disorders. The prognostic factors for the occurrence of an ET3 in multivariate analysis were a performance status of 2 rather than 0-1 (OR 2.57; 95% CI [1.16, 5.73]; p = 0.02), tritherapy versus monotherapy (OR 2.31; 95% CI [0.84, 6.33]; p = 0.02), alkaline phosphatase > 300 UI/l (OR 3.07; 95% CI [1.79, 5.27]; p < 0.001) and non-resected primary tumour versus resection (OR 1.59; 95% CI [1.06, 2.39]; p = 0.02). Median overall survival in patients without ET3 was significantly longer than that in patients with ET3 (HR 0.87; 95% CI [0.80-0.96]; p = 0.004). CONCLUSION: ET3 is frequent whatever the treatment regimen and is associated with certain baseline characteristics. The clinical impact of ET3 on prognosis in mCRC warrants further investigation.

Flexible Modeling of Net Survival and Cure by AML Subtype and Age: A French Population-Based Study from FRANCIM.

With improvements in acute myeloid leukemia (AML) diagnosis and treatment, more patients are surviving for longer periods. A French population of 9453 AML patients aged ≥15 years diagnosed from 1995 to 2015 was studied to quantify the proportion cured (P), time to cure (TTC) and median survival of patients who are not cured (MedS). Net survival (NS) was estimated using a flexible model adjusted for age and sex in sixteen AML subtypes. When cure assumption was acceptable, the flexible cure model was used to estimate P, TTC and MedS for the uncured patients. The 5-year NS varied from 68% to 9% in men and from 77% to 11% in women in acute promyelocytic leukemia (AML-APL) and in therapy-related AML (t-AML), respectively. Major age-differenced survival was observed for patients with a diagnosis of AML with recurrent cytogenetic abnormalities. A poorer survival in younger patients was found in t-AML and AML with minimal differentiation. An atypical survival profile was found for acute myelomonocytic leukemia and AML without maturation in both sexes and for AML not otherwise specified (only for men) according to age, with a better prognosis for middle-aged compared to younger patients. Sex disparity regarding survival was observed in younger patients with t-AML diagnosed at 25 years of age (+28% at 5 years in men compared to women) and in AML with minimal differentiation (+23% at 5 years in women compared to men). All AML subtypes included an age group for which the assumption of cure was acceptable, although P varied from 90% in younger women with AML-APL to 3% in older men with acute monoblastic and monocytic leukemia. Increased P was associated with shorter TTC. A sizeable proportion of AML patients do not achieve cure, and MedS for these did not exceed 23 months. We identify AML subsets where cure assumption is negative, thus pointing to priority areas for future research efforts.

Impact of time-varying cumulative bevacizumab exposures on survival: re-analysis of data from randomized clinical trial in patients with metastatic colo-rectal cancer.

BACKGROUND: As cancer treatment, biotherapies can be as effective as chemotherapy while reducing the risk of secondary effects, so that they can be taken over longer periods than conventional chemotherapy. Thus, some trials aimed at assessing the benefit of maintaining biotherapies during chemotherapy-free intervals (CFI). For example, the recent PRODIGE9 trial assessed the effect of maintaining bevacizumab during CFI in metastatic colorectal cancer (mCRC) patients. However, its analysis was hindered by a small difference of exposure to the treatment between the randomized groups and by a large proportion of early drop outs, leading to a potentially unbalanced distribution of confounding factors among the trial completers. To address these limitations, we re-analyzed the PRODIGE9 data to assess the effects of different exposure metrics on all-cause mortality of patients with mCRC using methods originally developed for observational studies. METHODS: To account for the actual patterns of drug use by individual patients and for possible cumulative effects, we used five alternative time-varying exposure metrics: (i) cumulative dose, (ii) quantiles of the cumulative dose, (iii) standardized cumulative dose, (iv) Theoretical Blood Concentration (TBC), and (v) Weighted Cumulative Exposure (WCE). The last two metrics account for the timing of drug use. Treatment effects were estimated using adjusted Hazard Ratio from multivariable Cox proportional hazards models. RESULTS: After excluding 112 patients who died during the induction period, we analyzed data on 382 patients, among whom 320 (83.8%) died. All time-varying exposures improved substantially the model's fit to data, relative to using only the time-invariant randomization group. All exposures indicated a protective effect for higher cumulative bevacizumab doses. The best-fitting WCE and TBC models accounted for both the cumulative effects and the different impact of doses taken at different times. CONCLUSIONS: All time-varying analyses, regardless of the exposure metric used, consistently suggested protective effects of higher cumulative bevacizumab doses. However, the results may partly reflect the presence of a confusion bias. Complementing the main ITT analysis of maintenance trials with an analysis of potential cumulative effects of treatment actually taken can provide new insights, but the results must be interpreted with caution because they do not benefit from the randomization. TRIAL REGISTRATION: clinicaltrials.gov, NCT00952029 . Registered 8 August 2009.

Modeling excess hazard with time-to-cure as a parameter.

Cure models have been widely developed to estimate the cure fraction when some subjects never experience the event of interest. However, these models were rarely focused on the estimation of the time-to-cure, that is, the delay elapsed between the diagnosis and "the time from which cure is reached," an important indicator, for instance, to address the question of access to insurance or loans for subjects with personal history of cancer. We propose a new excess hazard regression model that includes the time-to-cure as a covariate-dependent parameter to be estimated. The model is written similarly to a Beta probability distribution function and is shown to be a particular case of the non-mixture cure models. Parameters are estimated through a maximum likelihood approach and simulation studies demonstrate good performance of the model. Illustrative applications to three cancer data sets are provided and some limitations as well as possible extensions of the model are discussed. The proposed model offers a simple and comprehensive way to estimate more accurately the time-to-cure.

Cancer cure for 32 cancer types: results from the EUROCARE-5 study.

BACKGROUND: Few studies have estimated the probability of being cured for cancer patients. This study aims to estimate population-based indicators of cancer cure in Europe by type, sex, age and period. METHODS: 7.2 million cancer patients (42 population-based cancer registries in 17 European countries) diagnosed at ages 15-74 years in 1990-2007 with follow-up to 2008 were selected from the EUROCARE-5 dataset. Mixture-cure models were used to estimate: (i) life expectancy of fatal cases (LEF); (ii) cure fraction (CF) as proportion of patients with same death rates as the general population; (iii) time to cure (TTC) as time to reach 5-year conditional relative survival (CRS) >95%. RESULTS: LEF ranged from 10 years for chronic lymphocytic leukaemia patients to <6 months for those with liver, pancreas, brain, gallbladder and lung cancers. It was 7.7 years for patients with prostate cancer at age 65-74 years and >5 years for women with breast cancer. The CF was 94% for testis, 87% for thyroid cancer in women and 70% in men, 86% for skin melanoma in women and 76% in men, 66% for breast, 63% for prostate and <10% for liver, lung and pancreatic cancers. TTC was <5 years for testis and thyroid cancer patients diagnosed below age 55 years, and <10 years for stomach, colorectal, corpus uteri and melanoma patients of all ages. For breast and prostate cancers, a small excess (CRS < 95%) remained for at least 15 years. CONCLUSIONS: Estimates from this analysis should help to reduce unneeded medicalization and costs. They represent an opportunity to improve patients' quality of life.

Net survival in recurrence-free colon cancer patients.

PURPOSE: Conditional net survival in recurrence-free patients (CNS-RF) provides relevant clinical information and has never been assessed yet in a non-selected colon cancer population. We aimed to estimate conditional 5-year net survival in recurrence-free patients with colon cancer in the population-based Digestive Cancer Registry of Burgundy (France). METHODS: CNS-RF was estimated in the 3736 patients resected for cure for primary colon cancer between 1976 and 2006, using a flexible parametric model of net survival for every additional year survived at diagnosis and from 1 to 5 years thereafter. RESULTS: The net probability of surviving 5 more years increased from 72% at diagnosis to 92% for recurrence-free patients who survived 5 years after diagnosis. CNS-RF was over 90% 3 years after diagnosis in patients aged 75 and below. CNS-RF was over 95% in patients diagnosed after 2000 who were recurrence-free 3, 4 or 5 years after diagnosis. CNS-RF was similar between patients with stage I and II disease from 2 years after diagnosis and patients with stage III disease from 5 years after diagnosis. The initial differences in net survival related to gross features, clinical presentation, number of harvested nodes in stage II, and number of involved nodes in stage III disappeared after 2 years. CONCLUSIONS: CNS-RF is a relevant measure of prognosis in patients who have already achieved a period of remission. Providing an updated estimation of prognosis in the years following diagnosis may improve the survivors' quality of life and access to credit or insurance.

Time-to-cure and cure proportion in solid cancers in France. A population based study.

BACKGROUND: In cancer care, the cure proportion (P) and time-to-cure (TTC) are important indicators for practitioners, patients, and healthcare policy makers. The recent definition of TTC as the time at which the probability of belonging to the cured group reaches 95% was used for the first time. METHODS: The data stem from the common database of French cancer registries including 335,358 solid tumours diagnosed between 1995 and 2009 at 27 sites. P and TTC were estimated through a flexible parametric net survival cure model for each cancer site, sex, and age at diagnosis with acceptable assumption of cure (excess mortality rate ≤0.05). RESULTS: TTC was ≤5 years and P was >80% for skin melanoma and thyroid and testis cancers. It was 0 for testis cancer in men <55 and for thyroid cancer in men <45 and women <65. TTC was between 5 and 10 years for all digestive cancers except small intestine and all gynaecologic cancers except breast. It was ≥10 years in prostate, breast, and urinary tract. The range of P according to age and sex was 37-79% for urinary tract 72-88% for prostate and breast, 4-16% for pancreatic and 47-62% for colorectal cancer. CONCLUSION: Time-to-cure was estimated for the first time from a large national database and individual probabilities of cure. It was 0 in the younger patients with testis or thyroid cancer and <12 years in most cancer sites. These results should help improve access to credit and insurance for patients still alive past the estimated TTCs.

Impact of absence of consensual cutoff time distinguishing between synchronous and metachronous metastases: illustration with colorectal cancer.

Staging is essential for scientific exchanges on colorectal cancer. Lack of a consensual definition for synchronous and metachronous metastases for colorectal cancer may introduce artifactual differences between epidemiological studies according to stage. We investigated how variations in the cutoff for the definition of synchronous metastases influenced the stage-specific distribution and incidence and the survival of stage IV patients. Between 2007 and 2013, a total of 4636 cases of colorectal adenocarcinoma were registered in the cancer registry of Burgundy. Age-standardized incidence by stage was estimated for each cutoff from 0 to 12 months, differentiating between synchronous and metachronous metastases. Net survival was calculated from the date of the diagnosis of metastasis. The incidence of stage IV colorectal cancer increased from 6.0/100 000 when considering metastases diagnosed within the first month to 7.1/100 000 when including metastases diagnosed until 12 months after the diagnosis of colorectal cancer. When the cutoff increased from 1 to 12 months, the relative variation in the proportion of cancers was +21% for stage IV, -12% for stage III, and -5% for stage II. Similarly, the 1-year net survival for metachronous group was over 10% higher than that for the synchronous group when the cutoff was over 5 months. An objective definition of the relevant cutoff to distinguish between synchronous and metachronous metastases is required for scientific epidemiologic exchanges. Survival in the metachronous group was significantly better than survival in the synchronous group when the cutoff between synchronous and metachronous was over 4 months after the primary diagnosis.

A new approach to estimate time-to-cure from cancer registries data.

BACKGROUND: Cure models have been adapted to net survival context to provide important indicators from population-based cancer data, such as the cure fraction and the time-to-cure. However existing methods for computing time-to-cure suffer from some limitations. METHODS: Cure models in net survival framework were briefly overviewed and a new definition of time-to-cure was introduced as the time TTC at which P(t), the estimated covariate-specific probability of being cured at a given time t after diagnosis, reaches 0.95. We applied flexible parametric cure models to data of four cancer sites provided by the French network of cancer registries (FRANCIM). Then estimates of the time-to-cure by TTC and by two existing methods were derived and compared. Cure fractions and probabilities P(t) were also computed. RESULTS: Depending on the age group, TTC ranged from to 8 to 10 years for colorectal and pancreatic cancer and was nearly 12 years for breast cancer. In thyroid cancer patients under 55 years at diagnosis, TTC was strikingly 0: the probability of being cured was >0.95 just after diagnosis. This is an interesting result regarding the health insurance premiums of these patients. The estimated values of time-to-cure from the three approaches were close for colorectal cancer only. CONCLUSIONS: We propose a new approach, based on estimated covariate-specific probability of being cured, to estimate time-to-cure. Compared to two existing methods, the new approach seems to be more intuitive and natural and less sensitive to the survival time distribution.

An alternative classification to mixture modeling for longitudinal counts or binary measures.

Classifying patients according to longitudinal measures, or trajectory classification, has become frequent in clinical research. The k-means algorithm is increasingly used for this task in case of continuous variables with standard deviations that do not depend on the mean. One feature of count and binary data modeled by Poisson or logistic regression is that the variance depends on the mean; hence, the within-group variability changes from one group to another depending on the mean trajectory level. Mixture modeling could be used here for classification though its main purpose is to model the data. The results obtained may change according to the main objective. This article presents an extension of the k-means algorithm that takes into account the features of count and binary data by using the deviance as distance metric. This approach is justified by its analogy with the classification likelihood. Two applications are presented with binary and count data to show the differences between the classifications obtained with the usual Euclidean distance versus the deviance distance.

Operational Assessment of Long-Lasting Insecticidal Nets by Using an Anopheles Salivary Biomarker of Human-Vector Contact.

The widespread implementation of long-lasting insecticidal nets (LLINs) is a major intervention method for malaria control. Although the LLINs coverage increases, information available on the physical integrity (PI) of implemented LLINs is incomplete. This study aimed to validate human IgG antibody (Ab) response to Anopheles gSG6-P1 salivary peptide antigen, previously demonstrated as a pertinent biomarker of human exposure to Anopheles bites, for evaluating the PI of LLINs in field conditions. We analyzed data from 262 randomly selected children (< 5 years of age) in health districts of Benin. Anti-gSG6-P1 IgG responses were assessed and compared with the PI of LLINs that these same children slept under, and evaluated by the hole index (HI). Specific IgG levels were positively correlated to LLINs HI (r = 0.342; P < 0.0001). According to antipeptide IgG level (i.e., intensity of vector exposure), two categories of LLINs PI were defined: 1) group "HI: [0, 100]" corresponding to LLINs with "good" PI and 2) "HI > 100" corresponding to LLINs with "bad" PI. These results suggest that human Ab response to salivary peptide could be a complementary tool to help defining a standardized threshold of efficacy for LLINs under field use.

Behavioral cost & overdominance in Anopheles gambiae.

In response to the widespread use of control strategies such as Insecticide Treated Nets (ITN), Anopheles mosquitoes have evolved various resistance mechanisms. Kdr is a mutation that provides physiological resistance to the pyrethroid insecticides family (PYR). In the present study, we investigated the effect of the Kdr mutation on the ability of female An. gambiae to locate and penetrate a 1cm-diameter hole in a piece of netting, either treated with insecticide or untreated, to reach a bait in a wind tunnel. Kdr homozygous, PYR-resistant mosquitoes were the least efficient at penetrating an untreated damaged net, with about 51% [39-63] success rate compared to 80% [70-90] and 78% [65-91] for homozygous susceptible and heterozygous respectively. This reduced efficiency, likely due to reduced host-seeking activity, as revealed by mosquito video-tracking, is evidence of a recessive behavioral cost of the mutation. Kdr heterozygous mosquitoes were the most efficient at penetrating nets treated with PYR insecticide, thus providing evidence for overdominance, the rarely-described case of heterozygote advantage conveyed by a single locus. The study also highlights the remarkable capacity of female mosquitoes, whether PYR-resistant or not, to locate holes in bed-nets.

Impact of variability in adherence to HIV antiretroviral therapy on the immunovirological response and mortality.

BACKGROUND: Several previous studies have shown relationships between adherence to HIV antiretroviral therapy (ART) and the viral load, the CD4 cell count, or mortality. However, the impact of variability in adherence to ART on the immunovirological response does not seem to have been investigated yet. METHODS: Monthly adherence data (November 1999 to April 2009) from 317 HIV-1 infected patients enrolled in the Senegalese ART initiative were analyzed. Latent-class trajectory models were used to build typical trajectories for the average adherence and the standardized variance of adherence. The relationship between the standardized variance of adherence and each of the change in CD4 cell count, the change in viral load, and mortality were investigated using, respectively, a mixed linear regression, a mixed logistic regression, and a Cox model with time-dependent covariates. All the models were adjusted on the average adherence. RESULTS: Three latent trajectories for the average adherence and three for the standardized variance of adherence were identified. The increase in CD4 cell count and the increase in the percentage of undetectable viral loads were negatively associated with the standardized variance of adherence but positively associated with the average adherence. The risk of death decreased significantly with the increase in the average adherence but increased significantly with the increase of the standardized variance of adherence. CONCLUSIONS: The impacts of the level and the variability of adherence on the immunovirological response and survival justify the inclusion of these aspects into the process of patient education: adherence should be both high and constant.

Modeling the seasonality of Anopheles gambiae s.s. biting rates in a South Benin sanitary zone.

BACKGROUND: Efficient malaria vector control requires knowledge of spatio-temporal vector dynamics. We have classified village groups according to the biting rate profiles of both Anopheles coluzzii and An. gambiae, the major malaria vectors in these villages. METHODS: Mosquitoes were captured by human bait in 28 South Benin villages during 2009. Both An. coluzzii and An. gambiae counts in each village were standardized to focus on changes in the vector biting rate over time. Latent class trajectory modeling, allowing for random intercept at the 'village' level, was adjusted to standardized values. RESULTS: The villages could be classified into two groups with distinct vector biting rate profiles (continuous/transient). This classification helped creating a map of vector biting rates in the area. The biting rate profiles were found to be significantly correlated with mean rainfall, altitude, average number of larval sites, and average normalized difference vegetation index. CONCLUSIONS: In highly malaria-prone regions, knowledge of vector biting rate profiles is important to improve vector control interventions. A similar methodology may be applied to study the biting rate profiles of other vector-borne infections.

Evaluation of the effectiveness of malaria vector control measures in urban settings of Dakar by a specific anopheles salivary biomarker.

Standard entomological methods for evaluating the impact of vector control lack sensitivity in low-malaria-risk areas. The detection of human IgG specific to Anopheles gSG6-P1 salivary antigen reflects a direct measure of human-vector contact. This study aimed to assess the effectiveness of a range of vector control measures (VCMs) in urban settings by using this biomarker approach. The study was conducted from October to December 2008 on 2,774 residents of 45 districts of urban Dakar. IgG responses to gSG6-P1 and the use of malaria VCMs highly varied between districts. At the district level, specific IgG levels significantly increased with age and decreased with season and with VCM use. The use of insecticide-treated nets, by drastically reducing specific IgG levels, was by far the most efficient VCM regardless of age, season or exposure level to mosquito bites. The use of spray bombs was also associated with a significant reduction of specific IgG levels, whereas the use of mosquito coils or electric fans/air conditioning did not show a significant effect. Human IgG response to gSG6-P1 as biomarker of vector exposure represents a reliable alternative for accurately assessing the effectiveness of malaria VCM in low-malaria-risk areas. This biomarker tool could be especially relevant for malaria control monitoring and surveillance programmes in low-exposure/low-transmission settings.