Estimating the Effect of PrEP in Black Men Who Have Sex with Men: A Framework to Utilize Data from Multiple Non-Randomized Studies to Estimate Causal Effects

Black men who have sex with men (MSM) are disproportionately burdened by the HIV epidemic in the US. The effectiveness of pre-exposure prophylaxis (PrEP) in preventing HIV infection has been demonstrated through randomized placebo-controlled clinical trials in several populations. Importantly, no such trial has been conducted exclusively among Black MSM in the US, and it would be unethical and infeasible to do so now. To estimate the causal effects of PrEP access, initiation, and adherence on HIV risk, we utilized causal inference methods to combine data from two non-randomized studies that exclusively enrolled Black MSM. The estimated relative risks of HIV were: (i) 0.52 (95% confidence interval: 0.21, 1.22) for individuals with versus without PrEP access, (ii) 0.48 (0.12, 0.89) for individuals who initiated PrEP but were not adherent versus those who did not initiate, and (iii) 0.23 (0.02, 0.80) for individuals who were adherent to PrEP versus those who did not initiate. Beyond addressing the knowledge gap around the effect of PrEP in Black MSM in the US, which may have ramifications for public health, we have provided a framework to combine data from multiple non-randomized studies to estimate causal effects, which has broad utility.

Duration of viral infectiousness and correlation with symptoms and diagnostic testing in non-hospitalized adults during acute SARS-CoV-2 infection: A longitudinal cohort study

BACKGROUND

Guidelines for SARS-CoV-2 have relied on limited data on duration of viral infectiousness and correlation with COVID-19 symptoms and diagnostic testing.

METHODS

We enrolled ambulatory adults with acute SARS-CoV-2 infection and performed serial measurements of COVID-19 symptoms, nasal swab viral RNA, nucleocapsid (N) and spike (S) antigens, and replication-competent SARS-CoV-2 by viral growth in culture. We determined average time from symptom onset to a first negative test result and estimated risk of infectiousness, as defined by positive viral growth in culture.

RESULTS

Among 95 adults, median [interquartile range] time from symptom onset to first negative test result was 9 [5] days, 13 [6] days, 11 [4] days, and >19 days for S antigen, N antigen, culture growth, and viral RNA by RT-PCR, respectively. Beyond two weeks, virus growth and N antigen titers were rarely positive, while viral RNA remained detectable among half (26/51) of participants tested 21-30 days after symptom onset. Between 6-10 days from symptom onset, N antigen was strongly associated with culture positivity (relative risk=7.61, 95% CI: 3.01-19.22), whereas neither viral RNA nor symptoms were associated with culture positivity. During the 14 days following symptom onset, the presence of N antigen remained strongly associated (adjusted relative risk=7.66, 95% CI: 3.96-14.82) with culture positivity, regardless of COVID-19 symptoms.

CONCLUSIONS

Most adults have replication-competent SARS-CoV-2 for 10-14 after symptom onset. N antigen testing is a strong predictor of viral infectiousness and may be a more suitable biomarker, rather than absence of symptoms or viral RNA, to discontinue isolation within two weeks from symptom onset.

307. Diagnostic Test Kinetics, Infectivity, and Immunological Responses Among Unvaccinated Adults During Acute SARS-CoV-2 Infection

Background

Appropriate diagnostic testing can be used to inform infection control measures and reduce SARS-CoV-2 transmission, yet the test kinetics, infectivity, and immunological responses during acute, non-severe SARS-CoV-2 infection need clarity.

Methods

We conducted a prospective cohort study between Nov 2020-July 2021 in Seattle, Washington of 95 unvaccinated, immunocompetent adults with no prior SARS-CoV-2 infection. Nasal swabs (nasopharyngeal and anterior) and blood serum samples were serially collected at six visits over two months. Viral RNA, N and S antigen concentrations, and viral growth/infectivity were measured from nasal samples. Anti-S total antibody and IgG assays were performed on serum. We fit loess curves to quantitative data corresponding to each testing modality by days since symptom onset (DSSO) and compared qualitative test results across time points to demonstrate time-dependent agreement of PCR, N antigen, and culture results. Generalized estimating equations were used to approximate relative risk of culture positivity (a proxy for infectiousness) for positive vs. negative test results (antigen and PCR), stratified by presence/absence of symptoms and DSSO.

Sampling Schema

Nasal swabs and venous blood were collected at visits 1-4; venous blood only at visits 5-6. All participants were enrolled within 14 days of symptom onset (median: 6) and 7 days of a positive test (median: 4).

Results

Infections in this cohort (median age: 29y) were mild (no hospitalization). Median (IQR) time to negative result was 11 (4), 13 (6), and 20 (7) DSSO for culture growth, N antigen, and PCR tests, respectively. Viral RNA quantities declined more slowly than antigen and culturable virus; antibody titers rose rapidly 5-15 DSSO and plateaued 20-30 DSSO. All culture-positive samples collected 0-5 DSSO were positive by PCR, but relative risk of culture positivity (infectiousness) for positive vs. negative PCR results declined 6-10 DSSO. Relative risk of culture positivity for positive vs. negative antigen results was consistently high 0-10 DSSO, with similar results when stratified by presence of symptoms.

Diagnostic test kinetics and immunological responses

Diagnostic test kinetics and immunological responses measured in adults with non-severe, symptomatic SARS-CoV-2 infection: loess trendlines and 95% confidence intervals are given for SARS-CoV-2 viral load (calculated from PCR Ct value using a calibration curve), TCID50 from viral culture, mean concentrations of nucleocapsid and spike antigen proteins, and anti-S total and IgG antibody concentrations.

Conclusion

The results reinforce the importance of molecular PCR testing as a highly sensitive diagnostic tool but with limited utility as an indicator of viral culturability and likely infectiousness. N antigen testing may be a preferable diagnostic test within two weeks of symptom onset, especially 6-10 DSSO, because it more closely correlates with culture growth over the course of infection.

Disclosures

Daphne Hamilton, BA, Roche (spouse is employed by Roche): Employee Alexander L. Greninger, MD, PhD, Abbott: Contract Testing|Cepheid: Contract Testing|Gilead: Grant/Research Support|Gilead: Contract Testing|Hologic: Contract Testing|Merck: Grant/Research Support|Novavax: Contract Testing|Pfizer: Contract Testing Geoffrey S. Gottlieb, MD, PhD, Abbott Molecular Diagnostics: Grant/Research Support|Alere Technologies: Grant/Research Support|BMGF: Grant/Research Support|BMS: Grant/Research Support|Cerus Corp.: Grant/Research Support|Gilead Sciences: Grant/Research Support|Janssen Pharmaceutica: Grant/Research Support|Merck & Co: Grant/Research Support|Roche Molecular Systems: Grant/Research Support|THERA Technologies/TaiMed Biologics: Grant/Research Support|ViiV Healthcare: Grant/Research Support.

PrEP uptake and HIV viral suppression when PrEP is integrated into Ugandan ART clinics for HIV-negative members of HIV-serodifferent couples: A stepped wedge cluster randomized trial

Background

Global scale-up of HIV pre-exposure prophylaxis (PrEP) includes services to HIV-negative people in partnerships with people living with HIV (serodifferent couples). Data are needed on HIV outcomes, including uptake and adherence to PrEP and antiretroviral treatment (ART), to describe the impact of integrating PrEP into an existing HIV program.

Methods

Using a stepped-wedge cluster randomized trial design, we launched PrEP delivery for HIV-negative members of serodifferent couples in Uganda by integrating PrEP into existing ART programs for people living with HIV. The program provided PrEP training for ART providers, ongoing technical assistance, and a provisional supply chain mechanism for PrEP medication. Primary data on PrEP initiation, PrEP refills, ART initiation, and HIV viremia at 6 months (measured at 42-270 days) were collected through data abstraction of medical records from HIV-serodifferent couples sequentially enrolling at the ART clinics. Modified Poisson regression models, controlling for time and cluster, compared viral suppression (<1000 copies/ml) before and after launch of the PrEP program. This trial was registered at ClinicalTrials.gov, NCT03586128.

Findings

From June 1, 2018-December 15, 2020, 1,381 HIV-serodifferent couples were enrolled across 12 ART clinics in Kampala and Wakiso, Uganda, including 730 enrolled before and 651 after the launch of PrEP delivery. During the baseline period, 99.4% of partners living with HIV initiated ART and 85.0% were virally suppressed at 6 months. Among HIV-negative partners enrolled after PrEP launched, 81.0% (527/651) initiated PrEP within 90 days of enrolling; among these 527, 11.2% sought a refill 6 months later. In our powered intent-to-treat analysis, 82.1% and 76.7% of partners living with HIV were virally suppressed, respectively, which was not a statistically significant difference (RR=0.94, 95% CI: 0.82-1.07) and was stable across sensitivity analyses.

Interpretation

Integration of PrEP into ART clinics reached a high proportion of people in HIV-serodifferent relationships and did not improve the already high frequency of HIV viral suppression among partners living with HIV.

Funding

National Institute of Mental Health (R01MH110296).

Performance of anterior nares and tongue swabs for nucleic acid, Nucleocapsid, and Spike antigen testing for detecting SARS-CoV-2 against nasopharyngeal PCR and viral culture

OBJECTIVES

This study assesses and compares the performance of different swab types and specimen collection sites for SARS-CoV-2 testing, to reference standard real-time reverse transcriptase-polymerase chain reaction (RT-PCR) and viral culture.

METHODS

Symptomatic adults with COVID-19 who visited routine COVID-19 testing sites used spun polyester and FLOQSwabs to self-collect specimens from the anterior nares and tongue. We evaluated the self-collected specimen from anterior nares and tongue swabs for the nucleocapsid (N) or spike (S) antigen of SARS-CoV-2 by RT-PCR and then compared these results with results from RT-PCR and viral cultures from nurse-collected nasopharyngeal swabs.

RESULTS

Diagnostic sensitivity was highest for RT-PCR testing conducted using specimens from the anterior nares collected on FLOQSwabs (84%; 95% CI 68-94%) and spun polyester swabs (82%; 95% CI 66-92%), compared to RT-PCR tests conducted using specimens from nasopharyngeal swabs. Relative to viral culture from nasopharyngeal swabs, diagnostic sensitivities were higher for RT-PCR and antigen testing of anterior nares swabs (91-100%) than that of tongue swabs (18-81%). Antigen testing of anterior nares swabs had higher sensitivities against viral culture (91%) than against nasopharyngeal RT-PCR (38-70%). All investigational tests had high specificity compared with nasopharyngeal RT-PCR. Spun polyester swabs are equally effective as FLOQSwabs for anterior nasal RT-PCR testing.

CONCLUSIONS

We found that anterior nares specimens were more sensitive than tongue swab specimens or antigen testing for detecting SARS-CoV-2 by RT-PCR. Thus, self-collected anterior nares specimens may represent an alternative method for diagnostic SARS-CoV-2 testing in some settings.

Integrating PrEP delivery in public health family planning clinics: a protocol for a pragmatic stepped wedge cluster randomized trial in Kenya

Background

Adolescent girls and young women account for a disproportionate fraction of new HIV infections in Africa and are a priority population for HIV prevention, including provision of pre-exposure prophylaxis (PrEP). Anchoring PrEP delivery to care settings like family planning (FP) services that women already access routinely may offer an efficient platform to reach HIV at-risk women. However, context-specific implementation science evaluation is needed.

Methods

The Family Planning Plus Project is a prospective, pragmatic implementation evaluation, designed as a stepped wedge, cluster randomized trial, at 12 clinics in Kenya. In collaboration with the Kenya Ministry of Health and Kisumu County Department of Health, we will introduce integration of HIV risk screening and PrEP delivery in public health FP clinics. The core multifaceted implementation strategies to integrate PrEP in FP clinics will include: (1) PrEP delivery by existing FP clinic staff, (2) health provider training, (3) PrEP technical assistance to coach and mentor providers, (4) joint supervision with Kisumu County health officials, and (5) stakeholder engagement. All core components of PrEP delivery—including screening for HIV risk, HIV testing, dispensing, adherence and risk reduction counseling, assessment of side effects, and provision of refills, or safety assessment—will be conducted by existing FP clinic staff as part of a standard care service package. The goal is to catalyze sustainable scale-up within existing infrastructures beyond the project. We will rigorously evaluate implementation outcomes and impact, using the RE-AIM (Reach, Effectiveness, Adoption, Implementation, Maintenance) framework, and we will use Organizational Readiness for Implementing Change (ORIC) and the Consolidated Framework for Implementation Science Research (CFIR) to assess readiness to implement and contextual enablers and barriers of implementation, including how clinics innovate efficient delivery systems.

Discussion

Anchoring PrEP delivery to existing FP systems and staffing has tremendous potential to address barriers that women face in accessing HIV prevention and PrEP care, including lack of time, cost, and stigma of visiting a facility solely for HIV prevention. The FP Plus Project will initiate preparation for full-scale and sustainable model of integration of comprehensive HIV prevention services, including PrEP implementation, in public health FP clinics in low-income settings.

Trial registration

Registered with ClinicalTrials.gov on December 14, 2020: NCT04666792

Combining biomarkers by maximizing the true positive rate for a fixed false positive rate

Biomarkers abound in many areas of clinical research, and often investigators are interested in combining them for diagnosis, prognosis, or screening. In many applications, the true positive rate (TPR) for a biomarker combination at a prespecified, clinically acceptable false positive rate (FPR) is the most relevant measure of predictive capacity. We propose a distribution-free method for constructing biomarker combinations by maximizing the TPR while constraining the FPR. Theoretical results demonstrate desirable properties of biomarker combinations produced by the new method. In simulations, the biomarker combination provided by our method demonstrated improved operating characteristics in a variety of scenarios when compared with alternative methods for constructing biomarker combinations. Thus, use of our method could lead to the development of better biomarker combinations, increasing the likelihood of clinical adoption.

Developing biomarker combinations in multicenter studies via direct maximization and penalization

Motivated by a study of acute kidney injury, we consider the setting of biomarker studies involving patients at multiple centers where the goal is to develop a biomarker combination for diagnosis, prognosis, or screening. As biomarker studies become larger, this type of data structure will be encountered more frequently. In the presence of multiple centers, one way to assess the predictive capacity of a given combination is to consider the center-adjusted area under the receiver operating characteristic curve (aAUC), a summary of the ability of the combination to discriminate between cases and controls in each center. Rather than using a general method, such as logistic regression, to construct the biomarker combination, we propose directly maximizing the aAUC. Furthermore, it may be desirable to have a biomarker combination with similar performance across centers. To that end, we allow for penalization of the variability in the center-specific AUCs. We demonstrate desirable asymptotic properties of the resulting combinations. Simulations provide small-sample evidence that maximizing the aAUC can lead to combinations with improved performance. We also use simulated data to illustrate the utility of constructing combinations by maximizing the aAUC while penalizing variability. Finally, we apply these methods to data from the study of acute kidney injury.

Combined Utility of 25 Disease and Risk Factor Polygenic Risk Scores for Stratifying Risk of All-Cause Mortality

While genome-wide association studies have identified susceptibility variants for numerous traits, their combined utility for predicting broad measures of health, such as mortality, remains poorly understood. We used data from the UK Biobank to combine polygenic risk scores (PRS) for 13 diseases and 12 mortality risk factors into sex-specific composite PRS (cPRS). These cPRS were moderately associated with all-cause mortality in independent data within the UK Biobank: the estimated hazard ratios per standard deviation were 1.10 (95% confidence interval: 1.05, 1.16) and 1.15 (1.10, 1.19) for women and men, respectively. Differences in life expectancy between the top and bottom 5% of the cPRS were estimated to be 4.79 (1.76, 7.81) years and 6.75 (4.16, 9.35) years for women and men, respectively. These associations were substantially attenuated after adjusting for non-genetic mortality risk factors measured at study entry (i.e., middle age for most participants). The cPRS may be useful in counseling younger individuals at higher genetic risk of mortality on modification of non-genetic factors.

Case-Only Analysis of Gene-Environment Interactions Using Polygenic Risk Scores

Investigations of gene (G)-environment (E) interactions have led to limited findings to date, possibly due to weak effects of individual genetic variants. Polygenic risk scores (PRS), which capture the genetic susceptibility associated with a set of variants, can be a powerful tool for detecting global patterns of interaction. Motivated by the case-only method for evaluating interactions with a single variant, we propose a case-only method for the analysis of interactions with a PRS in case-control studies. Assuming the PRS and E are independent, we show how a linear regression of the PRS on E in a sample of cases can be used to efficiently estimate the interaction parameter. Furthermore, if an estimate of the mean of the PRS in the underlying population is available, the proposed method can estimate the PRS main effect. Extensions allow for PRS-E dependence due to associations between variants in the PRS and E. Simulation studies indicate the proposed method offers appreciable gains in efficiency over logistic regression and can recover much of the efficiency of a cohort study. We applied the proposed method to investigate interactions between a PRS and epidemiologic factors on breast cancer risk in the UK Biobank (United Kingdom, recruited 2006-2010).

Biomarker combinations for diagnosis and prognosis in multicenter studies: Principles and methods

Many investigators are interested in combining biomarkers to predict a binary outcome or detect underlying disease. This endeavor is complicated by the fact that many biomarker studies involve data from multiple centers. Depending upon the relationship between center, the biomarkers, and the target of prediction, care must be taken when constructing and evaluating combinations of biomarkers. We introduce a taxonomy to describe the role of center and consider how a biomarker combination should be constructed and evaluated. We show that ignoring center, which is frequently done by clinical researchers, is often not appropriate. The limited statistical literature proposes using random intercept logistic regression models, an approach that we demonstrate is generally inadequate and may be misleading. We instead propose using fixed intercept logistic regression, which appropriately accounts for center without relying on untenable assumptions. After constructing the biomarker combination, we recommend using performance measures that account for the multicenter nature of the data, namely the center-adjusted area under the receiver operating characteristic curve. We apply these methods to data from a multicenter study of acute kidney injury after cardiac surgery. Appropriately accounting for center, both in construction and evaluation, may increase the likelihood of identifying clinically useful biomarker combinations.

Using ordinal outcomes to construct and select biomarker combinations for single-level prediction

BACKGROUND

Biomarker studies may involve an ordinal outcome, such as no, mild, or severe disease. There is often interest in predicting one particular level of the outcome due to its clinical significance.

METHODS

A simple approach to constructing biomarker combinations in this context involves dichotomizing the outcome and using a binary logistic regression model. We assessed whether more sophisticated methods offer advantages over this simple approach. It is often necessary to select among several candidate biomarker combinations. One strategy involves selecting a combination based on its ability to predict the outcome level of interest. We propose an algorithm that leverages the ordinal outcome to inform combination selection. We apply this algorithm to data from a study of acute kidney injury after cardiac surgery, where kidney injury may be absent, mild, or severe.

RESULTS

Using more sophisticated modeling approaches to construct combinations provided gains over the simple binary logistic regression approach in specific settings. In the examples considered, the proposed algorithm for combination selection tended to reduce the impact of bias due to selection and to provide combinations with improved performance.

CONCLUSIONS

Methods that utilize the ordinal nature of the outcome in the construction and/or selection of biomarker combinations have the potential to yield better combinations.

Evaluating biomarkers for prognostic enrichment of clinical trials

BACKGROUND/AIMS

A potential use of biomarkers is to assist in prognostic enrichment of clinical trials, where only patients at relatively higher risk for an outcome of interest are eligible for the trial. We investigated methods for evaluating biomarkers for prognostic enrichment.

METHODS

We identified five key considerations when considering a biomarker and a screening threshold for prognostic enrichment: (1) clinical trial sample size, (2) calendar time to enroll the trial, (3) total patient screening costs and the total per-patient trial costs, (4) generalizability of trial results, and (5) ethical evaluation of trial eligibility criteria. Items (1)-(3) are amenable to quantitative analysis. We developed the Biomarker Prognostic Enrichment Tool for evaluating biomarkers for prognostic enrichment at varying levels of screening stringency.

RESULTS

We demonstrate that both modestly prognostic and strongly prognostic biomarkers can improve trial metrics using Biomarker Prognostic Enrichment Tool. Biomarker Prognostic Enrichment Tool is available as a webtool at http://prognosticenrichment.com and as a package for the R statistical computing platform.

CONCLUSION

In some clinical settings, even biomarkers with modest prognostic performance can be useful for prognostic enrichment. In addition to the quantitative analysis provided by Biomarker Prognostic Enrichment Tool, investigators must consider the generalizability of trial results and evaluate the ethics of trial eligibility criteria.

Urinalysis findings and urinary kidney injury biomarker concentrations

Introduction

Urinary biomarkers of kidney injury are presumed to reflect renal tubular damage. However, their concentrations may be influenced by other factors, such as hematuria or pyuria. We sought to examine what non-injury related urinalysis factors are associated with urinary biomarker levels.

Methods

We examined 714 adults who underwent cardiac surgery in the TRIBE-AKI cohort that did not experience post-operative clinical AKI (patients with serum creatinine change of ≥ 20% were excluded). We examined the association between urinalysis findings and the pre- and first post-operative urinary concentrations of 4 urinary biomarkers: neutrophil gelatinase-associated lipocalin (NGAL), interleukin-18 (IL-18), kidney injury molecule-1 (KIM-1), and liver fatty acid binding protein (L-FABP).

Results

The presence of leukocyte esterase and nitrites on urinalysis was associated with increased urinary NGAL (R² 0.16, p < 0.001 and R² 0.07, p < 0.001, respectively) in pre-operative samples. Hematuria was associated with increased levels of all 4 biomarkers, with a much stronger association seen in post-operative samples (R² between 0.02 and 0.21). Dipstick proteinuria concentrations correlated with levels of all 4 urinary biomarkers in pre-operative and post-operative samples (R² between 0.113 and 0.194 in pre-operative and between 0.122 and 0.322 in post-operative samples). Adjusting the AUC of post-operative AKI for dipstick proteinuria lowered the AUC for all 4 biomarkers at the pre-operative time point and for 2 of the 4 biomarkers at the post-operative time point.

Conclusions

Several factors available through urine dipstick testing are associated with increased urinary biomarker concentrations that are independent of clinical kidney injury. Future studies should explore the impact of these factors on the prognostic and diagnostic performance of these AKI biomarkers.

Electronic supplementary material

The online version of this article (doi:10.1186/s12882-017-0629-z) contains supplementary material, which is available to authorized users.

Validity of a Neurological Scoring System for Canine X-Linked Myotubular Myopathy

A simple clinical neurological test was developed to evaluate response to gene therapy in a preclinical canine model of X-linked myotubular myopathy (XLMTM). This devastating congenital myopathy is caused by mutation in the myotubularin (MTM1) gene. Clinical signs include muscle weakness, early respiratory failure, and ventilator dependence. A spontaneously occurring canine model has a similar clinical picture and histological abnormalities on muscle biopsy compared with patients. We developed a neuromuscular assessment score, graded on a scale from 10 (normal) to 1 (unable to maintain sternal recumbency). We hypothesize that this neurological assessment score correlates with genotype and established measures of disease severity and is reliable when performed by an independent observer. At 17 weeks of age, there was strong correlation between neurological assessment scores and established methods of severity testing. The neurological severity score correctly differentiated between XLMTM and wild-type dogs with good interobserver reliability, on the basis of strong agreement between neurological scores assigned by independent observers. Together, these data indicate that the neurological scoring system developed for this canine congenital neuromuscular disorder is reliable and valid. This scoring system may be helpful in evaluating response to therapy in preclinical testing in this disease model, such as response to gene therapy.

Pre-diagnostic circulating sex hormone levels and risk of prostate cancer by TMPRSS2:ERG status

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Background: Experimental studies have shown that androgen receptor stimulation can facilitate formation of the TMPRSS2:ERG gene fusion in prostate cell lines. No study has tested whether higher pre-diagnostic circulating sex hormone levels in men increase the risk of developing TMPRSS2:ERG positive prostate cancer specifically. Methods: We conducted a nested case-control study of 200 prostate cancer cases and 1,057 controls from the Physicians’ Health Study and Health Professionals Follow-up Study. We examined associations between pre-diagnostic circulating levels of total testosterone, free testosterone, DHT, androstanediol glucuronide, estradiol, and SHBG and risk of prostate cancer by TMPRSS2:ERG status. TMPRSS2:ERG was assessed by ERG immunohistochemistry. We used multivariable unconditional polytomous logistic regression to calculate odds ratios (ORs) and 95% confidence intervals (CIs) for risk of fusion-positive (n = 94) and, separately, fusion-negative (n = 106) disease. Results: Free testosterone was significantly associated with the risk of ERG-positive prostate cancer (OR: 1.37, 95% CI: 1.05-1.77), but not ERG-negative prostate cancer (OR: 1.09, 95% CI: 0.86-1.38) (p-diff: 0.17). None of the remaining hormones evaluated showed clear differential associations with ERG-positive versus ERG-negative disease. Conclusions: These findings provide some suggestive evidence that higher pre-diagnostic free testosterone levels are associated with an increased risk of developing TMPRSS2:ERG positive prostate cancer but are not associated with prostate cancer that lacks TMPRSS2:ERG.

RiGoR: reporting guidelines to address common sources of bias in risk model development

Reviewing the literature in many fields on proposed risk models reveals problems with the way many risk models are developed. Furthermore, papers reporting new risk models do not always provide sufficient information to allow readers to assess the merits of the model. In this review, we discuss sources of bias that can arise in risk model development. We focus on two biases that can be introduced during data analysis. These two sources of bias are sometimes conflated in the literature and we recommend the terms resubstitution bias and model-selection bias to delineate them. We also propose the RiGoR reporting standard to improve transparency and clarity of published papers proposing new risk models.

Androgen receptor CAG repeat polymorphism and risk of TMPRSS2:ERG-positive prostate cancer

BACKGROUND

The androgen receptor (AR) is an essential gene in prostate cancer pathogenesis and progression. Genetic variation in AR exists, including a polymorphic CAG repeat sequence that is inversely associated with transcriptional activity. Experimental data suggest that heightened AR activity facilitates formation of TMPRSS2:ERG, a gene fusion present in approximately 50% of tumors of patients with prostate cancer.

METHODS

We undertook a nested case-control study to investigate the hypothesis that shorter CAG repeat length would be associated with prostate cancer risk defined by TMPRSS2:ERG status. The study included 291 men with prostate cancer (147 ERG-positive) and 1,221 cancer-free controls. ORs and 95% confidence intervals (CI) were calculated using logistic regression.

RESULTS

Median CAG repeat length (interquartile range) among controls was 22 (20-24). Men with shorter CAG repeats had an increased risk of ERG-positive (OR, 1.07 per 1 repeat decrease; 95% CI, 1.00-1.14), but not ERG-negative prostate cancer (OR, 0.99 per 1 repeat decrease; 95% CI, 0.93-1.05).

CONCLUSIONS

These data suggest that shorter CAG repeats are specifically associated with development of TMPRSS2:ERG-positive prostate cancer.

IMPACT

Our results provide supportive evidence that androgen signaling underlies the development of prostate tumors that harbor TMPRSS2:ERG. Moreover, these results suggest that TMPRSS2:ERG may represent a unique molecular subtype of prostate cancer with an etiology distinct from TMPRSS2:ERG-negative disease.

Developing risk prediction models for kidney injury and assessing incremental value for novel biomarkers

The field of nephrology is actively involved in developing biomarkers and improving models for predicting patients' risks of AKI and CKD and their outcomes. However, some important aspects of evaluating biomarkers and risk models are not widely appreciated, and statistical methods are still evolving. This review describes some of the most important statistical concepts for this area of research and identifies common pitfalls. Particular attention is paid to metrics proposed within the last 5 years for quantifying the incremental predictive value of a new biomarker.

Modification of the association between obesity and lethal prostate cancer by TMPRSS2:ERG

BACKGROUND

TMPRSS2:ERG is a hormonally regulated gene fusion present in about half of prostate tumors. We investigated whether obesity, which deregulates several hormonal pathways, interacts with TMPRSS2:ERG to impact prostate cancer outcomes.

METHODS

The study included 1243 participants in the prospective Physicians' Health Study and Health Professionals Follow-Up Study diagnosed with prostate cancer between 1982 and 2005. ERG overexpression (a TMPRSS2:ERG marker) was assessed by immunohistochemistry of tumor tissue from radical prostatectomy or transurethral resection of the prostate. Body mass index (BMI) and waist circumference, measured on average 1.3 years and 5.3 years before diagnosis, respectively, were available from questionnaires. Data on BMI at baseline was also available. We used Cox regression to calculate hazard ratios and 95% confidence intervals (CIs). All statistical tests were two-sided.

RESULTS

During a mean follow-up of 12.8 years, 119 men developed lethal disease (distant metastases or prostate cancer death). Among men with ERG-positive tumors, the multivariable hazard ratio for lethal prostate cancer was 1.48 (95% CI = 0.98 to 2.23) per 5-unit increase in BMI before diagnosis, 2.51 (95% CI = 1.26 to 4.99) per 8-inch increase in waist circumference before diagnosis, and 2.22 (95% CI = 1.35 to 3.63) per 5-unit increase in BMI at baseline. The corresponding hazard ratios among men with ERG-negative tumors were 1.10 (95% CI = 0.76 to1.59; P interaction = .24), 1.14 (95% CI = 0.62 to 2.10; P interaction = .09), and 0.78 (95% CI = 0.52 to 1.19; P interaction = .001).

CONCLUSIONS

These results suggest that obesity is linked with poorer prostate cancer prognosis primarily in men with tumors harboring the gene fusion TMPRSS2:ERG.

Abstract LB-28: The IGF/insulin signaling axis TMPRSS2:ERG and prostate cancer survival

Background: One half of prostate cancers harbor the TMPRSS2:ERG fusion, a somatic event that may reflect a distinct disease molecular subtype. TMPRSS2 is androgen regulated and ERG is a transcription factor that is part of the ETS family. Based on experimental evidence, we hypothesized that TMPRSS2:ERG tumors would be more sensitive to the insulin like growth factor (IGF)/insulin signaling axis in prostate cancer survival.

Methods: We studied participants in the prospective Physicians' Health Study (PHS) and the Health Professionals Follow-Up Study (HPFS) diagnosed with prostate cancer from 1982 - 2005. TMPRSS2:ERG was assessed in tumor tissue microarrays by immunohistochemical evaluation of ERG expression (n=1,236). Pre-diagnostic plasma concentrations of IGF1 (n=307), IGFBP3 (n=307), c-peptide (n=293), and adiponectin (n=120), and tissue expression of the IGF1 receptor (IGF1R; n=713), insulin receptor (IR; n=682), and adionectin receptor (AdipoR2; n=840) were available among men with measured ERG expression. Men have been followed for biochemical recurrence and cancer mortality through 2012. We used Cox regression to estimate hazard ratios (HRs) and 95% confidence intervals (CI) of associations between circulating biomarkers, TMPRSS2:ERG and prostate cancer outcomes.

Results: Mean follow-up for lethal prostate cancer was 12.8 years and for recurrence 11.1 years. The number of lethal and recurrence events among men with measured blood markers were: IGF1/IGFBP3 25 and 61, c-peptide 20 and 56, and adiponectin 9 and 17, respectively. Among ERG negative tumors, comparing high vs. low concentrations, the multivariable HR for recurrence was 0.4 (95% CI 0.2-1.1) for IGF1, 1.1 (95% CI 0.5-2.8) for IGFBP3, 1.6 (95% CI 0.7-3.6) for c-peptide, and 1.4 (95% CI 0.3-5.6) for adiponectin. The corresponding HRs among ERG positive tumors were 1.8 (95% CI 0.8-4.0; p interaction 0.04) for IGF1, 0.8 (95% CI 0.4-1.8; p interaction 0.61) for IGFBP3, 0.6 (95% CI 0.3-1.3; p interaction 0.16) for c-peptide, and 0.8 (95% CI 0.2-3.6; p interaction 0.53) for adiponectin. Among ERG negative tumors, comparing high vs. low concentrations of the blood markers, the multivariable HR for lethal disease was 0.7 (95% CI 0.2-3.2) for IGF1, 1.4 (95% CI 0.3-5.9) for IGFBP3, 3.64 (95% CI 0.6-20.9) for c-peptide, and 1.1 (95% CI 0.2-7.8) for adiponectin. The corresponding HRs among ERG positive tumors were 2.3 (95% CI 0.5-11.1; p interaction 0.53) for IGF1, 0.6 (95% CI 0.1-2.3; p interaction 0.86) for IGFBP3, 0.7 (95% CI 0.2-2.9; p interaction 0.37) for c-peptide, and 0.4 (95% CI 0.03-5.4; p interaction 0.44) for adiponectin. The expression of IR, IGF1R, and AdipoR2 were significantly (all p-values &lt;0.01) higher in ERG positive vs. negative tumors.

Conclusions: Although the number of events were relatively small, our results support the hypothesis that TMPRSS2:ERG fusion may modify the association between the IGF/insulin signaling axis and prostate cancer prognosis.

Citation Format: Thomas U. Ahearn, Andreas Pettersson, Edward C. Stack, Jing Ma, Travis Gerke, Allison Meisner, Michael N. Pollak, Stephen Finn, Meir J. Stampfer, Massimo Loda, Edward L. Giovannucci, Lorelei A. Mucci. The IGF/insulin signaling axis TMPRSS2:ERG and prostate cancer survival. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr LB-28. doi:10.1158/1538-7445.AM2013-LB-28

A single nucleotide polymorphism in inflammatory gene RNASEL predicts outcome after radiation therapy for localized prostate cancer

PURPOSE

To study associations between single nucleotide polymorphisms (SNP) in Ribonuclease L (RNASEL), a gene implicated in inflammation and prostate cancer risk, and outcomes after radiation therapy.

EXPERIMENTAL DESIGN

We followed participants in the prospective US Health Professionals Follow-Up Study treated with radiation therapy for early-stage prostate cancer. Three SNPs were genotyped based on previously determined functional and biological significance. We used multivariable Cox proportional hazards models to assess per-allele associations with the primary outcome defined as time to a composite endpoint including development of lethal prostate cancer or biochemical recurrence.

RESULTS

We followed 434 patients treated with radiation therapy for a median of 9 years. On multivariate analysis, the rs12757998 variant allele was associated with significantly decreased risk of the composite endpoint [HR: 0.65; 95% confidence interval (CI), 0.45-0.94%; P = 0.02] driven by decreased biochemical recurrence (HR: 0.60; 95% CI, 0.40-0.89%; P = 0.01) and men treated with external beam (HR: 0.58; 95% CI, 0.36-0.93%; P = 0.02). In contrast, in 516 men from the same cohort treated with radical prostatectomy, we found no significant impact of this variant on outcome. Furthermore, the rs12757998 variant allele significantly modified the association between androgen deprivation therapy and outcomes after radiation therapy (p-interaction = 0.02).

CONCLUSION

We show an association between RNASEL SNP rs12757998 and outcome after radiation therapy for prostate cancer. This SNP is associated with increased circulating C-reactive protein and interleukin-6, suggesting a potential role for inflammation in the response to radiation. If validated, genetic predictors of outcome may help inform prostate cancer management.

CD4 helper T cells, CD8 cytotoxic T cells, and FOXP3(+) regulatory T cells with respect to lethal prostate cancer

Prostate cancer represents a major contributor to cancer mortality, but the majority of men with prostate cancer will die of other causes. Thus, a challenge is identifying potentially lethal disease at diagnosis. Conflicting results have been reported when investigating the relationship between infiltration of lymphocytes and survival in prostate cancer. One of the mechanisms suggested is the recruitment of regulatory T cells (T(regs)), a subpopulation of T cells that have a role in promoting tumor growth. T(regs) counteract tumor rejection through suppressive functions on the anti-immune response but their prognostic significance is still unknown. We report here the results of a conducted case-control study nested in a cohort of men treated with transurethral resection of the prostate and diagnosed incidentally with prostate cancer. Cases are men who died of prostate cancer (n=261) and controls are men who survived >10 years after their diagnosis (n=474). Infiltration of both T(helper) and T(cytotoxic) cells was frequently observed and the majority of the T(regs) were CD4(+). T(helper) or T(cytotoxic) cells were not associated with lethal prostate cancer. However, we found a nearly twofold increased risk of lethal prostate cancer when comparing the highest with the lowest quartile of CD4(+) T(regs) cells (95% confidence interval: 1.3-2.9). Our conclusion is that men with greater numbers of CD4(+) T(regs) in their prostate tumor environment have an increased risk of dying of prostate cancer. Identification of CD4(+) T(regs) in tumor tissue may predict clinically relevant disease at time of diagnosis independently of other clinical factors.

A repeated measures model for analysis of continuous outcomes in sequential parallel comparison design studies

Previous authors have proposed the sequential parallel comparison design (SPCD) to address the issue of high placebo response rate in clinical trials. The original use of SPCD focused on binary outcomes, but recent use has since been extended to continuous outcomes that arise more naturally in many fields, including psychiatry. Analytic methods proposed to date for analysis of SPCD trial continuous data included methods based on seemingly unrelated regression and ordinary least squares. Here, we propose a repeated measures linear model that uses all outcome data collected in the trial and accounts for data that are missing at random. An appropriate contrast formulated after the model has been fit can be used to test the primary hypothesis of no difference in treatment effects between study arms. Our extensive simulations show that when compared with the other methods, our approach preserves the type I error even for small sample sizes and offers adequate power and the smallest mean squared error under a wide variety of assumptions. We recommend consideration of our approach for analysis of data coming from SPCD trials.

L-methylfolate as adjunctive therapy for SSRI-resistant major depression: results of two randomized, double-blind, parallel-sequential trials

OBJECTIVE

The authors conducted two multicenter sequential parallel comparison design trials to investigate the effect of L-methylfolate augmentation in the treatment of major depressive disorder in patients who had a partial response or no response to selective serotonin reuptake inhibitors (SSRIs).

METHOD

In the first trial, 148 outpatients with SSRI-resistant major depressive disorder were enrolled in a 60-day study divided into two 30-day periods. Patients were randomly assigned, in a 2:3:3 ratio, to receive L-methylfolate for 60 days (7.5 mg/day for 30 days followed by 15 mg/day for 30 days), placebo for 30 days followed by L-methylfolate (7.5 mg/day) for 30 days, or placebo for 60 days. SSRI dosages were kept constant throughout the study. In the second trial, with 75 patients, the design was identical to the first, except that the l-methylfolate dosage was 15 mg/day during both 30-day periods.

RESULTS

In the first trial, no significant difference was observed in outcomes between the treatment groups. In the second trial, adjunctive L-methylfolate at 15 mg/day showed significantly greater efficacy compared with continued SSRI therapy plus placebo on both primary outcome measures (response rate and degree of change in depression symptom score) and two secondary outcome measures of symptom severity. The number needed to treat for response was approximately six in favor of adjunctive L-methylfolate at 15 mg/day. L-Methylfolate was well tolerated, with rates of adverse events no different from those reported with placebo.

CONCLUSIONS

Adjunctive L-methylfolate at 15 mg/day may constitute an effective, safe, and relatively well tolerated treatment strategy for patients with major depressive disorder who have a partial response or no response to SSRIs.

A 12-week, randomized, double-blind, placebo-controlled, sequential parallel comparison trial of ziprasidone as monotherapy for major depressive disorder

OBJECTIVE

To study ziprasidone monotherapy for major depressive disorder, defined according to the DSM-IV.

METHOD

One hundred twenty outpatients were enrolled between June 2008 and September 2010 in a 12-week study that was divided into two 6-week periods according to the sequential parallel comparison design. Patients were randomized in a 2:3:3 fashion to receive ziprasidone for 12 weeks, placebo for 6 weeks followed by ziprasidone for 6 weeks, or placebo for 12 weeks. The main outcome measure was the 17-item Hamilton Depression Rating Scale (HDRS-17), with the Quick Inventory of Depressive Symptomatology, Self-Rated (QIDS-SR), and Clinical Global Impressions-Severity of Illness scale (CGI-S) serving as the study secondary measures.

RESULTS

One hundred twenty patients (53 women [44.1%]) were randomized to treatment. The mean (SD) age of these patients was 43.7 (11.0) years. Mean (SD) baseline HDRS-17, CGI-S, and QIDS-SR scores were 19.9 (5.0), 4.3 (0.6), and 15.6 (3.0), respectively. There was no statistically significant difference in reduction of depressive symptoms, response rates, or remission rates between ziprasidone- or placebo-treated patients. This was true for both the study primary as well as secondary outcome scales.

CONCLUSIONS

In conclusion, treatment with ziprasidone monotherapy was not associated with any statistically significant advantage in efficacy over placebo. Although studies involving larger sample size would be required to have adequate statistical power to detect treatment differences smaller than 2.5 points on the HDRS-17, such differences would be of questionable clinical relevance.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT00555997.

Variations in common carotid artery intima-media thickness during the cardiac cycle: implications for cardiovascular risk assessment

BACKGROUND

Common carotid artery intima-media thickness (IMT), a measure of atherosclerosis, varies between peak systole and end-diastole. This difference might affect cardiovascular risk assessment.

METHODS

IMT measurements of the right and left common carotid arteries were synchronized with an electrocardiogram, using the R wave for end-diastole and the T wave for peak systole. IMT was measured in 2,930 members of the Framingham Offspring Study. Multivariate regression models were generated with end-diastolic IMT, peak systolic IMT, and change in IMT as dependent variables and Framingham risk factors as independent variables. End-diastolic IMT estimates were compared with the upper quartile of IMT on the basis of normative data obtained at peak systole.

RESULTS

The average age of the study population was 57.9 years. The average difference in IMT during the cardiac cycle was 0.037 mm (95% confidence interval, 0.035-0.038 mm). End-diastolic IMT and peak systolic IMT had similar associations with Framingham risk factors (total R(2) = 0.292 vs 0.275) and were significantly associated with all risk factors. In a fully adjusted multivariate model, thinner IMT at peak systole was associated with pulse pressure (P < .0001), low-density lipoprotein cholesterol (P = .0064), age (P = .046), and no other risk factors. Performing end-diastolic IMT measurements while using upper quartile peak systolic IMT normative data led to inappropriately increasing by 42.1% the number of individuals in the fourth IMT quartile (high cardiovascular risk category).

CONCLUSION

The difference in IMT between peak systole and end diastole is associated with pulse pressure, low-density lipoprotein cholesterol, and age. In this study, the mean IMT difference during the cardiac cycle led to an overestimation by 42.1% of individuals at high risk for cardiovascular disease.

Adjustment of the GRACE score by growth differentiation factor 15 enables a more accurate appreciation of risk in non-ST-elevation acute coronary syndrome

AIMS

The aim of the study was to evaluate whether knowledge of the circulating concentration of growth differentiation factor 15 (GDF-15) adds predictive information to the Global Registry of Acute Coronary Events (GRACE) score, a validated scoring system for risk assessment in non-ST-elevation acute coronary syndrome (NSTE-ACS). We also evaluated whether GDF-15 adds predictive information to a model containing the GRACE score and N-terminal pro-B-type natriuretic peptide (NT-proBNP), a prognostic biomarker already in clinical use.

METHODS AND RESULTS

The GRACE score, GDF-15, and NT-proBNP levels were determined on admission in 1122 contemporary patients with NSTE-ACS. Six-month all-cause mortality or non-fatal myocardial infarction (MI) was the primary endpoint of the study. To obtain GDF-15- and NT-proBNP-adjusted 6-month estimated probabilities of death or non-fatal MI, statistical algorithms were developed in a derivation cohort (n = 754; n = 66 reached the primary endpoint) and applied to a validation cohort (n = 368; n = 33). Adjustment of the GRACE risk estimate by GDF-15 increased the area under the receiver-operating characteristic curve (AUC) from 0.79 to 0.85 (P < 0.001) in the validation cohort. Discrimination improvement was confirmed by an integrated discrimination improvement (IDI) of 0.055 (P = 0.005). A net 31% of the patients without events were reclassified into lower risk, and a net 27% of the patients with events were reclassified into higher risk, resulting in a total continuous net reclassification improvement [NRI(>0)] of 0.58 (P = 0.002). Addition of NT-proBNP to the GRACE score led to a similar improvement in discrimination and reclassification. Addition of GDF-15 to a model containing GRACE and NT-proBNP led to a further improvement in model performance [increase in AUC from 0.84 for GRACE plus NT-proBNP to 0.86 for GRACE plus NT-proBNP plus GDF-15, P = 0.010; IDI = 0.024, P = 0.063; NRI(>0) = 0.42, P = 0.022].

CONCLUSION

We show that a single measurement of GDF-15 on admission markedly enhances the predictive value of the GRACE score and provides moderate incremental information to a model including the GRACE score and NT-proBNP. Our study is the first to provide simple algorithms that can be used by the practicing clinician to more precisely estimate risk in individual patients based on the GRACE score and a single biomarker measurement on admission. The rigorous statistical approach taken in the present study may serve as a blueprint for future studies exploring the added value of biomarkers beyond clinical risk scores.

Associations of carotid artery intima-media thickness (IMT) with risk factors and prevalent cardiovascular disease: comparison of mean common carotid artery IMT with maximum internal carotid artery IMT

OBJECTIVE

The goal of this study was to compare internal carotid artery (ICA) intima-media thickness (IMT) with common carotid artery (CCA) IMT as global markers of cardiovascular disease (CVD).

METHODS

Cross-sectional measurements of the mean CCA IMT and maximum ICA IMT were made on ultrasound images acquired from the Framingham Offspring cohort (n = 3316; mean age, 58 years; 52.7% women). Linear regression models were used to study the associations of the Framingham risk factors with CCA and ICA IMT. Multivariate logistic regression models and receiver operating characteristic (ROC) curve analysis were used to compare the associations of prevalent CVD with CCA and ICA IMT and determine sensitivity and specificity.

RESULTS

The association between age and the mean CCA IMT corresponded to an increase of 0.007 mm/y; the increase was 0.037 mm/y for the ICA IMT. Framingham risk factors accounted for 28.6% and 27.5% of the variability in the CCA and ICA IMT, respectively. Age and gender contributed 23.5% to the variability of the CCA IMT and 22.5% to that of the ICA IMT, with the next most important factor being systolic blood pressure (1.9%) for the CCA IMT and smoking (1.6%) for the ICA IMT. The CCA IMT and ICA IMT were statistically significant predictors of prevalent CVD, with the ICA IMT having a larger area under the ROC curve (0.756 versus 0.695).

CONCLUSIONS

Associations of risk factors with CCA and ICA IMT are slightly different, and both are independently associated with prevalent CVD. Their value for predicting incident cardiovascular events needs to be compared in outcome studies.

GPR30 and HER-2 Expression in Invasive and Metastatic Breast Cancer

Background: GPR30 expression, a new estrogen receptor, has been previously associated with HER-2, tumor size and metastasis in invasive breast cancer (BC) but its role in paired normal (N), invasive (I), and metastatic (M), samples is unknown. We described GPR30 and HER-2 expression in a collection of paired N/I/M samples, derived from the same individual.Materials and Methods: GPR30 and HER-2 expression was assessed by immunohistochemistry (IHC) in tissue microarrays, containing paraffin-embedded cores from 100 patients diagnosed with invasive BC. N and M samples were also available from the same patient. GPR30 expression was evaluated by an H-score (Intensity (0, negative; 1+, weak; 2+, moderate; 3+, strong) x Percentage of stained epithelial cells). HER-2 expression was evaluated per standard criteria. Log rank tests and Wald tests were employed to assess the clinical impact of these molecular targets on patient outcome based on Kaplan-Meier Product estimator and Cox Proportional Hazard Regression.Results: GPR30 was expressed in 50%, 76%, and 72% of N, I and M, respectively, samples. HER-2 (3+) was found in 14% and 18% of I and M samples, respectively. GPR30 expression in I cases correlated with expression in M cases, and HER-2 expression in I but not M cases. GPR30 expression in M cases correlated with expression in HER-2 expression in M cases. HER-2 expression in I cases correlated with expression in M samples (P&lt;0.05 for all comparisons). GPR30 and HER-2 expression were not associated with grade or stage (P&gt;0.05). GPR30 expression in I or M samples was not associated with either overall survival (OS) or BC-specific survival (BCSS)(P&gt;0.5). HER-2 expression was marginally associated with OS in I (P=0.06; Hazard Ratios (HR): 1.91; 95%CI: 0.956, 3.83) but not in M (P=0.23) cases. HER-2 was significantly associated with BCSS in I cases (P=0.03; HR: 2.39; 95%CI: 1.07, 5.32) and marginally in M (P=0.08) cases.Discussion: A previous study suggested that GPR30 expression predicted the development of metastasis. We found high GPR30 expression in both the primary and metastatic sample but the difference was not significant. While GPR30 expression was not associated with OS or BCSS, HER-2 expression was marginally associated with OS and significantly associated with BCSS in invasive cases.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 4158.

Apolipoprotein E/C1 locus variants modify renal cell carcinoma risk

Lipid peroxidation is considered a unifying mechanistic pathway through which known risk factors induce renal cell carcinoma (RCC). We hypothesized that genes selected a priori for their role in lipid peroxidation would modify cancer risk. We genotyped 635 single nucleotide polymorphisms (SNP) in 38candidate genes in 777 Caucasian RCC cases and 1,035 controls enrolled in a large European case-control study. Top candidate SNPs were confirmed among 718 Caucasian cases and 615 controls in a second study in the United States. Two of the three SNPs (rs8106822 and rs405509) that replicated in the U.S. study were within a regulatory region of the APOE promoter. The OR for rs8106822 A>G variant was 1.22(AG) and 1.41(GG) (P(trend) = 0.01) in the European study, 1.05(AG) and 1.51(GG) (P(trend) = 0.03) in the U.S. study, and 1.15(AG) and 1.44(GG) (P(trend) = 0.001) among 1,485 cases and 1,639 controls combined. The rs405509 G>T variant was associated with risk in the European (OR, 0.87(TG); OR, 0.71(TT); P(trend) = 0.02), the U.S. (OR, 0.68(TG); OR, 0.71(TT); P(trend) = 0.02), and both studies combined (OR(TG), 0.79; OR(TT), 0.71; P(trend) = 0.001), as was the G-G haplotype (r(2) = 0.64; P= 4.7 x 10(-4)). This association is biologically plausible as SNP rs405509 was shown to modify protein binding and transcriptional activity of the APOE protein in vitro and is in linkage disequilibrium with key known variants defining the e2, e3, and e4 alleles that modify risk of atherosclerosis, Alzheimer's disease risk, and progression to AIDS. In two large case-control studies, our findings further define a functional region of interest at the APOE locus that increases RCC susceptibility.

Abstract A89: Association of genes involved in lipid metabolism-peroxidation and risk of renal cancer in the Central European Renal Cancer Case-Control Study

A89

Recent descriptive studies have reported increases in kidney cancer incidence since the 1970s in the United States and globally. Lipid peroxidation has been suggested as a unifying mechanistic pathway by which several known risk factors including obesity, hypertension, and chemicals directly damage cells of the proximal renal tubules and induce renal carcinogenesis. This study investigated the association between renal cell cancer (RCC) risk and variation in genes that modify the effects of lipid peroxidation, inflammation, and oxidative stress. We conducted a case-control study of RCC (987 cases and 1298 controls) from Central and Eastern Europe and analyzed genomic DNA for 635 single nucleotide polymorphisms (SNPs) thirty-eight candidate genes using an Illumina Oligo Pool-All (OPA). First, the minimum p-value permutation test (MINP) was used to identify genes that remained significant with an FDR&lt;5%. Subsequently, a haplotype-based sliding window analysis of three consecutive SNPs was used to identify chromosome regions of interest that remained significant at a FDR&lt;5%. Six genes were selected for in-depth analysis after multiple testing correction of the single marker associations: APOE, GPX4, NOS2A and PTGS2. The overall gene-level p-values for these genes were 0.017, 0.020, 0.055 and 0.069 using the MINP test, respectively. The minimum FDR-adjusted p-values in a sliding window haplotype analysis were 0.0005, 0.0007, 0.0002 and 1.09x10-5, respectively. For these regions, age-, sex- and center-adjusted haplotype relative risks were computed using the HaploStats package in R. After adjustment, a strong signal centered around the promoter region of APOE gene (rs405509) remained significantly associated with decreased risk of RCC compared to persons homozygous for the referent haplotype (OR=0.73 95% CI:0.59-0.91); global p=0.001). A second haplotype window spanning from IVS7+11 to IVS12-52 of the NOS2A gene that was significantly associated with increased risk (OR=1.36 (95% CI:1.05-1.78); p-global p-0.006). Additional haplotype windows spanning the trans-membrane and tyrosine kinase domains of INSR (rs28601) and intron 2 of LEPR (rs970467) genes also were investigated further (FDR-adjusted p &lt;0.05). After adjustment in Haplostats, two additional high risk haplotypes were identified that were significantly associated with risk. To our knowledge this is the first and largest study of RCC conducted to evaluate these genes in relation to RCC. Although replication and fine mapping studies will be required to confirm these findings, this study supports the hypothesis variation in genes influencing lipid metabolism/peroxidation may increase susceptibility to sporadic kidney cancer.

Citation Information: Cancer Prev Res 2008;1(7 Suppl):A89.

[The value of an exploration of the mesogastric and epigastric regions in laparotomies (author's transl)]

The records of 4765 laparotmies including 1422 Caesarean sections were reviewed regarding additional surgical or medical findings. In 13.79% of the cases additional pathological findings were present which required additional general surgery or urologic surgery, or intra-operative or post-operative diagnostic steps. The exploration of the general abdominal cavity by inspection and/or palpation during the gynaecological or obstetric laparotomies was therefore very valuable. This simple preventive step requires very little time and maybe of considerable importance for the patient.