Two-sample survival probability curves: A graphical approach for the analysis of time to event data in clinical trials

With the aim to improve the communication of trial results, we introduce a novel graphical approach that complements the analysis of time to event outcomes in two-arm randomized trials. We define the so-called two-sample survival probability curve and propose a nonparametric estimator of the curve based on a random walk using Kaplan-Meier survival estimates for the two arms. We then use the estimated curve to visualize treatment effect as well as potential effect modification of factors of interest. We also propose to estimate two-sample survival probability curves within the framework of the Cox model to graphically assess model fit. The proposed two-sample survival probability plot puts trials in a standardized [0,1] × [0,1] space, allowing for a simple visualization of the main effect, effect modification, and the adequacy of a model fit.

Increasing sample diversity in psychiatric genetics - Introducing a new cohort of patients with schizophrenia and controls from Vietnam - Results from a pilot study

OBJECTIVES

Genome-Wide Association Studies (GWAS) of Schizophrenia (SCZ) have provided new biological insights; however, most cohorts are of European ancestry. As a result, derived polygenic risk scores (PRS) show decreased predictive power when applied to populations of different ancestries. We aimed to assess the feasibility of a large-scale data collection in Hanoi, Vietnam, contribute to international efforts to diversify ancestry in SCZ genetic research and examine the transferability of SCZ-PRS to individuals of Vietnamese Kinh ancestry.

METHODS

In a pilot study, 368 individuals (including 190 SCZ cases) were recruited at the Hanoi Medical University's associated psychiatric hospitals and outpatient facilities. Data collection included sociodemographic data, baseline clinical data, clinical interviews assessing symptom severity and genome-wide SNP genotyping. SCZ-PRS were generated using different training data sets: (i) European, (ii) East-Asian and (iii) trans-ancestry GWAS summary statistics from the latest SCZ GWAS meta-analysis.

RESULTS

SCZ-PRS significantly predicted case status in Vietnamese individuals using mixed-ancestry (R² liability = 4.9%, p = 6.83 × 10^-8), East-Asian (R² liability = 4.5%, p = 2.73 × 10^-7) and European (R² liability = 3.8%, p = 1.79 × 10^-6) discovery samples.

DISCUSSION

Our results corroborate previous findings of reduced PRS predictive power across populations, highlighting the importance of ancestral diversity in GWA studies.

A Bayesian hierarchical model for individual participant data meta-analysis of demand curves

Individual participant data meta-analysis is a frequently used method to combine and contrast data from multiple independent studies. Bayesian hierarchical models are increasingly used to appropriately take into account potential heterogeneity between studies. In this paper, we propose a Bayesian hierarchical model for individual participant data generated from the Cigarette Purchase Task (CPT). Data from the CPT details how demand for cigarettes varies as a function of price, which is usually described as an exponential demand curve. As opposed to the conventional random-effects meta-analysis methods, Bayesian hierarchical models are able to estimate both the study-specific and population-level parameters simultaneously without relying on the normality assumptions. We applied the proposed model to a meta-analysis with baseline CPT data from six studies and compared the results from the proposed model and a two-step conventional random-effects meta-analysis approach. We conducted extensive simulation studies to investigate the performance of the proposed approach and discussed the benefits of using the Bayesian hierarchical model for individual participant data meta-analysis of demand curves.

A mixed effects model for analyzing area under the curve of longitudinally measured biomarkers with missing data

A simple approach for analyzing longitudinally measured biomarkers is to calculate summary measures such as the area under the curve (AUC) for each individual and then compare the mean AUC between treatment groups using methods such as t test. This two-step approach is difficult to implement when there are missing data since the AUC cannot be directly calculated for individuals with missing measurements. Simple methods for dealing with missing data include the complete case analysis and imputation. A recent study showed that the estimated mean AUC difference between treatment groups based on the linear mixed model (LMM), rather than on individually calculated AUCs by simple imputation, has negligible bias under random missing assumptions and only small bias when missing is not at random. However, this model assumes the outcome to be normally distributed, which is often violated in biomarker data. In this paper, we propose to use a LMM on log-transformed biomarkers, based on which statistical inference for the ratio, rather than difference, of AUC between treatment groups is provided. The proposed method can not only handle the potential baseline imbalance in a randomized trail but also circumvent the estimation of the nuisance variance parameters in the log-normal model. The proposed model is applied to a recently completed large randomized trial studying the effect of nicotine reduction on biomarker exposure of smokers.

Longitudinal stability in cigarette smokers of urinary eicosanoid biomarkers of oxidative damage and inflammation

The urinary metabolites (Z)-7-[1R,2R,3R,5S)-3,5-dihydroxy-2-[(E,3S)-3-hydroxyoct-1-enyl]cyclopentyl]hept-5-enoic acid (8-iso-PGF2α), an F2-isoprostane and biomarker of oxidative damage, and "prostaglandin E2 metabolite" (PGE-M), a biomarker of inflammation, are elevated in cigarette smokers. However, there is little information in the literature on the longitudinal stability of these widely used biomarkers. In a large clinical trial involving 10 institutional sites, smokers were given, free of charge over a period of 20 weeks, Spectrum NRC600/601 research cigarettes containing 15.5 mg nicotine/g tobacco. All participants were instructed to smoke these cigarettes for the duration of the study. At weeks 4, 8, 12, 16, and 20, first morning urine voids were collected and analyzed for 8-iso-PGF2α and PGE-M using validated liquid chromatography-electrospray ionization-tandem mass spectrometry methods. The mean level of 8-iso-PGF2α at Week 4 was 1.34 ± 1.08 (S.D.) pmol/mg creatinine (N = 226) while that of PGE-M was 73.7 ± 113 (S.D.) pmol/mg creatinine (N = 232). The corresponding levels at Week 20 were 1.35 ± 0.93 (S.D.) pmol/mg creatinine (N = 209) for 8-iso-PGF2α and 74.2 ± 142 (S.D.) pmol/mg creatinine (N = 210) for PGE-M. There was variation in these values in the intervening weeks. The intra-class correlation coefficients (ICC) were 0.51 (95% CI, 0.45, 0.57) and 0.36 (0.30, 0.43), for 8-iso-PGF2α and PGE-M, respectively, indicating fair longitudinal stability for 8-iso-PGF2α and poorer longitudinal stability for PGE-M in cigarette smokers. Males had higher ICC values than females for both 8-iso-PGF2α and PGE-M. These results indicate that, in addition to cigarette smoking, endogenous processes of oxidative damage and inflammation influence the levels of these biomarkers over time among current smokers.

Longitudinal stability in cigarette smokers of urinary biomarkers of exposure to the toxicants acrylonitrile and acrolein

The urinary metabolites cyanoethyl mercapturic acid (CEMA) and 3-hydroxypropyl mercapturic acid (3-HPMA) have been widely used as biomarkers of exposure to acrylonitrile and acrolein, respectively, but there are no published data on their consistency over time in the urine of cigarette smokers. We provided, free of charge over a 20 week period, Spectrum NRC600/601 research cigarettes to cigarette smokers in the control arm of a randomized clinical trial of the reduced nicotine cigarette. Urine samples were collected at weeks 4, 8, 12, 16, and 20 and analyzed for CEMA and 3-HPMA, and total nicotine equivalents (TNE) using validated methods. Creatinine-corrected intra-class correlation coefficients for CEMA, 3-HPMA, and TNE were 0.67, 0.46, and 0.68, respectively, indicating good longitudinal consistency for CEMA, while that of 3-HPMA was fair. A strong correlation between CEMA and TNE values was observed. These data support the use of CEMA as a reliable biomarker of tobacco smoke exposure. This is the first report of the longitudinal stability of the biomarkers of acrylonitrile and acrolein exposure in smokers. The data indicate that CEMA, the biomarker of acrylonitrile exposure, is consistent over time in cigarette smokers, supporting its use. While 3-HPMA levels were less stable over time, this biomarker is nevertheless a useful monitor of human acrolein exposure because of its specificity to this toxicant.

Analysis of self-report and biochemically verified tobacco abstinence outcomes with missing data: a sensitivity analysis using two-stage imputation

Background

Missing data are common in tobacco studies. It is well known that from the observed data alone, it is impossible to distinguish between missing mechanisms such as missing at random (MAR) and missing not at random (MNAR). In this paper, we propose a sensitivity analysis method to accommodate different missing mechanisms in cessation outcomes determined by self-report and urine validation results.

Methods

We propose a two-stage imputation procedure, allowing survey and urine data to be missing under different mechanisms. The motivating data were from a tobacco cessation trial examining the effects of the extended vs. standard Quit and Win contests and counseling vs. no counseling under a 2-by-2 factorial design. The primary outcome was 6-month biochemically verified tobacco abstinence.

Results

Our proposed method covers a wide spectrum of missing scenarios, including the widely adopted “missing = smoking” imputation by assuming a perfect smoking-missing correlation (an extreme case of MNAR), the MAR case by assuming a zero smoking-missing correlation, and many more in between. The analysis of the data example shows that the estimated effects of the studied interventions are sensitive to the different missing assumptions on the survey and urine data.

Conclusions

Sensitivity analysis has played a crucial role in assessing the robustness of the findings in clinical trials with missing data. The proposed method provides an effective tool for analyzing missing data introduced at two different stages of outcome assessment, the self-report and validation time. Our methods are applicable to trials studying biochemically verified abstinence from alcohol and other substances.

Electronic supplementary material

The online version of this article (10.1186/s12874-018-0635-2) contains supplementary material, which is available to authorized users.

Effect of Immediate vs Gradual Reduction in Nicotine Content of Cigarettes on Biomarkers of Smoke Exposure: A Randomized Clinical Trial

Importance

The optimal temporal approach for reducing nicotine to minimally or nonaddictive levels in all cigarettes sold in the United States has not been determined.

Objectives

To determine the effects of immediate vs gradual reduction in nicotine content to very low levels and as compared with usual nicotine level cigarettes on biomarkers of toxicant exposure.

Design, Setting, and Participants

A double-blind, randomized, parallel-design study with 2 weeks of baseline smoking and 20 weeks of intervention was conducted at 10 US sites. A volunteer sample of daily smokers with no intention to quit within 30 days was recruited between July 2014 and September 2016, with the last follow-up completed in March 2017.

Interventions

(1) Immediate reduction to 0.4 mg of nicotine per gram of tobacco cigarettes; (2) gradual reduction from 15.5 mg to 0.4 mg of nicotine per gram of tobacco cigarettes with 5 monthly dose changes; or (3) maintenance on 15.5 mg of nicotine per gram of tobacco cigarettes.

Main Outcomes and Measures

Between-group differences in 3 co-primary biomarkers of smoke toxicant exposure: breath carbon monoxide (CO), urine 3-hydroxypropylmercapturic acid (3-HPMA, metabolite of acrolein), and urine phenanthrene tetraol (PheT, indicator of polycyclic aromatic hydrocarbons) calculated as area under the concentration-time curve over the 20 weeks of intervention.

Results

Among 1250 randomized participants (mean age, 45 years; 549 women [44%]; 958 [77%] completed the trial), significantly lower levels of exposure were observed in the immediate vs gradual reduction group for CO (mean difference, -4.06 parts per million [ppm] [95% CI, -4.89 to -3.23]; P < .0055), 3-HPMA (ratio of geometric means, 0.83 [95% CI, 0.77 to 0.88]; P < .0055), and PheT (ratio of geometric means, 0.88 [95% CI, 0.83 to 0.93]; P < .0055). Significantly lower levels of exposure were observed in the immediate reduction vs control group for CO (mean difference, -3.38 [95% CI, -4.40 to -2.36]; P < .0055), 3-HPMA (ratio of geometric means, 0.81 [95% CI, 0.75 to 0.88]; P < .0055), and PheT (ratio of geometric means, 0.86 [95% CI, 0.81 to 0.92]; P < .0055). No significant differences were observed between the gradual reduction vs control groups for CO (mean difference, 0.68 [95% CI, -0.31 to 1.67]; P = .18), 3-HPMA (ratio of geometric means, 0.98 [95% CI, 0.91 to 1.06]; P = .64), and PheT (ratio of geometric means, 0.98 [95% CI, 0.92 to 1.04]; P = .52).

Conclusions and Relevance

Among smokers, immediate reduction of nicotine in cigarettes led to significantly greater decreases in biomarkers of smoke exposure across time compared with gradual reduction or a control group, with no significant differences between gradual reduction and control.

Trial Registration

clinicaltrials.gov Identifier: NCT02139930.

Presence of the Carcinogen N'-Nitrosonornicotine in Saliva of E-cigarette Users

Many harmful constituents are present in e-cigarettes at much lower levels than in cigarette smoke, and the results of analysis of urinary biomarkers in e-cigarette users are consistent with these findings. However, understanding the health effects of chronic exposures to e-cigarette aerosols may require thinking beyond these comparisons. In this study, we investigated the endogenous formation of the tobacco-specific oral and esophageal carcinogen N'-nitrosonornicotine (NNN) in e-cigarette users. Salivary NNN, nornicotine, and nicotine as well as urinary tobacco biomarkers, including total NNN, were analyzed in 20 e-cigarette users, 20 smokers, and 19 nonsmokers. Nornicotine and NNN levels in e-cigarettes used by the study participants were also analyzed. The mean of NNN in saliva of e-cigarette users was 14.6 (±23.1) pg/mL, ranging from nonquantifiable (below the limit of quantitation, LOQ) to 76.0 pg/mL. In smokers, salivary NNN ranged from below LOQ to 739 pg/mL, with 80% of smokers having salivary NNN in the range of levels found in e-cigarette users. Consistent with a previous report, very low levels of urinary total NNN were present in only 5 out of 20 e-cigarette users (ranging from 0.001 to 0.01 pmol/mL urine). Only trace levels of NNN were found in e-cigarette liquids. Together, our findings demonstrate that NNN is formed endogenously in e-cigarette users. While the overall exposure to NNN in e-cigarette users is dramatically lower than in smokers, the known carcinogenic potency of NNN warrants further investigations into the potential consequences of its endogenous formation. Salivary NNN, rather than urinary total NNN, which accounts for only 1-3% of the NNN dose, should be used to monitor e-cigarette users' exposure to this carcinogen.

A Bayesian hierarchical model for demand curve analysis

Drug self-administration experiments are a frequently used approach to assess the abuse liability and reinforcing property of a compound. It has been used to assess the abuse liabilities of various substances such as psychomotor stimulants and hallucinogens, food, nicotine, and alcohol. The demand curve generated from a self-administration study describes how demand of a drug or non-drug reinforcer varies as a function of price. With the approval of the 2009 Family Smoking Prevention and Tobacco Control Act, demand curve analysis provides crucial evidence to inform the US Food and Drug Administration's policy on tobacco regulation because it produces several important quantitative measurements to assess the reinforcing strength of nicotine. The conventional approach popularly used to analyze the demand curve data is individual-specific non-linear least square regression. The non-linear least square approach sets out to minimize the residual sum of squares for each subject in the dataset; however, this one-subject-at-a-time approach does not allow for the estimation of between- and within-subject variability in a unified model framework. In this paper, we review the existing approaches to analyze the demand curve data, non-linear least square regression, and the mixed effects regression and propose a new Bayesian hierarchical model. We conduct simulation analyses to compare the performance of these three approaches and illustrate the proposed approaches in a case study of nicotine self-administration in rats. We present simulation results and discuss the benefits of using the proposed approaches.

A Bayesian hierarchical model for demand curve analysis

Drug self-administration experiments are a frequently used approach to assessing the abuse liability and reinforcing property of a compound. It has been used to assess the abuse liabilities of various substances such as psychomotor stimulants and hallucinogens, food, nicotine, and alcohol. The demand curve generated from a self-administration study describes how demand of a drug or non-drug reinforcer varies as a function of price. With the approval of the 2009 Family Smoking Prevention and Tobacco Control Act, demand curve analysis provides crucial evidence to inform the US Food and Drug Administration's policy on tobacco regulation, because it produces several important quantitative measurements to assess the reinforcing strength of nicotine. The conventional approach popularly used to analyze the demand curve data is individual-specific non-linear least square regression. The non-linear least square approach sets out to minimize the residual sum of squares for each subject in the dataset; however, this one-subject-at-a-time approach does not allow for the estimation of between- and within-subject variability in a unified model framework. In this paper, we review the existing approaches to analyze the demand curve data, non-linear least square regression, and the mixed effects regression and propose a new Bayesian hierarchical model. We conduct simulation analyses to compare the performance of these three approaches and illustrate the proposed approaches in a case study of nicotine self-administration in rats. We present simulation results and discuss the benefits of using the proposed approaches.

A two-part mixed effects model for cigarette purchase task data

The Cigarette Purchase Task is a behavioral economic assessment tool designed to measure the relative reinforcing efficacy of cigarette smoking across different prices. An exponential demand equation has become a standard model for analyzing purchase task data, but its utility is compromised by its inability to accommodate values of zero consumption. We propose a two-part mixed effects model that keeps the same exponential demand equation for modeling nonzero consumption values, while providing a logistic regression for the binary outcome of zero versus nonzero consumption. Therefore, the proposed model can accommodate zero consumption values and retain the features of the exponential demand equation at the same time. As a byproduct, the logistic regression component of the proposed model provides a new demand index, the "derived breakpoint", for the price above which a subject is more likely to be abstinent than to be smoking. We apply the proposed model to data collected at baseline from college students (N = 1,217) enrolled in a randomized clinical trial utilizing financial incentives to motivate tobacco cessation. Monte Carlo simulations showed that the proposed model provides better fits than an existing model. We note that the proposed methodology is applicable to other purchase task data, for example, drugs of abuse.

A Randomized Controlled Trial of Green Tea Extract Supplementation and Mammographic Density in Postmenopausal Women at Increased Risk of Breast Cancer

Epidemiologic and animal studies suggest a protective role of green tea against breast cancer. However, the underlying mechanism is not understood. We conducted a randomized, double-blinded, placebo-controlled phase II clinical trial to investigate whether supplementation with green tea extract (GTE) modifies mammographic density (MD), as a potential mechanism, involving 1,075 healthy postmenopausal women. Women assigned to the treatment arm consumed daily 4 decaffeinated GTE capsules containing 1,315 mg total catechins, including 843 mg epigallocatechin-3-gallate (EGCG) for 12 months. A computer-assisted method (Madena) was used to assess MD in digital mammograms at baseline and month 12 time points in 932 completers (462 in GTE and 470 in placebo). GTE supplementation for 12 months did not significantly change percent MD (PMD) or absolute MD in all women. In younger women (50-55 years), GTE supplementation significantly reduced PMD by 4.40% as compared with the placebo with a 1.02% PMD increase from pre- to postintervention (P = 0.05), but had no effect in older women (Pinteraction = 0.07). GTE supplementation did not induce MD change in other subgroups of women stratified by catechol-O-methyltransferase genotype or level of body mass index. In conclusion, 1-year supplementation with a high dose of EGCG did not have a significant effect on MD measures in all women, but reduced PMD in younger women, an age-dependent effect similar to those of tamoxifen. Further investigation of the potential chemopreventive effect of green tea intake on breast cancer risk in younger women is warranted. Cancer Prev Res; 10(12); 710-8. ©2017 AACR.

Impact of smoking reduced nicotine content cigarettes on sensitivity to cigarette price: further results from a multi-site clinical trial

AIMS

To assess the impact of a reduction in the nicotine content of cigarettes on estimated consumption of reduced nicotine cigarettes and usual brand cigarettes at a variety of hypothetical prices.

DESIGN

Double-blind study with participants assigned randomly to receive cigarettes for 6 weeks that were either usual brand or an investigational cigarette with one of five nicotine contents.

SETTING

Ten sites across the United States.

PARTICIPANTS

A total of 839 eligible adult smokers randomized from 2013 to 2014.

INTERVENTION AND COMPARATOR

Participants received their usual brand or an investigational cigarette with one of five nicotine contents: 15.8 (primary control), 5.2, 2.4, 1.3, or 0.4 mg/g.

MEASUREMENTS

The Cigarette Purchase Task was completed at baseline and at the week 6 post-randomization visit.

FINDINGS

Compared with normal nicotine content controls, the lowest nicotine content (0.4 mg/g) reduced the number of study cigarettes participants estimated they would smoke at a range of prices [mean reduction relative to 15.8 mg/g at a price of $4.00/pack: 9.50, 95% confidence interval (CI) = 6.81,12.19]. The lowest nicotine content also reduced the maximum amount of money allocated to study cigarettes and the price at which participants reported they would stop buying study cigarettes [median reduction relative to 15.8 mg/g, 95% CI = $8.21 (4.27,12.15) per day and $0.44 (0.17,0.71) per cigarette, respectively]. A reduction in nicotine content to the lowest level also reduced the maximum amount of money allocated to usual brand cigarettes (median reduction relative to 15.8 mg/g: $4.39 per day, 95% CI = 1.88,6.90).

CONCLUSIONS

In current smokers, a reduction in nicotine content may reduce cigarette consumption, reduce the reinforcement value of cigarettes and increase cessation if reduced nicotine content cigarettes were the only cigarette available for purchase.

Randomized Trial of Reduced-Nicotine Standards for Cigarettes

BACKGROUND

The Food and Drug Administration can set standards that reduce the nicotine content of cigarettes.

METHODS

We conducted a double-blind, parallel, randomized clinical trial between June 2013 and July 2014 at 10 sites. Eligibility criteria included an age of 18 years or older, smoking of five or more cigarettes per day, and no current interest in quitting smoking. Participants were randomly assigned to smoke for 6 weeks either their usual brand of cigarettes or one of six types of investigational cigarettes, provided free. The investigational cigarettes had nicotine content ranging from 15.8 mg per gram of tobacco (typical of commercial brands) to 0.4 mg per gram. The primary outcome was the number of cigarettes smoked per day during week 6.

RESULTS

A total of 840 participants underwent randomization, and 780 completed the 6-week study. During week 6, the average number of cigarettes smoked per day was lower for participants randomly assigned to cigarettes containing 2.4, 1.3, or 0.4 mg of nicotine per gram of tobacco (16.5, 16.3, and 14.9 cigarettes, respectively) than for participants randomly assigned to their usual brand or to cigarettes containing 15.8 mg per gram (22.2 and 21.3 cigarettes, respectively; P<0.001). Participants assigned to cigarettes with 5.2 mg per gram smoked an average of 20.8 cigarettes per day, which did not differ significantly from the average number among those who smoked control cigarettes. Cigarettes with lower nicotine content, as compared with control cigarettes, reduced exposure to and dependence on nicotine, as well as craving during abstinence from smoking, without significantly increasing the expired carbon monoxide level or total puff volume, suggesting minimal compensation. Adverse events were generally mild and similar among groups.

CONCLUSIONS

In this 6-week study, reduced-nicotine cigarettes versus standard-nicotine cigarettes reduced nicotine exposure and dependence and the number of cigarettes smoked. (Funded by the National Institute on Drug Abuse and the Food and Drug Administration Center for Tobacco Products; ClinicalTrials.gov number, NCT01681875.).

Carcinogenicity and DNA adduct formation of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone and enantiomers of its metabolite 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol in F-344 rats

4-(Methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) is metabolized to enantiomers of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL), found in the urine of virtually all people exposed to tobacco products. We assessed the carcinogenicity in male F-344 rats of (R)-NNAL (5 ppm in drinking water), (S)-NNAL (5 ppm), NNK (5 ppm) and racemic NNAL (10 ppm) and analyzed DNA adduct formation in lung and pancreas of these rats after 10, 30, 50 and 70 weeks of treatment. All test compounds induced a high incidence of lung tumors, both adenomas and carcinomas. NNK and racemic NNAL were most potent; (R)-NNAL and (S)-NNAL had equivalent activity. Metastasis was observed from primary pulmonary carcinomas to the pancreas, particularly in the racemic NNAL group. DNA adducts analyzed were O (2)-[4-(3-pyridyl)-4-oxobut-1-yl]thymidine (O (2)-POB-dThd), 7-[4-(3-pyridyl)-4-oxobut-1-yl]guanine(7-POB-Gua),O (6)-[4-(3-pyridyl)-4-oxobut-1-yl]deoxyguanosine(O (6)-POB-dGuo),the 4-(3-pyridyl)-4-hydroxybut-1-yl(PHB)adductsO (2)-PHB-dThd and 7-PHB-Gua, O (6)-methylguanine (O (6)-Me-Gua) and 4-hydroxy-1-(3-pyridyl)-1-butanone (HPB)-releasing adducts. Adduct levels significantly decreased with time in the lungs of rats treated with NNK. Pulmonary POB-DNA adducts and O (6)-Me-Gua were similar in rats treated with NNK and (S)-NNAL; both were significantly greater than in the (R)-NNAL rats. In contrast, pulmonary PHB-DNA adduct levels were greatest in the rats treated with (R)-NNAL. Total pulmonary DNA adduct levels were similar in (S)-NNAL and (R)-NNAL rats. Similar trends were observed for DNA adducts in the pancreas, but adduct levels were significantly lower than in the lung. The results of this study clearly demonstrate the potent pulmonary carcinogenicity of both enantiomers of NNAL in rats and provide important new information regarding DNA damage by these compounds in lung and pancreas.

Effect of cigarette smoking on urinary 2-hydroxypropylmercapturic acid, a metabolite of propylene oxide

2-Hydroxypropylmercapturic acid (2-HPMA) is a urinary biomarker of exposure to propylene oxide, a mutagen and carcinogen to which humans are exposed through inhalation of cigarette smoke as well as in certain environmental and occupational settings. 2-HPMA is the final product of a detoxification pathway in which propylene oxide is conjugated with glutathione, and the resulting conjugate is further metabolized and excreted. We have developed and validated a liquid chromatography-atmospheric pressure chemical ionization-tandem mass spectrometric (LC-APCI-MS/MS) method for the rapid quantitation of 2-HPMA in human urine. The method was applied to an analysis of urine samples from 40 smokers and 40 nonsmokers as well as from a group of 15 subjects who quit smoking. The results demonstrate that smokers have significantly (P<0.001) higher levels of urinary 2-HPMA (median=480pmol/mg creatinine) than do nonsmokers (208pmol/mg). Similarly, subjects who quit smoking for four weeks exhibited a significant (P<0.001) 52% median decrease in urinary 2-HPMA upon cessation. Approximately 5% of all urine samples had unusually high levels of 2-HPMA (>10 times higher than the median), apparently unrelated to tobacco smoke exposure or available demographic data. The method presented here can be used to rapidly quantify an individual's exposure to propylene oxide via tobacco smoke or other sources.

Abstract A01: Lung and pancreatic carcinogenicity and DNA binding of the enantiomers of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) in F344 rats

The tobacco-specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) is a potent pulmonary carcinogen in laboratory animals and is believed to play an important role as a cause of tobacco related cancers. NNK is metabolically converted to NNAL in virtually all biological systems. All tobacco users as well as people exposed to secondhand tobacco smoke have NNAL in their urine. NNAL has a chiral center at its 1-position, thus consequently exists in enantiomeric forms. Previous studies have shown differing amounts of (R)- or (S)-NNAL in human tissues and urine after exposure to NNK, depending on the conditions and the system studied. However, little is known about the carcinogenic activity of (R)- or (S)-NNAL. Only one previous study has been reported demonstrating higher lung tumorigenicity of (S)-NNAL than (R)-NNAL in an A/J mouse model. Understanding mechanisms of carcinogenesis by these compounds can provide critical insights relevant for cancer prevention in people exposed to tobacco products. Therefore, in the study reported here, we have evaluated the carcinogenicity and DNA binding of the NNAL enantiomers in F-344 rats chronically treated with these compounds in the drinking water.

Groups of 24 male F-344 rats, 7 weeks of age, were treated chronically with NNK, (R)-NNAL or (S)-NNAL (5 ppm in drinking water). Controls received tap water or racemic NNAL (15 rats, 10 ppm in drinking water). The chronic treatment lasted 90 weeks. The number of animals per group which came to necropsy at the end of the study were: NNK, 23; (R)-NNAL, 23; (S)-NNAL, 22; control, 22; racemic NNAL, 15. Nearly all animals in the (R)-NNAL, (S)-NNAL, racemic NNAL, and NNK-treated groups had lung tumors. In the (R)-NNAL-treated group, there were 22 animals with lung adenoma and 3 with lung carcinoma while in the (S)-NNAL group there were 20 rats with lung adenoma and 5 with lung carcinoma. In the racemic NNAL group there were 15 rats with lung adenoma and 13 with lung carcinoma while in the NNK group there were 23 rats with lung adenoma and 14 with lung carcinoma. There were no lung tumors in the control animals. These results demonstrate that both enantiomers of NNAL are pulmonary carcinogens in the F-344 rat, but less carcinogenic to the lung than NNK (P&lt;0.001). Tumors of the pancreas, predominantly exocrine adenocarcinomas, were also observed in this study: (R)-NNAL, 1 rat with 2 tumors; (S)-NNAL 2 rats with 3 tumors; racemic NNAL, 4 rats with 14 tumors; NNK 3 rats with 3 tumors.

DNA binding studies were performed using tissues harvested at various time-points throughout the experiment. Rats (9 per group) from the NNK, (R)-NNAL, (S)-NNAL, and control groups were euthanized at 10, 30, 50 and 70 weeks. DNA was isolated from the lung and pancreas tissues. The DNA samples were analyzed by LC-ESI-MS/MS with selected reaction monitoring (SRM) analysis for various DNA adducts. O6-Methyl-Gua, POB-DNA adducts, including 7-POB-Gua, O2-POB-dThd and O6-POB-dG and PHB-DNA adducts, including 7-PHB-Gua, O2-PHB-dThd and O6-PHB-dG were measured in lung DNA samples. POB-DNA adducts were measured in pancreas DNA. The preliminary results from these analyses indicate that O6-Methyl-Gua and POB-DNA adducts levels (both in lung and pancreas DNA) were similar in NNK and (S)-NNAL treated rats and significantly higher than in (R)-NNAL treated rats, while PHB-DNA adducts levels were significantly higher in (R)-NNAL treated animals compared to NNK and (S)-NNAL treated groups. The results of this study demonstrate that both (R)-NNAL and (S)-NNAL, at 5 ppm in the drinking water, are effective pulmonary carcinogens in the F-344 rat and are metabolically activated to DNA binding metabolites in the lung. Furthermore, the results presented here confirm the previously observed pancreatic carcinogenicity of racemic NNAL in the F-344 rat. Collectively, these results provide important new insights relevant to mechanisms of carcinogenesis by NNK and NNAL, and to lung and pancreatic cancer in people exposed to tobacco products.

Citation Format: Silvia Balbo, Charles S. Johnson, Lijiao Zhao, M Gerard O'Sullivan, Irina Stepanov, Mingyao Wang, Fekadu Kassie, Steven Carmella, Pramod Upadhyaya, Chap T. Le, Stephen S. Hecht. Lung and pancreatic carcinogenicity and DNA binding of the enantiomers of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) in F344 rats. [abstract]. In: Proceedings of the Twelfth Annual AACR International Conference on Frontiers in Cancer Prevention Research; 2013 Oct 27-30; National Harbor, MD. Philadelphia (PA): AACR; Can Prev Res 2013;6(11 Suppl): Abstract nr A01.

Analysis of cigarette purchase task instrument data with a left-censored mixed effects model

The drug purchase task is a frequently used instrument for measuring the relative reinforcing efficacy (RRE) of a substance, a central concept in psychopharmacological research. Although a purchase task instrument, such as the cigarette purchase task (CPT), provides a comprehensive and inexpensive way to assess various aspects of a drug's RRE, the application of conventional statistical methods to data generated from such an instrument may not be adequate by simply ignoring or replacing the extra zeros or missing values in the data with arbitrary small consumption values, for example, 0.001. We applied the left-censored mixed effects model to CPT data from a smoking cessation study of college students and demonstrated its superiority over the existing methods with simulation studies. Theoretical implications of the findings, limitations of the proposed method, and future directions of research are also discussed.

Analysis of 4-hydroxy-1-(3-pyridyl)-1-butanone (HPB)-releasing DNA adducts in human exfoliated oral mucosa cells by liquid chromatography-electrospray ionization-tandem mass spectrometry

Quantitation of DNA adducts could provide critical information on the relationship between exposure to tobacco smoke and cancer risk in smokers. In this study, we developed a robust and sensitive liquid chromatography-tandem mass spectrometry method for the analysis of 4-hydroxy-1-(3-pyridyl)-1-butanone (HPB)-releasing DNA adducts in human oral cells, a noninvasive source of DNA for biomarker studies. Isolated DNA undergoes acid hydrolysis, after which samples are purified by solid-phase extraction and analyzed by LC-ESI-MS/MS. The developed method was applied to the analysis of samples obtained via collection with a commercial mouthwash from 30 smokers and 15 nonsmokers. In smokers, the levels of HPB-releasing DNA adducts averaged 12.0 pmol HPB/mg DNA (detected in 20 out of 28 samples with quantifiable DNA yield), and in nonsmokers, the levels of adducts averaged 0.23 pmol/mg DNA (detected in 3 out of 15 samples). For the 30 smoking subjects, matching buccal brushings were also analyzed, and HPB-releasing DNA adducts were detected in 24 out of 27 samples with quantifiable DNA yield, averaging 44.7 pmol HPB/mg DNA. The levels of adducts in buccal brushings correlated with those in mouthwash samples of smokers (R = 0.73, p < 0.0001). Potentially, the method can be applied in studies of individual susceptibility to tobacco-induced cancers in humans.

Abstract A69: Pilot study of the effects of indole-3-carbinol on deuterated phenanthrene metabolism in smokers

Background/Purpose: Polycyclic aromatic hydrocarbons (PAH), widely considered as critical causative agents of tobacco-related lung cancer, are found in high levels in tobacco smoke and require metabolic activation to exert their carcinogenic effects. The development of urinary biomarkers of PAH metabolism using the more abundant and generally non-carcinogenic phenanthrene (Phe) as a surrogate of the prototypic carcinogenic PAH benzo[a]pyrene (BaP) has provided a reliable tool to characterize the uptake and metabolism of BaP in smokers. There is wide inter-individual variation in PheT metabolism. Furthermore, smokers who are more efficient metabolic activators of Phe appear to have a higher risk of developing lung cancer in prospective case-control studies. We examined the effects of indole-3-carbinol (I3C), a compound arising from cruciferous vegetables shown to possess anti-cancer activity, in modifying Phe metabolism. We hypothesized that I3C might have a chemopreventive effect in cigarette smokers by abrogating the metabolic activation and/or detoxification of [D10]Phe.

Procedures: Ten micrograms of [D10]Phe was administered via inhalation of a smoked cigarette prior to and after 7 days if I3C 400 mg po BID. Plasma and urine samples were collected at baseline and for 48 hours following [D10]Phe administration. Deuterated phenanthrene tetraol ([D10]PheT, a reflection of uptake and metabolic activation via the diol epoxide pathway), and deuterated phenanthrol ([D10]HOPhe, a reflection of detoxification and elimination) were quantified in urine and plasma before and after I3C and compared.

Results: A total of 8 subjects completed the study procedures, 6 females and 2 males. Subject 8 was clearly an outlier and was excluded from analysis. One-sample t-test was used to compare the mean difference in [D10]PheT and the mean difference in [D10]HOPhe among the group before and after I3C. The reduction in [D10]PheT in urine was significant (one-sample t-test, p=.023), although only marginally so in plasma (=.083). [D10]PheT AUC was not reduced (p=.23). [D10]HOPhe was generally reduced but not significantly (p=.15). Correlation between 6-hour and 48-hour [D10]PheT and [D10]HOPhe was very strong (r=.873; p=.010 and r=.968;p&lt;.001, respectively).

Conclusion: I3C may be an effective chemopreventive agent in tobacco-related lung cancer by reducing the metabolic activation of carcinogenic PAH. A larger, definitive study is needed to confirm these results.

Citation Format: Naomi Fujioka, Yan Zhong, J. Bradley Holchalter, Diane Rauch, Joni J. Jensen, Chap T. Le, Dorothy K. Hatsukami, Stephen S. Hecht. Pilot study of the effects of indole-3-carbinol on deuterated phenanthrene metabolism in smokers. [abstract]. In: Proceedings of the Eleventh Annual AACR International Conference on Frontiers in Cancer Prevention Research; 2012 Oct 16-19; Anaheim, CA. Philadelphia (PA): AACR; Cancer Prev Res 2012;5(11 Suppl):Abstract nr A69.

Cap-dependent translation blockade and fixed dose-rate gemcitabine: interaction in an in vitro bioreactor system

Translation initiation commences with the binding of eIF-4F to the mRNA 5'-end cap. eIF-4F binds the cap structure via its eIF-4E subunit, which is the rate-limiting step for the initiation of translation. This pathway can be inhibited by 4E-binding proteins (4E-BPs). The present study investigated prolonged gemcitabine infusion in combination with reduced eIF-4E function on NSCLC cell viability in an in vitro bioreactor system. To assess attachment to the hollow fibers, cells with dominant active 4E-BP1 were first analyzed by scanning electron microscopy. Cells were treated with 0.5- or 2.5h (fixed dose rate) infusion (same total dose), simulating human plasma gemcitabine concentration-time profiles. An interaction was observed between fixed dose rate infusion gemcitabine and presence of dominant active 4E-BP1. We conclude that cap-dependent translation blockade and fixed dose rate infusion gemcitabine treatment results in a significant interaction affecting cell viability in vitro.

A prospectively measured serum biomarker for a tobacco-specific carcinogen and lung cancer in smokers

BACKGROUND

No prior studies have related a tobacco-specific carcinogen to the risk of lung cancer in smokers. Of the over 60 known carcinogens in cigarette smoke, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) is specific to tobacco and causes lung cancer in laboratory animals. Its metabolites, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol and its glucuronides (total NNAL), have been studied as biomarkers of exposure to NNK. We studied the relation of prospectively measured NNK biomarkers to lung cancer risk.

METHODS

In a case-control study nested in the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial, we randomly selected 100 lung cancer cases and 100 controls who smoked at baseline and analyzed their baseline serum for total NNAL, cotinine, and r-1,t-2,3,c-4-tetrahydroxy-1,2,3,4-tetrahydrophenanthrene (PheT), a biomarker of polycyclic aromatic hydrocarbon exposure and metabolic activation. To examine the association of the biomarkers with all lung cancers and for histologic subtypes, we computed odds ratios for total NNAL, PheT, and cotinine using logistic regression to adjust for potential confounders.

FINDINGS

Individual associations of age, smoking duration, and total NNAL with lung cancer risk were statistically significant. After adjustment, total NNAL was the only biomarker significantly associated with risk (odds ratio, 1.57 per unit SD increase; 95% confidence interval, 1.08-2.28). A similar statistically significant result was obtained for adenocarcinoma risk, but not for nonadenocarcinoma.

CONCLUSIONS

This first reporting of the effect of the prospectively measured tobacco-specific biomarker total NNAL, on risk of lung cancer in smokers provides insight into the etiology of smoking-related lung cancer and reinforces targeting NNK for cancer prevention.

Smoking reduction fails to improve clinical and biological markers of cardiac disease: a randomized controlled trial

Cigarette reduction has been proposed as a treatment goal for smokers who are not interested in stopping completely. This randomized controlled trial was designed to determine the effect of a smoking reduction intervention on smoking behavior, symptoms of heart disease, and biomarkers of tobacco exposure. It included 152 patients with heart disease who did not intend to stop smoking in the next 30 days. Participants were randomly assigned to smoking reduction (SR) or usual care (UC). SR subjects received counseling and nicotine replacement therapy to encourage > or =50% reduction in cigarettes per day (CPD). They were followed at 1, 3, 6, 12 and 18 months to assess smoking, heart disease symptoms, quality of life and nicotine, cotinine, carbon monoxide (CO), white blood cell (WBC) count, fibrinogen, hs-C-reactive protein (hs-CRP), F2-isoprostane, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol and its glucuronides (total NNAL), and 1-hydroxypyrene (1-HOP). At 6 months SR participants reduced by 10.9 CPD, compared with 7.4 CPD in UC (difference NS). At 18 months, 9/78 SR vs. 9/74 UC participants quit smoking. There were no significant differences between treatment groups in angina, quality of life or adverse events, nicotine, cotinine, CO, WBC count, fibrinogen, hs-CRP, F2-isoprostane, total NNAL or 1-HOP levels at any time point. To determine if smoking reduction, regardless of treatment condition, was associated with improved outcomes, we compared all subjects at 6 months to baseline (mean reduction in CPD from 27.4 to 18.1, p<.01). There were no significant changes in outcome variables except CO, which decreased by 5.5 ppm (p<.01). There were also no significant improvements considering only subjects who reduced by > or =50%, or those who had no history of reduction prior to enrollment in the study. The SR intervention did not significantly reduce CPD or toxin exposure, or improve smoking cessation or clinical outcomes compared to UC. These results emphasize the importance of abstinence for smokers with heart disease to minimize health risks from tobacco.

Efficacy of an osmotic pump delivered, GM-CSF-based tumor vaccine in the treatment of upper aerodigestive squamous cell carcinoma in rats

PURPOSE

Upper aerodigestive tract (UADT) cancer has not experienced significant overall survival improvement for over 20 years, and no successful treatments for systemic disease exist. Most patients with UADT cancer experience immune suppression, therefore immune restorative therapies may offer promise for these patients. We presently tested the efficacy of granulocyte macrophage-colony stimulating factor (GM-CSF) delivered via 28-day continuous infusion pump, in combination with irradiated tumor cells, in a flank model of UADT cancer.

METHODS

Five groups of rats were inoculated with syngeneic mucosally derived squamous carcinoma cells (FAT-7). Osmotic minipumps were implanted in the contralateral flank to deliver GM-CSF at 0 (PBS), 0.1, 1, 10, or 100 ng/day (n = 6 per group) for 28 days; 10(6) irradiated FAT-7 cells (ITC) were injected at the site of the GM-CSF infusion on days 0, 3, 7, 14, and 21 immune infiltrates in tumors were analyzed.

RESULTS

Rats that received 10 or 100 ng/day GM-CSF/ITC had a significantly slower tumor growth rate compared to those who received 0, 0.1, or 1 ng/day (ANOVA, P < 0.01). There were increased CD 4+, CD 8+, and CD 68+ cells in tumors of GM-CSF/ITC treated animals over controls.

CONCLUSION

GM-CSF (10 or 100 ng/day) delivered locally via osmotic pump with ITC slows the growth rate of mucosally derived squamous cell carcinoma in rats while improving immune cell infiltrates. The efficacy of locally delivered GM-CSF immunotherapy in this model may be a first step toward this immunotherapy strategy for humans.

Short versus continuous gemcitabine treatment of non-small cell lung cancer in an in vitro cell culture bioreactor system

Five-year survival for non-small cell lung cancer is 15%. Gemcitabine is a nucleoside analogue that inhibits ribonucleotide reductase and interferes with DNA replication. In this study, we sought to compare short versus continuous infusion gemcitabine in an in vitro bioreactor system using pharmacokinetic-guided dosing. Gemcitabine was infused over either 0.5 or 2.5h to produce concentration-time profiles that mimic those measured in biological samples (i.e., patient plasma). The effects of gemcitabine on the growth and survival of H2009 cells were examined using trypan blue staining, cell cycle analysis, TUNEL assay, and clonogenic assay. Data were analyzed with two ways analysis of variance. Maximum gemcitabine (Cmax) concentrations during the short infusion were 51.2+/-10.4 microM and for the continuous, 14.8+/-2.93 microM. Steady-state concentrations during the continuous infusions were 14.9+/-2.90 microM. Gemcitabine treatment resulted in a decrease for G1 fraction relative to controls. G2/M, subG1 and TUNEL were higher following gemcitabine relative to controls. Survival was approximately 20-fold higher following the short infusion compared with the continuous infusion (p = 0.0085). In conclusion, gemcitabine infused by this novel method induced apoptosis after both the short and continuous infusions, and long-term survival was significantly diminished following continuous compared with the short infusion.

Toxicant exposure in cigarette reducers versus light smokers

BACKGROUND

The extent of exposure to tobacco toxicants in smokers who have reduced their cigarette intake compared with smokers who are light smokers is relatively unknown. The goal of this study is to investigate the occurrence of compensatory smoking in reducers compared with light smokers by measuring toxicant exposure.

METHODS

Participants in two smoking reduction intervention studies (N = 64) were selected for comparison with a group of light smokers (N = 62) who smoked the same number of cigarettes as the reducers. A compensatory smoking score was defined (biomarker level for reducer/biomarker level for light smoker) and calculated for urinary 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) and its glucuronides (total NNAL), metabolites of the tobacco-specific lung carcinogen 4-(methylnitrosamino)-I-(3-pyridyl)-1-butanone, to measure the degree of smoking compensation in reducers when compared with the light smokers.

RESULTS

The mean level of creatinine-adjusted total NNAL for reducers was over twice that of light smokers even when they smoked about the same number of cigarettes per day. The difference of the mean total NNAL concentrations between light smokers and reducers was highly significant (P < 0.0001). Wide variability in total NNAL concentrations was also observed in reducers, with the extent of this variability between light smokers and reducers being significantly different (P = 0.0005). The level of individual reduction was shown to be a consistent predictor of compensatory smoking (r = 0.50; adjusted Ps = 0.002), with greater cigarette reduction associated with more compensation.

CONCLUSIONS

Compensatory smoking limits the harm reduction value of decreased smoking of cigarettes.

A solution for the most basic optimization problem associated with an ROC curve

In a few cases, such as early pregnancy tests, the test results are dichotomous; many diagnostic tests, however, give results which are not binary. In the diagnosis of prostate cancer, prostate-specific antigen test result is on a continuous scale; or, in radiology, assessment of mammograms is on an ordinal scale. In such cases, the accuracy of the marker or test is often first summarized in a receiver operating characteristic (ROC) curve and then as the area under that curve. The area under the ROC curve, however, only shows the 'potential' of a marker; sooner or later, for practical uses, we still need to dichotomize the test result so that we can classify subjects as 'diseased' or 'healthy'. Finding an 'optimal' cutpoint to dichotomize a continuous marker is desirable and is a very basic problem but, in all or most cases, cutpoints used in practice are arbitrary. The difficulty lies in our failure to define and justify a criterion for optimality. In this paper, we will propose a solution by maximizing a well-known parameter--the Youden's Index--within the framework of the ROC curve.

Relationships between cigarette consumption and biomarkers of tobacco toxin exposure

Epidemiologic studies show a dose-response relationship between cigarettes per day and health outcomes such as heart and lung disease, and health outcomes are related to some biomarkers of tobacco exposure. The objective of this study was to examine the relationships between cigarettes per day and levels of selected biomarkers of tobacco toxin exposure: carbon monoxide (CO), metabolites of the tobacco-specific carcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) and polycyclic aromatic hydrocarbons [total 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) and 1-hydroxypyrene (1-HOP), respectively], and total cotinine (cotinine plus cotinine-N-glucuronide). We did a cross-sectional analysis of merged data from (a) two clinical trials and (b) two cohorts of light smokers (total n = 400). The mean age of participants was 50.4 years and the range of cigarette consumption was 1 to 100/d; however, few subjects smoked >45 cigarettes/d (n = 12). Results show that levels of the biomarkers CO, total NNAL, and total cotinine increase with an increase in the number of cigarettes smoked per day, but not in a linear fashion. 1-HOP is a less discriminating biomarker as levels are relatively stable regardless of the number of cigarettes smoked per day. There is considerable variability in toxin measurement, especially at high levels of smoking. There was a significant correlation between cigarettes per day and total NNAL, 1-HOP, total cotinine, and CO. Total NNAL was highly significantly correlated with total cotinine and CO and also significantly correlated with 1-HOP. These findings suggest that the number of cigarettes smoked per day is not necessarily a reliable measure of toxin exposure and may underestimate tobacco toxin exposure at low levels of smoking or overestimate exposure at high levels of smoking.

Diminished neo-antigen response to keyhole limpet hemocyanin (KLH) vaccines in patients after treatment with chemotherapy or hematopoietic cell transplantation

Relapse is the most common cause of treatment failure for advanced cancer, even those treated with autologous hematopoietic cell transplantation (HCT). Effective tumor-specific immunotherapy may decrease relapse, however, this will fail if the immune system is unable to respond. We developed a strategy to test immune responses with a single injection of the bona fide neo-antigen KLH. The model was first tested in 37 normal volunteers using three KLH vaccines: Intracel KLH, Biosyn KLH, and Biosyn KLH + adjuvant. Despite finding the immunogenic epitope conserved in both products, intact Intracel KLH induced a better response compared to a purified 350/390 kDA subunit of KLH contained in the Biosyn KLH product. Addition of a synthetic oil adjuvant (Montanide ISA51) restored the response to a single injection of Biosyn KLH. A quantitative readout measured by a KLH-specific cellular and humoral response with isotype switching 1 month after KLH vaccination was established. To test the integrity of the adaptive immune response in cancer patients, we vaccinated 14 patients post-HCT and 19 patients with advanced cancer with KLH vaccines that elicited a 100% response rate in normal volunteers. In marked contrast to normal subjects, both responses were significantly impaired up to 16 months after autologous HCT with an intermediate response in advanced cancer patients. KLH vaccines are safe and require only a single injection to test neo-antigen responses providing an optimal platform for definitive testing of strategies to improve diminished immune recovery after chemotherapy or post-HCT.

Adding in Vivo Quantitative1H MR Spectroscopy to Improve Diagnostic Accuracy of Breast MR Imaging: Preliminary Results of Observer Performance Study at 4.0 T

PURPOSE

To determine whether the addition of in vivo quantitative hydrogen 1 (1H) magnetic resonance (MR) spectroscopy can improve the radiologist's diagnostic accuracy in interpreting breast MR images to distinguish benign from malignant lesions.

MATERIALS AND METHODS

The study was approved by the institutional review board and, where appropriate, was compliant with the Health Insurance Portability and Accountability Act. All patients provided written informed consent. Fifty-five breast MR imaging cases-one lesion each in 55 patients aged 24-66 years with biopsy-confirmed findings-were retrospectively evaluated by four radiologists. Patients were examined with contrast material-enhanced fat-suppressed T1-weighted 4.0-T MR imaging. The concentration of total choline-containing compounds (tCho) was quantified by using single-voxel 1H MR spectroscopy. For each case, the radiologists were asked to give the percentage probability of malignancy, the Breast Imaging and Reporting Data System category, and a recommendation for patient treatment. Two interpretations were performed for each case: The initial interpretation was based on the lesion's morphologic features and time-signal intensity curve, and the second interpretation was based on the lesion's morphologic features, time-signal intensity curve, and tCho concentration. Receiver operating characteristic (ROC), Wilcoxon signed rank, kappa statistic, and accuracy (based on the area under the ROC curve) analyses were performed.

RESULTS

Of the 55 lesions evaluated, 35 were invasive carcinomas and 20 were benign. The addition of 1H MR spectroscopy resulted in higher sensitivity, specificity, accuracy, and interobserver agreement for all four radiologists. More specifically, two of the four radiologists achieved a significant improvement in sensitivity (P=.03, P=.03), and all four radiologists achieved a significant improvement in accuracy (P = .01, P = .05, P = .009, P < .001).

CONCLUSION

Current study results suggest that the addition of quantitative 1H MR spectroscopy to the breast MR imaging examination may help to improve the radiologist's ability to distinguish benign from malignant breast lesions.

Reduced nicotine distribution from mother to fetal brain in rats vaccinated against nicotine: Time course and influence of nicotine dosing regimen

Nicotine is a teratogen in rats and possibly in humans. Vaccination against nicotine is being studied as a possible treatment for nicotine dependence. The safety of maternal vaccination against nicotine during or prior to pregnancy is not known. In this study, female rats were vaccinated and then administered acute or chronic nicotine during pregnancy at doses simulating nicotine exposure in smokers. Maternal vaccination reduced nicotine distribution to both maternal brain (44-47%) and fetal brain (17-39%) for up to 25 min after a single maternal nicotine dose administered on gestational day (GD) 20, but had a smaller effect on nicotine distribution to brain after continuous nicotine infusion. Nicotine distribution to maternal or fetal brain after repeated nicotine bolus doses was reduced immediately following an individual dose in vaccinated rats, but the chronic accumulation of nicotine in fetal brain was not altered. Nicotine distribution to whole fetus, in contrast to fetal brain, was generally not altered by vaccination. Nicotine-specific antibody concentration in fetal serum was 10% that of maternal serum, and in fetal brain was <1% of maternal serum. Although nicotine transfer to the whole fetus was not reduced by vaccination, protein binding data suggest that nicotine-specific antibody transferred from mother to fetus served to bind nicotine in fetal serum, reduce the unbound nicotine concentration, and thereby reduce nicotine distribution to fetal brain. These data comment on the safety of vaccination against nicotine during pregnancy, and suggest that vaccination may reduce the distribution of nicotine to fetal brain under some nicotine dosing conditions.

Monoclonal nicotine-specific antibodies reduce nicotine distribution to brain in rats: dose- and affinity-response relationships

Vaccination against nicotine is being studied as a potential treatment for nicotine dependence. Some of the limitations of vaccination, such as variability in antibody titer and affinity, might be overcome by instead using passive immunization with nicotine-specific monoclonal antibodies. The effects of antibodies on nicotine distribution to brain were studied using nicotine-specific monoclonal antibodies (NICmAbs) with K(d) values ranging from 60 to 250 nM and a high-affinity polyclonal rabbit antiserum (K(d) = 1.6 nM). Pretreatment with NICmAbs substantially increased the binding of nicotine in serum after a single nicotine dose, reduced the unbound nicotine concentration in serum, and reduced the distribution of nicotine to brain. Efficacy was directly related to antibody affinity for nicotine. Efficacy of the highest affinity NICmAb, NICmAb311, was dose-related, with the highest dose reducing nicotine distribution to brain by 78%. NICmAb311 decreased nicotine clearance by 90% and prolonged the terminal half-life of nicotine by 120%. At equivalent doses, NICmAb311 was less effective than the higher affinity rabbit antiserum but comparable efficacy could be achieved by increasing the NICmAb311 dose. These data suggest that passive immunization with nicotine-specific monoclonal antibodies substantially alters nicotine pharmacokinetics in a manner similar to that previously reported for vaccination against nicotine. Antibody efficacy is a function of both dose and affinity for nicotine.

Quality control and the identification of vaccine responders using ELISA-derived antibody data

First vaccines are traditionally licensed after showing favourable results from phase III efficacy trials. Subsequent competing vaccines, however, have been licensed primarily on the basis of immunogenicity data rather than clinical efficacy. Focusing on pneumococcal vaccines where optical densities are measured and serum antibody concentrations are 'estimated' (from a statistical model) using an immunoglobulin (IgG) enzyme-linked immunosorbent assay (ELISA), the focus of this paper will centre on two highly related issues: the determination of an upper limit for quality control used in the assay methodology (let us call it the maximum tolerated limit or MTL) and the identification of vaccine responders. The goal is to show that these two issues are inter-related, so that investigators could reduce misclassification which would interfere with the eventual comparison of immunogenicity results.

Some statistical methods for investigating the date of birth as a disease indicator

Some methods of temporal statistics are presented and proposed for investigating the date of birth as a disease predictor. A subject's birthday is proposed to be used as a continuous variable with a circular distribution, a special type of interval scale without a true zero point. Three types of endpoints are then considered: a dichotomous endpoint; a continuous endpoint; and time-to-event. A study of otitis media is used for illustration. We found, for example, that children born in late winter to early spring tend to have higher cord blood pneumococcal antibody concentration and lower risk of disease as compared to those born in summer to early fall perhaps due largely to exposure to indoor pollution by pregnant mothers.

A mixture model approach to detecting differentially expressed genes with microarray data

An exciting biological advancement over the past few years is the use of microarray technologies to measure simultaneously the expression levels of thousands of genes. The bottleneck now is how to extract useful information from the resulting large amounts of data. An important and common task in analyzing microarray data is to identify genes with altered expression under two experimental conditions. We propose a nonparametric statistical approach, called the mixture model method (MMM), to handle the problem when there are a small number of replicates under each experimental condition. Specifically, we propose estimating the distributions of a t -type test statistic and its null statistic using finite normal mixture models. A comparison of these two distributions by means of a likelihood ratio test, or simply using the tail distribution of the null statistic, can identify genes with significantly changed expression. Several methods are proposed to effectively control the false positives. The methodology is applied to a data set containing expression levels of 1,176 genes of rats with and without pneumococcal middle ear infection.

Preliminary study on reducing oral moist snuff use

BACKGROUND

Tobacco exposure reduction may be an alternative treatment approach for those tobacco users who are unwilling or unable to quit tobacco use. However, very little information is available on the feasibility of this type of intervention, especially in the area of oral moist snuff tobacco (ST). This pilot study examined whether reducing ST use using various methods can be achieved and whether this reduction results in lower exposure to carcinogens.

METHODS

Moist snuff users (N=40 males) were randomly assigned to 4 mg nicotine gum, non-tobacco mint snuff, brand switching, or elimination of ST use in specific situations. These approaches were used to reduce ST use or nicotine exposure by at least 25% for the first 2 weeks and 50% the subsequent 6 weeks of treatment. Follow-up sessions occurred at 12 and 26 weeks.

RESULTS

Significant reductions were observed in tins per week and cotinine levels across all conditions. Among the intent-to-treat population, the abstinence rate was 15% at 26 weeks. Reduction in nicotine exposure was associated with reduction in exposure to nitrosamines.

CONCLUSION

Reduction in ST use may be a viable approach for those oral moist ST users with no immediate quit plans. Future research in this area is needed.

How many replicates of arrays are required to detect gene expression changes in microarray experiments? A mixture model approach

BACKGROUND

It has been recognized that replicates of arrays (or spots) may be necessary for reliably detecting differentially expressed genes in microarray experiments. However, the often-asked question of how many replicates are required has barely been addressed in the literature. In general, the answer depends on several factors: a given magnitude of expression change, a desired statistical power (that is, probability) to detect it, a specified Type I error rate, and the statistical method being used to detect the change. Here, we discuss how to calculate the number of replicates in the context of applying a nonparametric statistical method, the normal mixture model approach, to detect changes in gene expression.

RESULTS

The methodology is applied to a data set containing expression levels of 1,176 genes in rats with and without pneumococcal middle-ear infection. We illustrate how to calculate the power functions for 2, 4, 6 and 8 replicates.

CONCLUSIONS

The proposed method is potentially useful in designing microarray experiments to discover differentially expressed genes. The same idea can be applied to other statistical methods.

Results of treatment for metastatic osteosarcoma with neoadjuvant chemotherapy and surgery

The purpose of the current study was to define the survival outcome variables for the 85 patients with Stage IIB osteosarcoma treated with neoadjuvant chemotherapy at the authors' institution from 1982 to 1997. A minimum 4-year followup or death was a requisite for inclusion. Forty-three patients were relapse-free survivors and 14 had no evidence of disease at followup for an overall survival of 67%. Twenty-nine patients had thoracotomy and nine have no evidence of disease with a minimum 4-year followup from last thoracotomy. The mean time to metastasis after diagnosis for patients presenting with Stage IIB disease was 12.8 months. There was no difference in the survival for any of the three chemotherapy protocols, used during the 15 years included in this analysis. There was a significant relation between length of time to relapse and survival. For each additional year without relapse, there is an 18% increase in chance of survival. In patients who were treated with thoracotomy, the number of metastatic nodules was a significant predictor of survival; specifically, each nodule increased the risk of death by 43%. A favorable outcome in this cohort of patients is related to the length of time between initiation of therapy and diagnosis of metastasis, and the number of metastatic foci.

Purulent otitis media in children and adults

This study was designed to compare tympanic membrane (TM) and middle ear (ME) pathologies of temporal bones from children and adults with purulent otitis media (POM). Thirty-four temporal bones were used from 22 subjects ages 2 days to 76 years with histopathologic evidence of POM. There were 55 age-matched controls. Histopathologic findings of the TM and ME in children and adults with POM were compared. Clinical histories and the presence of complications were recorded. The incidence of POM was more common in male children than in females. There was a significant increase in the thickness of the posterosuperior and posteroinferior quadrants in children with POM compared to non-OM children. In adults with POM, there was a significant decrease in the thickness of the posteroinferior and anteroinferior quadrants compared to non-OM adults. Children with POM showed a significant increase in the anterioinferior and posteroinferior quadrants and the umbo compared to adults with POM. Pathology of the TM and ME occurred in adults and children, but severity was greater in children. Residual mesenchyme was frequently observed in temporal bones of children. Serious complications such as labyrinthtis and meningitis were observed more frequently in children. All cases with meningitis had labyrinthitis, previous histories of otitis media and had been treated with antibiotics. Although POM occurs in both children and adults, pathologic changes of the middle ear are more severe, and complications (labyrinthitis and meningitis) occur more often in children. Our findings suggest the need to monitor children carefully under the age of 2 years who have POM.

Model-based cluster analysis of microarray gene-expression data

BACKGROUND

Microarray technologies are emerging as a promising tool for genomic studies. The challenge now is how to analyze the resulting large amounts of data. Clustering techniques have been widely applied in analyzing microarray gene-expression data. However, normal mixture model-based cluster analysis has not been widely used for such data, although it has a solid probabilistic foundation. Here, we introduce and illustrate its use in detecting differentially expressed genes. In particular, we do not cluster gene-expression patterns but a summary statistic, the t-statistic.

RESULTS

The method is applied to a data set containing expression levels of 1,176 genes of rats with and without pneumococcal middle-ear infection. Three clusters were found, two of which contain more than 95% genes with almost no altered gene-expression levels, whereas the third one has 30 genes with more or less differential gene-expression levels.

CONCLUSIONS

Our results indicate that model-based clustering of t-statistics (and possibly other summary statistics) can be a useful statistical tool to exploit differential gene expression for microarray data.

Treatment of anal fissure with glyceryl trinitrate in patients referred for surgical management

BACKGROUND

A number of recent studies indicate that anal fissure may be treated by applying glyceryl trinitrate (GTN) ointment. The present study aims to determine the effectiveness and patient acceptability of GTN treatment for patients referred to a consultant surgeon.

METHODS

A prospective study of 65 consecutive patients referred to one surgeon (ALP) over a 12-month period was undertaken. All patients were offered 0.2% GTN ointment to be applied intra-anally four times daily for 4 weeks. Informed consent was obtained and review planned for 4 weeks.

RESULTS

Fourteen patients declined treatment and nine of the 14 (64%) subsequently underwent lateral sphincterotomy. Twelve of the 51 patients (18.5%) who accepted treatment could not complete it due to headache or persisting severe anal pain. Thirty-nine of the 51 patients (77%) were able to complete 4 weeks of treatment. Twenty-two of the 39 reported an improvement in symptoms. A total of 22 patients (43%) who started GTN treatment subsequently underwent lateral sphincterotomy.

CONCLUSIONS

Evidence from the present study suggests that GTN ointment has a place in the management of referred patients with severe and/or chronic anal fissure, but sphincterotomy remains an important treatment option for the majority.

Combination vaccines: choices or chaos? A practitioner's perspective

Combination vaccines are necessary and important for the continuing success of our immunization program, especially when more vaccines are added to the already crowded immunization schedule. However, the multiplicity of competing vaccine products, with various overlapping antigen menu and subtle immunologic differences, may be confusing to the busy practitioner. The cost-effectiveness of the use of combination vaccines will depend on a number of factors, including fair and competitive pricing, appropriate reimbursement for vaccine administration fees, and critical economic algorithms for vaccine selection and purchase.

Anti-inflammatory effect of adenovirus-mediated IkappaBalpha overexpression in respiratory epithelial cells

Many studies into basic biological characteristics of inflammation and tissue injury have implicated pro-inflammatory cytokine-mediated tissue injury in the pathogenesis of inflammatory lung diseases. Because transcription of most proinflammatory cytokines is dependent on the activation of nuclear factor (NF)-kappaB, NF-kappaB could be a good potential target to suppress the cytokine cascade. Cytokine-induced activation of NF-kappaB requires phosphorylation and subsequent degradation of IkappaBa. Therefore, the blocking NF-kappaB activation by IkappaBalpha could inhibit the pro-inflammatory cytokine-induced tissue injury. To evaluate whether blocking of NF-kappaB activation shows an anti-inflammatory effect, this study investigated the effect of adenovirus-mediated overexpression of IkappaBalpha super-repressor (IkappaBalpha-SR) on the pro-inflammatory cytokine expression in respiratory epithelial cells. The transduction efficiency of adenovirus was >90% in both A549 and NCI-H157 cells. Ad5IkappaBalpha-SR-transduced cells expressed high levels of IkappaBalpha-SR, which was resistant to tumour necrosis factor (TNF)-alpha-induced degradation. Adenovirus-mediated overexpression of IkappaBalpha-SR blocked cytokine-induced nuclear translocation of p65 and NF-kappaB deoxyribonucleic acid binding activity without affecting total cellular expression level of NF-kappaB. Ad5IkappaBalpha-SR transduction suppressed cytokine-induced interleukin-8 and TNF-alpha expressions at both ribonucleic acid and protein levels. These results suggest that blocking the nuclear factor-kappaB pathway by adenovirus-mediated overexpression of IkappaBalpha-super-repressor shows an effective anti-inflammatory effect in respiratory epithelial cells.

Bordetella pertussis detection by spectrofluorometry using polymerase chain reaction (PCR) and a molecular beacon probe

Bordetella pertussis was detected by spectrofluorometry following PCR incorporating a molecular beacon probe in the reaction. A DNA fragment from the tandem repeat sequence region (IS 481) of the genome of B. pertussis was amplified in presence of the probe complementary to an internal segment of the amplified DNA fragment. Fluorescein (FAM) and DABCYL were used as the fluorophore and quencher in the probe. The probe was characterized for its signal to noise ratio by homogeneous solution hybridization with a complementary oligonucleotide. Measurement of fluorescent signal at the emission maxima of FAM, immediately after a PCR was used to detect the B. pertussis target, with no additional steps. Presence of B. pertussis in a sample was also examined by agarose gel electrophoresis of the PCR product. A serial diluted stock of B. pertussis (ATCC strain #9797) and fourteen clinical isolates of B. pertussis were examined. The sensitivity of detection by fluorescent measurement was found to be at least in the range of 0.01-0.1 CFU per 10 microl of the sample and was equal to or better than that detected by agarose gel analysis.

Patient satisfaction after surgical treatment for fistula-in-ano

PURPOSE

The surgical treatment of fistula-in-ano frequently results in recurrence of the fistula or postoperative anal incontinence. Despite these problems, most patients are satisfied with the results of their surgery. To clarify this apparent discrepancy, we attempted to identify factors that affect patient's lifestyles and may contribute to their satisfaction.

METHODS

A questionnaire was mailed to 624 patients surgically treated for cryptoglandular fistula-in-ano at the University of Minnesota during a five-year period. Three hundred seventy-five patients returned their questionnaires. Patients who were followed up for a minimum of one year were included in this retrospective study. Associations between postoperative complications and patient satisfaction were identified by chi-squared tests and multiple logistic regression. Attributable fractions for patient dissatisfaction were calculated using study population dissatisfaction rates.

RESULTS

Patient satisfaction was strongly associated with fistula recurrence, difficulty holding gas, soiling of undergarment, and accidental bowel movements. Effects of incontinence on patient quality of life were also significantly associated with patient satisfaction as was the number of lifestyle activities affected by incontinence. Patients with fistula recurrence reported a higher dissatisfaction rate (61 percent) than did patients with anal incontinence (24 percent), but the attributable fraction of dissatisfaction for incontinence (84 percent) was greater than that for fistula recurrence (33 percent). Patient satisfaction was not significantly associated with age, gender, history of previous fistula surgery, type of fistula, surgical procedure, time since surgery, or operating surgeon.

CONCLUSION

Patient satisfaction after surgical treatment for fistula-in-ano is associated with recurrence of the fistula, the development of anal incontinence, and with the effects of anal incontinence on patient lifestyle. In our series of patients treated mainly with laying open of the fistula tract, patients with fistula recurrence had a higher dissatisfaction rate than did patients with anal incontinence. However, because anal incontinence was more prevalent than fistula recurrence, a higher fraction of dissatisfaction was attributable to anal incontinence.