Mutation burden and other molecular markers of prognosis in colorectal cancer treated with curative intent: results from the QUASAR 2 clinical trial and an Australian community-based series.

BACKGROUND: Molecular indicators of colorectal cancer prognosis have been assessed in several studies, but most analyses have been restricted to a handful of markers. We aimed to identify prognostic biomarkers for colorectal cancer by sequencing panels of multiple driver genes. METHODS: In stage II or III colorectal cancers from the QUASAR 2 open-label randomised phase 3 clinical trial and an Australian community-based series, we used targeted next-generation sequencing of 82 and 113 genes, respectively, including the main colorectal cancer drivers. We investigated molecular pathways of tumorigenesis, and analysed individual driver gene mutations, combinations of mutations, or global measures such as microsatellite instability (MSI) and mutation burden (total number of non-synonymous mutations and coding indels) for associations with relapse-free survival in univariable and multivariable models, principally Cox proportional hazards models. FINDINGS: In QUASAR 2 (511 tumours), TP53, KRAS, BRAF, and GNAS mutations were independently associated with shorter relapse-free survival (p<0·035 in all cases), and total somatic mutation burden with longer survival (hazard ratio [HR] 0·81 [95% CI 0·68-0·96]; p=0·014). MSI was not independently associated with survival (HR 1·12 [95% CI 0·57-2·19]; p=0·75). We successfully validated these associations in the Australian sample set (296 tumours). In a combined analysis of both the QUASAR 2 and the Australian sample sets, mutation burden was also associated with longer survival (HR 0·84 [95% CI 0·74-0·94]; p=0·004) after exclusion of MSI-positive and POLE mutant tumours. In an extended analysis of 1732 QUASAR 2 and Australian colorectal cancers for which KRAS, BRAF, and MSI status were available, KRAS and BRAF mutations were specifically associated with poor prognosis in MSI-negative cancers. MSI-positive cancers with KRAS or BRAF mutations had better prognosis than MSI-negative cancers that were wild-type for KRAS or BRAF. Mutations in the genes NF1 and NRAS from the MAPK pathway co-occurred, and mutations in the DNA damage-response genes TP53 and ATM were mutually exclusive. We compared a prognostic model based on the gold standard of clinicopathological variables and MSI with our new model incorporating clinicopathological variables, mutation burden, and driver mutations in KRAS, BRAF, and TP53. In both QUASAR 2 and the Australian cohort, our new model was significantly better (p=0·00004 and p=0·0057, respectively, based on a likelihood ratio test). INTERPRETATION: Multigene panels identified two previously unreported prognostic associations in colorectal cancer involving TP53 mutation and total mutation burden, and confirmed associations with KRAS and BRAF. Even a modest-sized gene panel can provide important information for use in clinical practice and outperform MSI-based prognostic models. FUNDING: UK Technology Strategy Board, National Institute for Health Research Oxford Biomedical Research Centre, Cancer Australia Project, Cancer Council Victoria, Ludwig Institute for Cancer Research, Victorian Government.

The value of additional bevacizumab in patients with high-risk stroma-high colon cancer. A study within the QUASAR2 trial, an open-label randomized phase 3 trial.

INTRODUCTION: Patients with a high stroma percentage within the primary tumor have a poor prognosis. In this study, we investigate whether anti-angiogenic therapy might improve survival of patients with a stroma-high profile with potentially increased angiogenesis. MATERIALS AND METHODS: Tissue samples of the primary tumor of 965 colon cancer patients participating in the QUASAR2 trial were analyzed for tumor-stroma ratio (TSR). Stroma-high (>50%) and stroma-low (≤50%) groups were evaluated with respect to survival. RESULTS: Disease free survival (DFS) was significantly lower in the stroma-high group (HR 1.53, 95%CI 1.19-1.95, P = 0.001). No difference in DFS was seen with respect to treatment with capecitabine alone (CAP) or capecitabine with bevacizumab (CAPBEV) (Stroma-high HR 1.00, 95%CI 0.69-1.46, P = 0.996; stroma-low HR 1.02, 95%CI 0.75-1.41, P = 0.883). A significant difference in survival was seen comparing groups with or without vascular invasion (DFS P < 0.001). A correlation between vascular invasion and stroma-high was seen (χ2 -test P = 0.043). DISCUSSION AND CONCLUSIONS: The TSR confirmed to be a strong prognosticator for disease-free survival in a selected high-risk patient population. No benefit was found in response to treatment with bevacizumab when stratified for TSR. TSR showed to have an additional prognostic value in patients with vascular invasion present in the primary tumor.

Aberrant P53 expression lacks prognostic or predictive significance in colorectal cancer: results from the VICTOR trial.

AIM: Biomarkers with prognostic and predictive value can help stratify patients with colorectal cancer (CRC) into appropriate treatment groups. We sought to evaluate the clinical utility of P53 protein expression as a biomarker in VICTOR, a large phase III trial of rofecoxib in stage II and III CRC. PATIENTS AND METHODS: Tissue micro arrays were constructed from 884 tumors and the expression of P53 was examined by immunohistochemistry. Tumors were dichotomised as either P53-positive (nuclear expression in >10% of cells or the 'absent' pattern, both representing TP53 mutation) or P53-negative (nuclear expression in <10% of cells). RESULTS: Aberrant P53 expression was found in 65% (482/740) of patients. It was associated with distal location (p<0.001) and stage III disease (p<0.001). No effect was observed on disease-free or overall survival, and there was no interaction with chemotherapy or radiotherapy. CONCLUSION: Analysis of P53 expression in the patients recruited to the VICTOR trial confirmed that P53 expression is associated with site and stage of CRC. However, independently, this biomarker has neither prognostic nor predictive utility in this cohort of patients.

Differential Efficacy of Nicotine Replacement Among Overweight and Obese Women Smokers.

INTRODUCTION: Rates of obesity are higher among more dependent smokers and 37%-65% of smokers seeking cessation treatment are overweight or obese. Overweight or obese smokers may possess metabolic and neurobiological features that contribute to difficulty achieving cessation using front-line nicotine replacement products. Attention to factors that facilitate effective cessation treatment in this vulnerable population is needed to significantly reduce mortality risk among overweight and obese smokers. METHOD: This secondary analysis of 2 large trials of transdermal nicotine replacement in general medical practices evaluated the hypothesis that higher body mass index (BMI) would moderate the efficacy of the nicotine patch. We examined the potential for gender to further moderate the relationship between BMI and treatment efficacy. RESULTS: In the placebo controlled trial (N = 1,621), 21-mg patch was no more effective than placebo for assisting biochemically verified point prevalence abstinence up to 1 year after quitting for women with higher BMI, but appeared to be effective for men at normal or high BMI (gender × BMI beta = -0.22, p = .004). We did not find differential long-term cessation outcomes among male or female smokers in the 15-mg patch trial (n = 705). However, we observed significantly higher rates of early lapse among women with higher BMI treated with nicotine patch across both trials. CONCLUSION: These results suggest that increased BMI may affect the efficacy of nicotine patch on reducing risk of early lapse in women. Additional research is needed to explore mechanisms of risk for decreased efficacy of this commonly used cessation aid.

Investigating the possible causal association of smoking with depression and anxiety using Mendelian randomisation meta-analysis: the CARTA consortium.

OBJECTIVES: To investigate whether associations of smoking with depression and anxiety are likely to be causal, using a Mendelian randomisation approach. DESIGN: Mendelian randomisation meta-analyses using a genetic variant (rs16969968/rs1051730) as a proxy for smoking heaviness, and observational meta-analyses of the associations of smoking status and smoking heaviness with depression, anxiety and psychological distress. PARTICIPANTS: Current, former and never smokers of European ancestry aged ≥16 years from 25 studies in the Consortium for Causal Analysis Research in Tobacco and Alcohol (CARTA). PRIMARY OUTCOME MEASURES: Binary definitions of depression, anxiety and psychological distress assessed by clinical interview, symptom scales or self-reported recall of clinician diagnosis. RESULTS: The analytic sample included up to 58 176 never smokers, 37 428 former smokers and 32 028 current smokers (total N=127 632). In observational analyses, current smokers had 1.85 times greater odds of depression (95% CI 1.65 to 2.07), 1.71 times greater odds of anxiety (95% CI 1.54 to 1.90) and 1.69 times greater odds of psychological distress (95% CI 1.56 to 1.83) than never smokers. Former smokers also had greater odds of depression, anxiety and psychological distress than never smokers. There was evidence for positive associations of smoking heaviness with depression, anxiety and psychological distress (ORs per cigarette per day: 1.03 (95% CI 1.02 to 1.04), 1.03 (95% CI 1.02 to 1.04) and 1.02 (95% CI 1.02 to 1.03) respectively). In Mendelian randomisation analyses, there was no strong evidence that the minor allele of rs16969968/rs1051730 was associated with depression (OR=1.00, 95% CI 0.95 to 1.05), anxiety (OR=1.02, 95% CI 0.97 to 1.07) or psychological distress (OR=1.02, 95% CI 0.98 to 1.06) in current smokers. Results were similar for former smokers. CONCLUSIONS: Findings from Mendelian randomisation analyses do not support a causal role of smoking heaviness in the development of depression and anxiety.

Lack of association of OPRM1 genotype and smoking cessation.

INTRODUCTION: Previous studies have reported an association between µ-opioid receptor (OPRM1) genotype and smoking cessation, with some evidence that the strength of this association depends on dose of nicotine replacement therapy (NRT). We examined whether a single-nucleotide polymorphism in the OPRM1 gene is associated with cessation and whether this variant moderates the effects of higher doses of NRT on abstinence. METHODS: Participants were recruited from the practices of primary care physicians in the United Kingdom. Patients smoking an average of at least 10 cigarettes a day, who wanted to quit and were 18 years or older were eligible for inclusion. A total of N = 633 participants were recruited into the original trial, of whom complete data for pharmacogenetic analyses were available on n = 598. Logistic regression was used to test for the effects of OPRM1 genotype and NRT dose, including the genotype × dose interaction term, on smoking status at 4-week, and 26-week follow-up. Analyses were adjusted for potential confounders. RESULTS: There was no evidence of a genotype effect at either follow-up, and no evidence of a genotype × dose interaction effect. CONCLUSIONS: OPRM1 genotype may not affect the likelihood of smoking cessation, and it may not influence response to high- versus low-dose NRT. OPRM1 may have at most only a modest role in explaining cigarette smoking and cessation.

Association between genetic variants on chromosome 15q25 locus and objective measures of tobacco exposure.

BACKGROUND: Two single-nucleotide polymorphisms, rs1051730 and rs16969968, located within the nicotinic acetylcholine receptor gene cluster on chromosome 15q25 locus, are associated with heaviness of smoking, risk for lung cancer, and other smoking-related health outcomes. Previous studies have typically relied on self-reported smoking behavior, which may not fully capture interindividual variation in tobacco exposure. METHODS: We investigated the association of rs1051730 and rs16969968 genotype (referred to as rs1051730-rs16969968, because these are in perfect linkage disequilibrium and interchangeable) with both self-reported daily cigarette consumption and biochemically measured plasma or serum cotinine levels among cigarette smokers. Summary estimates and descriptive statistical data for 12 364 subjects were obtained from six independent studies, and 2932 smokers were included in the analyses. Linear regression was used to calculate the per-allele association of rs1051730-rs16969968 genotype with cigarette consumption and cotinine levels in current smokers for each study. Meta-analysis of per-allele associations was conducted using a random effects method. The likely resulting association between genotype and lung cancer risk was assessed using published data on the association between cotinine levels and lung cancer risk. All statistical tests were two-sided. RESULTS: Pooled per-allele associations showed that current smokers with one or two copies of the rs1051730-rs16969968 risk allele had increased self-reported cigarette consumption (mean increase in unadjusted number of cigarettes per day per allele = 1.0 cigarette, 95% confidence interval [CI] = 0.57 to 1.43 cigarettes, P = 5.22 × 10(-6)) and cotinine levels (mean increase in unadjusted cotinine levels per allele = 138.72 nmol/L, 95% CI = 97.91 to 179.53 nmol/L, P = 2.71 × 10(-11)). The increase in cotinine levels indicated an increased risk of lung cancer with each additional copy of the rs1051730-rs16969968 risk allele (per-allele odds ratio = 1.31, 95% CI = 1.21 to 1.42). CONCLUSIONS: Our data show a stronger association of rs1051730-rs16969968 genotype with objective measures of tobacco exposure compared with self-reported cigarette consumption. The association of these variants with lung cancer risk is likely to be mediated largely, if not wholly, via tobacco exposure.

Association between nicotinic acetylcholine receptor single nucleotide polymorphisms and smoking cessation.

INTRODUCTION: The α4ß2 nicotinic receptor is of central importance in tobacco dependence, while the homomeric α7 receptor may also play a role. In this candidate gene study, we examine the association between 8 single nucleotide polymorphisms (SNPs) in genes coding for nicotinic acetylcholine receptor subunits α4 (rs1044396, rs2273504, rs2236196, and rs2273502), α7 (rs2133965 and rs4779969), and ß2 (rs2072660 and rs2072661) and smoking abstinence in a cohort of quitters enrolled in a clinical trial of behavioral support. METHODS: Data were obtained from the "Patch in Practice" study, involving 925 smokers in the United Kingdom. All participants were given an 8-week course of 15 mg of transdermal nicotine replacement therapy and blood was taken for genotyping. RESULTS: Logistic regression analyses assessed the association between each selected SNP and smoking abstinence at 4, 12, 26, and 52 weeks. There were no statistically significant associations with smoking cessation success or nicotine intake assessed by plasma cotinine levels. However, rs2273502 was associated with a consistent (though nonsignificant) increase in the odds of abstinence. CONCLUSIONS: There was no compelling evidence that these SNPs were associated with a reduced or higher chance of abstinence. However, rs2273502 may be worth investigating in future studies.

CHRNA3 rs1051730 genotype and short-term smoking cessation.

INTRODUCTION: The rs1051730 genetic variant within the CHRNA5-A3-B4 gene cluster is associated with heaviness of smoking and has recently been reported to be associated with likelihood of stopping smoking. We investigated the potential association of rs1051730 genotype with reduced likelihood of smoking cessation in 2 cohorts of treatment-seeking smokers in primary care in the United Kingdom. METHODS: Data were drawn from 2 clinical trials on which DNA was available. One sample was a randomized placebo-controlled trial of nicotine transdermal patch and the other sample an open-label trial where all participants received nicotine transdermal patch. Smoking status was biochemically verified. Logistic regression was used to assess evidence for association in each sample, and data were combined within a meta-analysis. RESULTS: There was evidence of association of rs1051730 genotype with short-term (4-week) cessation in our open-label trial sample but not our placebo-controlled trial sample. When combined in a meta-analysis, this effect remained. There was no evidence of association at later follow-up intervals. Adjustment for cigarette consumption and tobacco dependence did not alter these results substantially. CONCLUSIONS: Our data, taken together with previous recent studies, provide some support for a weak association between this variant and short-term smoking cessation in treatment-seeking smokers, which does not seem to operate only among those receiving nicotine replacement therapy. Moreover, the rs1051730 variant may not merely operate as a marker for dependence or heaviness of smoking.

Pharmacogenetics of smoking cessation in general practice: results from the patch II and patch in practice trials.

INTRODUCTION: Cigarette smoking remains the leading cause of preventable death worldwide. However, the efficacy of available first-line therapies remains low, particularly in primary care practice where most smokers seek and receive treatment. These observations reinforce the notion that 'one size fits all' smoking cessation therapies may not be optimal. Therefore, a translational research effort was launched by the Imperial Cancer Research Fund (later Cancer Research UK) General Practice Research Group, who led a decade-long research enterprise that examined the influence of pharmacological hypothesis-driven research into genetic influences on drug response for smoking cessation with transdermal nicotine replacement therapy in general practice. METHODS: New and previously published smoking cessation genetic association results of 30 candidate gene polymorphisms genotyped for participants in two transdermal nicotine replacement clinical trials based in UK general practices, which employed an intention to analyze approach. RESULTS: By this high bar, one of the polymorphisms (COMT rs4680) was robust to correction for multiple comparisons. Moreover, future research directions are outlined; and lessons learned as well as best-practice models for designing, analyzing, and translating results into clinical practice are proposed. CONCLUSIONS: The results and lessons learned from this general practice-based pharmacogenetic research programme provide transportable insights at the transition to the second generation of pharmacogenetic and genomic investigations of smoking cessation and its translation to primary care.

Trial Protocol: Using genotype to tailor prescribing of nicotine replacement therapy: a randomised controlled trial assessing impact of communication upon adherence.

BACKGROUND: The behavioural impact of pharmacogenomics is untested; informing smokers of genetic test results for responsiveness to smoking cessation medication may increase adherence to this medication. The objective of this trial is to estimate the impact upon adherence to nicotine replacement therapy (NRT) of informing smokers that their oral dose of NRT has been tailored to a DNA analysis. Hypotheses to be tested are as follows: I Adherence to NRT is greater among smokers informed that their oral dose of NRT is tailored to an analysis of DNA (genotype), compared to one tailored to nicotine dependence questionnaire score (phenotype). II Amongst smokers who fail to quit at six months, motivation to make another quit attempt is lower when informed that their oral dose of NRT was tailored to genotype rather than phenotype. METHODS/DESIGN: An open label, parallel groups randomised trial in which 630 adult smokers (smoking 10 or more cigarettes daily) using National Health Service (NHS) stop smoking services in primary care are randomly allocated to one of two groups:i. NRT oral dose tailored by DNA analysis (OPRM1 gene) (genotype), orii. NRT oral dose tailored by nicotine dependence questionnaire score (phenotype)The primary outcome is proportion of prescribed NRT consumed in the first 28 days following an initial quit attempt, with the secondary outcome being motivation to make another quit attempt, amongst smokers not abstinent at six months. Other outcomes include adherence to NRT in the first seven days and biochemically validated smoking abstinence at six months. The primary outcome will be collected on 630 smokers allowing sufficient power to detect a 7.5% difference in mean proportion of NRT consumed using a two-tailed test at the 5% level of significance between groups. The proportion of all NRT consumed in the first four weeks of quitting will be compared between arms using an independent samples t-test and by estimating the 95% confidence interval for observed between-arm difference in mean NRT consumption (Hypothesis I). Motivation to make another quit attempt will be compared between arms in those failing to quit by six months (Hypothesis II). DISCUSSION: This is the first clinical trial evaluating the behavioural impact on adherence of prescribing medication using genetic rather than phenotypic information. Specific issues regarding the choice of design for trials of interventions of this kind are discussed. TRIAL DETAILS: Funder: Medical Research Council (MRC)Grant number: G0500274. ISRCTN: 14352545. Date trial stated: June 2007. Expected end date: December 2009. Expected reporting date: December 2010.

Phase III randomized trial assessing rofecoxib in the adjuvant setting of colorectal cancer: final results of the VICTOR trial.

PURPOSE: Laboratory and case-control studies suggest a pivotal role for the cyclooxygenase-2 (COX-2) pathway in colorectal carcinogenesis. The purpose of this study was to test whether the COX-2 inhibitor rofecoxib could reduce recurrence and improve survival when administered in the adjuvant setting of colorectal cancer (CRC). PATIENTS AND METHODS: Patients who had undergone potentially curative surgery and completion of adjuvant therapy for stage II and III CRC were randomly assigned to receive rofecoxib (20 mg daily) or placebo. The primary end point was overall survival (OS). Where formalin-fixed paraffin-embedded tumor tissue samples were available, COX-2 expression was evaluated by immunohistochemistry and correlated with clinical outcome. RESULTS: Two thousand four hundred thirty-four patients were entered onto the study. The trial was terminated early because of the worldwide withdrawal of rofecoxib. At this point, 1,167 patients had received rofecoxib and 1,160 patients had received placebo for median treatment durations of 7.4 and 8.2 months, respectively. For the rofecoxib and placebo arms, median follow-up times were 4.84 and 4.85 years, with 241 and 246 deaths and 297 and 329 recurrences, respectively. No difference was demonstrated in OS (hazard ratio [HR] = 0.97; 95% CI, 0.81 to 1.16; P = .75) or recurrence (HR = 0.89; 95% CI, 0.76 to 1.04; P = .15) comparing the two groups. Tumor COX-2 expression by immunohistochemistry was assessed for 871 patients, but neither prognostic nor predictive effects were observed. CONCLUSION: In this study of abbreviated therapy in the adjuvant setting of CRC, rofecoxib did not improve OS or protect from recurrence in unselected patients. In addition, COX-2 expression did not correlate with prognosis overall or predict effectiveness of COX-2 inhibitors.

Genome-wide association for smoking cessation success: participants in the Patch in Practice trial of nicotine replacement.

AIMS: To confirm and extend to primary care settings prior genome-wide association results that distinguish smokers who successfully quit from individuals who were not able to quit smoking in clinical trials. MATERIALS & METHODS: Affymetrix 6.0 Arrays were used to study DNA from successful quitters and matched individuals who did not quit from the Patch in Practice study of 925 smokers in 26 UK general practices who were provided with 15 mg/16 h nicotine-replacement therapy and varying degrees of behavioral support. RESULTS: Only a few SNPs provided results near 'genome-wide' levels of significance. Nominally significant (p < 0.01) SNP results identify the same chromosomal regions identified by prior genome-wide association studies to a much greater extent than expected by chance. CONCLUSION: Ability to change smoking behavior in a general practice setting appears to share substantial underlying genetics with the ability to change this behavior in clinical trials, though the modest sample sizes available for these studies provides some caution to these conclusions.

What is the role and impact of molecular markers on treatment decisions for colorectal cancer in the adjuvant setting?

The new mantra for delivering optimal cancer treatment is "personalized care." This extends beyond the holistic to using germline and somatic tumoral mutations to link a specific therapy to some prognostic or predictive factor which defines a particularly responsive patient subgroup who might benefit most from treatment. Furthermore, inherited polymorphisms have the potential to greatly modulate the side effects of treatment, especially for chemotherapy which has a notoriously narrow therapeutic window.

Lack of association of DRD2 rs1800497 (Taq1A) polymorphism with smoking cessation in a nicotine replacement therapy randomized trial.

INTRODUCTION: We previously reported evidence that the T allele of the dopamine type-2 receptor (DRD2) rs1800497 polymorphism is associated with improved response to nicotine replacement therapy (NRT) relative to placebo and that this association may only be present in females. However, evidence of the poor replication validity of genetic association studies is growing, particularly among those that report subgroup analyses. We therefore attempted to replicate our previous finding of an association between the DRD2 rs1800497 genotype and response to NRT in a new, larger cohort, with greater statistical power. METHODS: Participants were randomly assigned to one of two levels of smoking cessation behavioral support (usual care vs. weekly support). All participants received 8 weeks of 15-mg NRT transdermal patch. RESULTS: The presence of one or more T alleles was associated with a slightly but not significantly lower likelihood of abstinence at 3 and 6 months. We found evidence of a genotype x sex interaction effect. However, stratified analyses indicated a main effect of genotype opposite to the effect reported previously, with females carrying one or more copies of the T allele less likely to be abstinent. DISCUSSION: Our results do not support an association between the DRD2 rs1800497 (Taq1A) polymorphism and response to NRT, contrary to our previous study.

Genetic variation in the serotonin pathway and smoking cessation with nicotine replacement therapy: new data from the Patch in Practice trial and pooled analyses.

The serotonin pathway has been implicated in nicotine dependence and may influence smoking cessation. Therefore, 792 cigarette smokers from the Patch in Practice trial were genotyped for the tryptophan hydroxylase (TPH1 A779C), serotonin transporter (SLC6A45-HTTLPR), and 5-HT1A (HTR1A C-1019G) polymorphisms. Cox regression analysis did not demonstrate significant effects of any of the three genotypes on relapse to smoking: TPH1 (Reference AA; AC: hazard ratio (HR) 0.99, 95% confidence interval (CI) 0.78, 1.24, p=0.90; CC: HR 0.93, 95% CI 0.73, 1.18, p=0.55); 5-HTTLPR (Reference LL; SL: HR 1.01, 95% CI 0.85, 1.20, p=0.90; SS: HR 1.13, 95% CI 0.91, 1.39, p=0.27); HTR1A (Reference CC; CG: HR 1.04, 95% CI 0.86, 1.25, p=0.70; GG: HR 1.01, 95% CI 0.82, 1.24, p=0.93). Moreover, pooled analyses of data from all three extant pharmacogenetic NRT trials (N=1398) found no significant effect of 5-HTTLPR genotype on continuous abstinence at 12-week (Reference LL; SL: odds ratio (OR)=1.25, 95% CI 0.89, 1.74, p=0.19; SS: OR=1.31, 95% CI 0.86, 1.98, p=0.21) or 26-week follow-up (Reference LL; SL: OR=0.93, 95% CI 0.64, 1.33, p=0.68; SS: OR=1.00, 95% CI 0.63, 1.58, p=1.00). These data do not support a statistically or clinically significant moderating effect of these specific 5-HT pathway genetic variants on smoking cessation. However, the possibility remains that other variants in these or other 5-HT genes may influence NRT efficacy for smoking cessation in treatment seeking smokers.

Smoking status moderates the association of the dopamine D4 receptor (DRD4) gene VNTR polymorphism with selective processing of smoking-related cues.

Recently, a variable number of tandem repeats (VNTR) polymorphism in the dopamine D4 receptor (DRD4) gene has been reported to be associated with greater craving and more attention to smoking cues, following a cue-elicited craving procedure. We investigated whether the DRD4 VNTR 7-repeat polymorphism is associated with selective processing of smoking-related stimuli, using a modified Stroop task, and whether smoking status moderates this association. Thirty-one current smokers and 17 ex-smokers attended a single testing session and completed the modified Stroop task. The experimental design included two between-subjects factors of smoking status (current smoker, ex-smoker) and DRD4 genotype (short, long). The DRD4 VNTR polymorphism was associated with selective processing of smoking-related stimuli in ex-smokers but not in current smokers. Our data, therefore, provide partial support for our primary hypothesis and extend on previous work which suggests a role for variation at the DRD4 locus in modulating reactivity to drug-related cues.

Association of COMT Val108/158Met genotype with smoking cessation.

OBJECTIVES: We attempted to extend a previous finding of an association of COMT genotype with response to nicotine-replacement therapy (NRT), in a larger cohort of treatment-seeking smokers, with greater statistical power to detect possible moderating effects of sex. We also investigated the association of the COMT genotype with withdrawal and mood symptoms, to identify possible mediating mechanisms by which the COMT genotype might influence response to NRT. METHODS: Participants were eligible if they were aged 18 years or older, and if they smoked 10 cigarettes per day or more; they were recruited from 26 general practice clinics in Buckinghamshire and Oxfordshire in the United Kingdom. All participants received 8 weeks of 15-mg NRT transdermal patch. Confirmation of abstinence was defined as an exhaled CO of less than 10 parts per million (ppm), or salivary cotinine concentration of less than 15 ng/ml. RESULTS: Cox regression analysis indicated a significant effect of the COMT genotype on relapse into smoking (P=0.001), with shorter times to relapse being observed among the AG (Val/Met) and GG (Val/Val) genotype groups. These effects were observed both during active treatment and as soon as active treatment had ended. The effect, however, was greater, once active treatment had ended, in the subgroup of smokers who had abstained up to this point. We did not observe any evidence of a sex difference in the effect of the COMT genotype. These effects did not seem to be mediated by self-reported withdrawal or mood symptoms. CONCLUSIONS: Our results indicate that the COMT genotype is associated with the likelihood of smoking cessation in smokers treated with the NRT transdermal patch. Future large-scale studies will be required to afford sufficient power to simultaneously investigate the role of multiple genetic variants in treatment responses, and the effects of potential moderating variables on these associations.

A cost-effectiveness analysis of genetic testing of the DRD2 Taq1A polymorphism to aid treatment choice for smoking cessation.

We conducted a cost-effectiveness analysis of genetic testing for smoking cessation, based on data available from the published pharmacogenetic studies of nicotine replacement therapy and bupropion, and a previous cost-effectiveness analysis of smoking cessation treatments. We use multiparameter evidence synthesis methods to combine evidence on cessation by genotype with evidence on cessation irrespective of genotype (which can be written as a function of genotype-specific parameters). Our intention was to explore the most cost-effective approach to prescribing smoking cessation pharmacotherapy, given the hypothetical availability of a test based on a single-gene variant that has been reported to predict treatment response. We considered four types of treatment: nicotine replacement therapy (NRT) pharmacotherapy, bupropion SR pharmacotherapy, combination NRT and bupropion, and standard care as the control. Two scenarios were investigated, one in which the control represented brief advice and the other in which the control represented individual counseling. Strategies that either do not test for dopamine D2 receptor (DRD2) genotype (each individual receives the same treatment), or do test for DRD2 genotype (treatment allocated according to genotype), were evaluated. Our results indicated that the most cost-effective strategy in our hypothetical example of a single-gene test to aid prescription of smoking cessation pharmacotherapy is to prescribe both NRT and bupropion regardless of genotype, as a first-line treatment for smoking cessation. We conclude that it should not be assumed that genetic tailoring will necessarily be more cost-effective than applying the current "one-size-fits-all" model of pharmacotherapy for smoking cessation. In addition, single-gene tests are unlikely to be cost-effective, partly because the predictive value of these tests is likely to be modest.