Presentation on theme: "Clinical Validation of Prognostic Biomarkers of Risk and Predictive Biomarkers of Drug Efficacy or Safety Gene Pennello, Ph.D. Team Leader, Diagnostics."— Presentation transcript:
1Clinical Validation of Prognostic Biomarkers of Risk and Predictive Biomarkers of Drug Efficacy or SafetyGene Pennello, Ph.D.Team Leader, Diagnostics Devices BranchDivision of BiostatisticsOffice of Surveillance and BiometricsCenter for Devices and Radiological Health, FDASAMSI Risk Perception Policy Practice Workshop October 3, 2007
2Outline FDA and Device Regulation Types of Biomarkers Validation of DiagnosticsPredictive and Prognostic BiomarkersDefinitions, EndpointsStudy Designs for Predictive BiomarkersProspective Designs – efficiency comparisonProspective-Retrospective DesignsSummary
4What are Medical Devices? An item for treating or diagnosing a health condition whose intended use is not achieved primarily by chemical or biological action within the body (Section 201(h) of the Federal Food Drug & Cosmetic (FD&C) Act).Definition by exclusion: Simply put, a medical device is any medical item for use in humans that is not a drug nor a biological product.
5Example of Medical Devices Relatively Simple Devices tongue depressors thermometers latex gloves simple surgical instrumentsOphthalmic devices intraocular lenses PRK lasers,Radiological devices MRI machines CT scanners digital mammography computer aided detectionCardiovascular Devices pacemakers defibrillators heart valves coronary stents artificial heartsMonitoring Devices glucometers bone densitometersDiagnostic Devices diagnostic test kits for HIV prostate-specific antigen (PSA) test human papillomavirus (HPV) test
6Example of Medical Devices Dental, Ear, Nose, and Throat Devices hearing aids bronchoscopy systemGeneral, Surgical, and Restorative Devices breast implants artificial hips spinal fixation devices artificial skin Emerging technologies multiplex genetic tests (e.g., for multiple mutations or microbes)Genomic and proteomic Dx testsNanotechnological devicesMicrospheres for molecular treatment of cancerRoboticsTheranostics (predictive biomarkers of response or adverse reaction to therapy).Artificial pancreas
7Example of Medical Devices Due to the wide variety in technology, complexity, and intended use, medical devices can present novel statistical design and analysis challenges.
8Device RegulationDecision to approve a PMA application must “rely upon valid scientific evidence to determine whether there is reasonable assurance that the device is safe and effective”.“Valid scientific evidence is evidence from well controlled studies, partially controlled studies and objective trials without matched controls, well documented case histories conducted by qualified experts that there is a reasonable assurance of safety and effectiveness . . .”U.S. Code of Federal Regulations, Title 21 (Food and Drugs), U.S. Government Printing Office, Washington DC, 2001, Part Web address (Accessed February, 2002)
9Device RegulationLeast Burdensome Provisions of FDA Modernization Act (1997)“Secretary shall only request information that is necessary to making substantial equivalence determinations.”“Secretary shall consider, …, the least burdensome appropriate means of evaluating device effectiveness that would have a reasonable likelihood of resulting in approval.”U.S. Code of Federal Regulations, Title 21 (Food and Drugs), U.S. Government Printing Office, Washington DC, 2001, Part 513(i)(1)(D) and 513(a)(3)(D)(ii). Web address
10FDA Least Burdensome Guidance FDA Guidance: The Least Burdensome Provisions of the FDA Modernization Act of 1997: Concept and Principles (2002)“Modern statistical methods may also play an important role in achieving a least burdensome path to market. For example, through the use of Baysian [sic] analyses, studies can be combined in order to help reduce the sample size needed for the experimental and/or control device.”
11Examples of Less Burdensome Non-U.S. dataSurrogate endpoints (e.g., acute follow-up)Interim analysis, Adaptive designBayesian methods (e.g., to reduce sample size)†Propensity Scores for historical controlsSensitivity analysis for missing data. Note, could trade clinical for statistical burden†FDA Draft Guidance for the Use of Bayesian Statistics in Medical Device (released May 23, 2006)
12Least Burdensome Provision Least burdensome provision in FDAMA of 1997 is directed to both medical devices and diagnostics (including biomarkers).
13Device Risk Classification Class I: Devices for which “general controls” provide reasonable assurance of the safety and effectiveness.Class II: “General controls” insufficient, Can establish “special controls” (performance standards [CLIA, ISO], FDA guidance. May require clinical data on a 510(k).Class III: General and special controls insufficient. Life-sustaining/supporting, substantial importance in preventing impairment of human health, potential unreasonable risk of illness or injury. Needs pre-market approval (PMA).
14Post-Market Transformation “Make postmarket data more widely available to Center staff and supplement search and reporting tools”"Investigate the use of data and text mining techniques to identify the "needles in the haystack" by identifying patterns in the incoming data that equate to public health signals.”Example is WebVDME Bayesian data-miningDesign a pilot project to test the usefulness of quantitative decision-making methods for medical device regulation across the total product life cycle
15Types of Biomarkers Diagnostic Early detection (screening), enabling intervention at an earlier and potentially more curable stage than under usual clinical diagnostic conditionsMonitoring of disease response during therapy, with potential for adjusting level of intervention (e.g. dose) on a dynamic and personal basisRisk assessment leading to preventive interventions for those at sufficient riskPrognosis, allowing for more aggressive therapy for patients with poorer prognosisPrediction of safety or efficacy (response) of a therapy, thereby providing guidance in choice of therapy
16Types of Biomarkers Diagnostic Early Detection (screening) Monitoring Risk AssessmentPrognosticPredictive of Safety or EfficacyThe first three are considered together, where the focus is on identifying the disease or condition.
17Types of Biomarkers Diagnostic Early Detection (screening) Monitoring Risk AssessmentPrognosticPredictive of Safety or Efficacy The last three are attempting to predict the future.
18Analytical Validation How well are you measuring the measurand?Precision / ReproducibilityMethod ComparisonLoB, LoD, LoQLinearityStabilityClinical Laboratory Standards Institute (CLSI)(http://www.nccls.org/)
19Clinical Validation (“Qualification”) Does the test have clinical utility?Does it have added value over standard tests (e.g, clinical covariates like age, tumor size, stage)?May or may not require a clinical studyEX. Roche AmplichipCDRH guidance document: “Statistical Guidance on Reporting Results from Studies Evaluating Diagnostic Tests” issued in final form in March, 2007, concerns reporting agreement when there is no perfect standard and also discrepancy resolution.
20Roche AmpliChip CYP450 Test (CDRH de novo 510(k) K042259) Genotypes two cytochrome P450 genes (29 polymorphisms in CYP2D6 gene, 2 in CYP2C19) to provide the predictive phenotype of the metabolic rate for a class of therapeutics metabolized primarily by CYP2D6 or CYP2C19 gene products. The phenotypes are(1) Poor metabolizers: (3) Extensive metabolizers:(2) Intermediate metabolizers: (4) Ultrarapid metabolizers:Cytochrome P450s are a large multi-gene family of enzymes found in the liver, and are linked to the metabolism of approximately 70-80% of all drugs. Among them, the polymorphic CYP2D6 and CYP2C19 genes are responsible for approximately 25% of all CYP450-mediated drug metabolism. A polymorphism in these enzymes can lead to an excessive or prolonged therapeutic effect or drug-related toxicity after a typical dose by failing to clear a drug from the blood or by changing the pattern of metabolism to produce toxic metabolites.
21Adding Value to Standard Clinical Predictors Head to Head: Marker superior to clinical predictors at predicting outcome.Incremental Improvement: Combination superior to clinical predictors alone.Marker Predictive within Clinical Strata: e.g., HR(+, –) significant within age, tumor grade, tumor size groups.
22Multivariate Index Assays An IVDMIA is a device that:Combines the values of multiple variables using an interpretation function to yield a single, patient-specific result (e.g., a “classification,” “score,” “index,” etc.), that is intended for use in the diagnosis of disease or other conditions, or in the cure, mitigation, treatment or prevention of disease, andProvides a result whose derivation is non-transparent and cannot be independently derived or verified by the end user. MIA result could be a binary (dichotomous) (such as yes or no), categorical (such as disease type), ordinal (such as low, medium, high) or a continuous scale.Source: FDA MIA Draft Guidance
23Typical Endpoints for Prognostic or Predictive Biomarkers Time to EventEvent by Time tTreatmentMedian Survival TimeA6 monthsB12 monthsHazard Ratio0.5TreatmentRNot RResponse RateA300.50 (30/60)B10500.13 (10/60)
24Relative Risk vs. Diagnostic Accuracy† Event by Time tRelative Risk3.0 = (30/60)/(10/60)Se0.75 (30/40)Sp0.63 (50/80)PPV0.50 (30/60)NPV0.83 (50/60)ENo E+3060–10504080120MarkerRelative Risk looks good, but Dx accuracy not great → limited clinical utility?†Example taken from Emir, Wieand, Su, Cha, Analysis of repeated markers used to predict progression of cancer Statist. Med., 17, , 1998.
25Hazard Ratio vs. Diagnostic Accuracy† NCCTG Mayo Clinic Study. CA15-3 ratio as diagnostic for progression of breast cancer (as determined by physical exam).Hazard Ratio2.3 (p = )Se0.30 (0.17,0.43)Sp0.82 (0.74,0.89)PPV0.27 (0.21,0.33)†Example taken from Emir, Wieand, Su, Cha, Analysis of repeated markers used to predict progression of cancer Statist. Med., 17, , 1998.
26Diagnostic Performance Sensitivity Specificity (TP rate): (TN rate): FP rate: fraction of fraction of fraction of responders non-responders non-responders who test + who test – who test +Test is useful if TP rate > FP rate, i.e., sensitivity + specificity > 1.EX. Useless test: sensitivity 0.80, specificity 0.20
27Diagnostic Performance Positive Negative predictive predictive value (PPV): value (NPV): 1 – NPV: fraction of fraction of fraction of test +’s who test –’s who test –’s who respond don’t respond respond Test is useful if PPV + NPV > 1EX. Useless test: PPV 0.60, NPV 0.40
28dA ROC curve is a plot of sensitivity (true positive rate) vs. 1-specificity (false positive rate) over all possible cutoff points for the test. The test is informative if the area under the curve is greater than 0.5.
29Prognostic Biomarker (Strong Def’n) Prognostic factor. Informs about an outcome independent of specific treatment (ability of tumor to proliferate, invade, and/or spread).Prognostic biomarker is associated with likelihood of an outcome (e.g., survival, response, recurrence) such that magnitude of association is independent of treatment.On some scale, treatment and biomarker effects are additive, that is, do not interact.
32Prognostic Biomarker (Weak Def’n) Prognostic factor. Informs about an outcome independent of specific treatment (ability of tumor to proliferate, invade, and/or spread).Prognostic biomarker is associated with likelihood of an outcome (e.g., survival, response, recurrence) in a population that is untreated or on a “standard” (non-targeted) treatment.If population is clearly defined, than can use to choose more or less aggressive therapy, but not specific therapies, per se.(often Class II)
34Prognostic BiomarkerHer2-neu for node-negative women with breast cancer – prognostic for recurrenceBreast cancer prognostic test based on microarray gene expression of RNAs extracted from breast tumor tissue to assess a patient’s risk for distant metastasis for women less than 61 with Stage I or II disease with tumor size less than or equal 5.0 cm and who are lymph node negative.(Ref.: Buyse et al. JNCI 98, )
35Agendia Mammaprint Gene Signature for Time to Distant Metastasis (N=302) 5-year:Low risk group: 0.95 ( )High risk group: 0.78 ( )10-year:Low risk group: 0.90 ( )High risk group:0.71 ( )Buyse et al JNCI (2006), 98,
36Proportion alive at 10 years Clinical Gene N Proportion*SignatureLow Risk Low Risk (0.74 to 0.95) SpLow Risk High Risk (0.45 to 0.84) 1–SeHigh Risk Low Risk (0.77 to 0.95) SpHigh Risk High Risk (0.61 to 0.76) 1–Se*Buyse et al JNCI 2006
37Predictive BiomarkerPredictive factor. Implies relative sensitivity or resistance to specific treatments or agents.Predictive biomarker predicts differential effect of treatment on outcome.Treatment and biomarker interact. Predictive biomarker can be useful for selecting specific therapy.
39Predictive Biomarker of Efficacy Marker: HER2/neu Treatment: Trastuzumab (Herceptin)Objective response rate:Herceptin+Chemo Chemo FISH+ 95/176 (54%) /168 (30%) FISH- 19/50 (38%) /57 (39%)Arch. Pathol. Lab Med Jan (ASCO/CAP Guidelines)ASCO/CAP report to improve accuracy in HER2 testing. Report estimates that 20% of Her2 testing may be inaccurate. Objective response rate table as an illustration only. I consider it a weak endpoint for effectiveness of a biomarker.
40Predictive Biomarkers for Safety Predict risk of an adverse event dependent on the biomarkerExampleUGT1A1, cleared by FDA, to predict the risk of neutropenia in patients taking irinotecan for colorectal cancer
41Prospective Study Designs for Predictive Markers Untargeted Design (Reference)Validate Treatment, Marker SimultaneouslyMarker by Treatment DesignTargeted Design (Marker + Subset Only)Marker Strategy DesignHistorical Control
42Untargeted Design (Reference) Test if drug works in entire population.Mixture of marker + and – drug effects.Can store samples if test is not ready.
43Marker by Treatment (Interaction) Design A Randomized Block DesignCan test for biomarker by treatment interaction (predictive biomarker)Test needs to be available before trial ensues.
44Marker by Treatment Design Questions Test Drug Overall and within Marker + Subset0.04, 0.01 tests suggested to control Type I error rate at 0.05 (Simon), but subset could drive overall result.Frequentist multiplicity penalty may preclude subset testing as good business strategy.Statement about drug, not biomarkerTest Marker Overall and within Drug SubsetStatement about marker, not drug.Test for Treatment by Marker InteractionSimultaneously validates drug and marker.
45Targeted Design Test if drug works in subset. Cannot test if marker discriminates. Only PPV available.
46Efficiency of Designs 25% 0% 16x 8x 50% 4x 2x 75% 1.8x 0.9x Relative EfficiencyMarker PrevalenceRelative Efficacy*Targeted Design†Interaction Design ††25%0%16x8x50%4x2x75%1.8x0.9xEfficiency gain depends on marker prevalence, relative efficacy, and difference tested.* Marker – to Marker + Patients†Simon & Maitournam, CCR 2004†† Marker by Treatment Design: Test for Interaction approx. efficiency enriching with half +’s, half –’s.
47Efficiency of Designs 25% 5.2x 1.5x 50% 2.6x 0.7x 75% 0.4x Relative EfficiencyMarker PrevalenceRelative Efficacy*Targeted Design†Interaction Design ††25%5.2x1.5x50%2.6x0.7x75%0.4xEfficiency gain depends on marker prevalence, relative efficacy, and difference tested.* Marker – to Marker + Patients†Simon & Maitournam, CCR 2004†† Marker by Treatment Design: Test for Interaction approx. efficiency enriching with half +’s, half –’s.
48Efficiency of Designs 25% 50% 2.5x 0.3x 1.8x 0.2x 75% 1.3x 0.1x Relative EfficiencyMarker PrevalenceRelative Efficacy*Targeted Design†Interaction Design ††25%50%2.5x0.3x1.8x0.2x75%1.3x0.1xEfficiency gain depends on marker prevalence, relative efficacy, and difference tested.* Marker – to Marker + Patients†Simon & Maitournam, CCR 2004†† Marker by Treatment Design: Test for Interaction approx. efficiency when enriching with half +’s, half –’s.
49Improving Efficiency of Interaction Design Enrich with Test Positives if Pr(+) is lowFind scale such that marker and treatment effects are additiveAdaptive RandomizationBayesian subset analysisIf reader variability (e.g., IHC), then use multiple readers.Prior Information
50Possibilities for Increasing Efficiency of Interaction Design Enrich with Test Positives if Pr(+) is lowEstimates of Sensitivity and Specificity are biased because they depend on Pr(+).Use inverse probability weighting (Horvitz, Thompson, 1952) or Bayes Theorem (Begg, Greenes, 1983) to obtain unbiased estimates.
51A Marker-Based Strategy Pro: More ethical, perhaps. More patients given experimental drug. Test utility based on PPVE, NPVE.Con: Cannot assess test-treatment interaction.
54Possibilities for Increasing Efficiency of Interaction Design TransformationFind a transformation (Box-Cox?) of outcome that makes treatment and effects additive.Can then pool marker effect estimates within treatments A and B.Can also pool drug effect estimates within marker + and marker – ‘s.
55Possibilities for Increasing Efficiency of Interaction Design Adaptive RandomizationAdapt randomization ratio to treatment A and B within biomarker subsets to maximize (a) power, or (b) fraction of patients on better treatmentIf response rate < 0.5 for both treatments, then (a) and (b) are compatible, otherwise in tension.Pr(+) disturbed, so need to adjust Se, Sp
56Possibilities for Increasing Efficiency of Interaction Design Bayesian subset analysis (cf. Dixon, Simon)Subsets modeled as exchangeable via random effects.Subset estimate borrows strength from complement subset, increasing precision of estimate.However, interaction estimate more conservative relative to usual non-Bayesian analysis.
57Bayesian Subset Analysis Power is enhanced to show drug works in marker + subset (blue).Power is enhanced to show marker works (discriminates) in patients taking drug (red)
58Possibilities for Increasing Efficiency of Interaction Design Use Multiple ReadersEGFR IHC test (Dako) and Cetuximab and Panitumumab (Amgen) for Colorectal Cancer. % of cells stained and maximum staining intensity subject to reader variabilityUse multiple readers, account for random reader effects.Multiple Reader, Multiple Case Designs (MRMC) are used for digital mammography systems and computed aided detection (CAD) systemsAnalysis can be difficult.
59Possibilities for Increasing Efficiency of Interaction Design Prior Information (Bayesian analysis)Borrow strength from previous study regarded as exchangeable with current study.
60Marker Based Strategy Design Marker Level (-)Treatment AMarker Based StrategyMarker Level (+)Treatment BRegisterRandomizeTest MarkerNon Marker Based StrategyTreatment ASargent et al., JCO 2005
61Marker Based Strategy Design Marker Level (-)Treatment AMarker Based StrategyMarker Level (+)Treatment BRegisterRandomizeTest MarkerTreatment ANon Marker Based StrategyRandomizeTreatment BSargent et al., JCO 2005
62Marker Based Strategy Design Lacks power: Differential effect comparison diluted because some patients in non-marker-based strategy arm get marker-based treatment (could eliminate these to increase power).Might be best suited if have > 2 treatments or > 2 markersEX. Irinotecan regiment (dose, timing, frequency) determined by UGT1A1 genotype (6/6, 6/7, or 7/7) in colorectal cancer patients.
63Marker Based StrategyIf no gold standard, then can be only way to assess effectiveness of a test.EX. Detection tumor of origin in cancers of unknown primary.No gold standard: IHC, imaging, may fail to identify TOO.Randomize patients to be managed withnew test + standard, orwith standard aloneCompare arms on survival
64Targeted Design w. Historical Control Drug already on market, but has poor response rate.If response rate in marker + study is significantly greater than historical rate, then marker discriminates.LimitationsLacks power because effect diluted.Need to calibrate historical rate to marker + study (adjust for covariates).
65Prospective-Retrospective Designs Prospectively apply marker to stored samples (in retrospect).Can test overall, w. subset, or for interaction.Missing samples could introduce bias.RCT samples. Randomization ensures case and control samples have similar characteristics.Case-control samples. Avoid selection bias by matching on sample processing date, processing sites, etc., and not excluding censored times.Reserve samples only for analytically validated markers that are biologically plausible.
66The Challenge of Multiplicity Multiplicity of classifiersMicroarrays and proteomicsMany predictive models could be built with so many inputs.The challenge is to confirm any such model with an independent data set.A caveat: the independent test data set cannot be continually reused. Great discipline is required in this regard.
67Cross-Validation Pitfall Simon, Radmacher, Dobbin, McShane (2003), Pitfalls in the Use of DNA Microarray Data for Diagnostic and Prognostic Classification, JNCI, 95 (1)
68Summary RemarksHow to assess a test or biomarker is well-known, but not as well-known in therapeutic circles.Need to assess whether the biomarker adds anything to what we already know.The number of possibly good biomarker candidates is enormous but great care is needed in restricting the search.
69Summary RemarksNeed to encourage least burdensome approaches to validating biomarkers without compromising level of evidenceEssential to confirm marker in independent datasetStudies to demonstrate informativeness of a biomarker can be quite difficult to design, conduct and analyze.
70Acknowledgements CDRH Division of Biostatistics (DBS) Greg Campbell, Division DirectorDiagnostic Devices Branch (DDB)Lakshmi Vishnuvajjala, Branch ChiefEstelle Russek-Cohen, Team LeaderGene Pennello, Team LeaderBipasa Biswas Kyungsook Kim,Harry Bushar Samir LababidiArkendra De Kristen MeierShanti Gomatam Kyunghee SongThomas Gwise Rong Tang
71More ReferencesSargent et al (2005). Clinical trial designs for predictive marker validation in cancer treatment trials. J Clin Oncol 23:Pennello & Vishnuvajjala (2005). Statistical design and analysis issues with pharmacogenomic drug-diagnostic co-development, In American Stat. Assoc Proc. of the Biopharm. Section, Joint Statistical Meetings, Minneapolis, MN, August, 2005; American Stat. Assoc.: Alexandria, VA.FDA Drug-Diagnostic Co-Development Concept Paper. April