CtibtiContribution of Bi t ti tiBiostatistics to Designing ... · making clinical trials in...
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C t ib tiC t ib ti ff Bi t ti tiBi t ti ti ttContributionContribution of of BiostatisticsBiostatistics to to Designing Clinical TrialsDesigning Clinical TrialsDesigning Clinical Trials Designing Clinical Trials
Satoshi Morita, PhDSatoshi Morita, PhDDept. of Biostatistics and Epidemiology, Dept. of Biostatistics and Epidemiology,
Yokohama City UniversityYokohama City UniversityYokohama City UniversityYokohama City University
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An elephant in the living roomAn elephant in the living roomA li i l i l i diA li i l i l i diA clinical trial in an uncommon diseaseA clinical trial in an uncommon disease
Low incidence Slow accrual
El#1
Low incidence Slow accrual
Conducting a clinical trial inConducting a clinical trial in such a disease often infeasible
In addition, if low mortality and morbidity
Impractical to achieve adequate power
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Another elephant in the living roomAnother elephant in the living roomN i ll d d iN i ll d d iNo universally accepted endpointNo universally accepted endpoint
Malignant ascites secondary to gastric Cancer: severe end-stage manifestation
of the disease
El#2
of the disease,
poses particular problems to cliniciansEl 2 poses particular problems to clinicians in terms of providing suitable treatment.
HoweverHowever NONO universally accepted measureuniversally accepted measure forforHowever, However, NONO universally accepted measure universally accepted measure for for assessing response to therapy.assessing response to therapy.
Why? No measurable lesions!!Why? No measurable lesions!!Why? No measurable lesions!!Why? No measurable lesions!!Unable to be assessed by the RECIST criteria.Unable to be assessed by the RECIST criteria.
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Today I would like to talk aboutToday I would like to talk aboutToday, I would like to talk about…Today, I would like to talk about…
How biostatistics can contribute to designing and analyzing clinical trials in uncommonand analyzing clinical trials in uncommon diseases?
What biostatisticians have done and are doing for it?doing for it?
Examples: Cancer clinical trialsExamples: Cancer clinical trialspediatric cancer, sarcomasmalignant ascites (gastric cancer)
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Uncommon diseaseUncommon diseaseEx. Pediatric cancerEx. Pediatric cancer
Pediatric doctors often rely on evidence from adultPediatric doctors often rely on evidence from adult clinical trials.
It is natural to consider “borrowing strength” from previous or simultaneous adult studies.previous or simultaneous adult studies.
Clinical trial designs
Prior InformationDose-level(s)Sample size required
External datap q
Trial monitoring (Stop/go decision)(Stop/go decision)
Statistical plan
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Ex. Pediatric phase I trial in Ex. Pediatric phase I trial in metastatic sarcomametastatic sarcoma
Patients with stage IV Ewing’s sarcoma rhabdomyosarcomastage IV Ewing s sarcoma, rhabdomyosarcomaage 1 – 30 yrs
Objective:Objective:to establish “pediatric dosage” of topotecan in combination with Cyclophosphamide (fixed dose)in combination with Cyclophosphamide (fixed dose)
and Melphalan (fixed dose)
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Using prior information / knowledgeUsing prior information / knowledgeUsing prior information / knowledgeUsing prior information / knowledgePrior information:
Optimal dose in adults: 4 mg/m2/dayOptimal dose in adults: 4 mg/m /dayClinical trials in other cancers (ovarian cancer multiple myeloma )(ovarian cancer, multiple myeloma,…)
In the present study,Two dose levels of topotecan: 3.5 and 3.0p
# of patients: at most 20 (Pt accrual: >2 yrs)What if more than two levels?What if more than two levels?
Much more patients! Study design / statistical methodMuch longer time!! Continual reassessment method
A “Bayesian” approach
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A phase II trial for sarcomaA phase II trial for sarcomaA phase II trial for sarcomaA phase II trial for sarcomaThall et al (2003) present a Bayesian study designThall et al. (2003) present a Bayesian study design
for a single-arm phase II trial to examine the efficacy of the targeted drug imatinib for sarcomaefficacy of the targeted drug imatinib for sarcoma with many subtypes.
Sarcoma is uncommon
The goal was to construct a design that allowed the efficacy of imatinib to be evaluatedthe efficacy of imatinib to be evaluated
in the multiple subtypes.
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Subgroups?Subgroups?
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Borrowing strength!!Borrowing strength!!Borrowing strength!!Borrowing strength!!
Hierarchical Bayesian modelHierarchical Bayesian model
1 2 3 4 5 6 7 8 9 1. Synovia
. Leiomyo
3. Malignahistiocy
. Fibrosar
. Liposarc
. Ewing’s
. Osteosa
8. Rhabdosarcom
9. Periphesheath sa
0. Angiosl sarcoma
osarcoma
nt fibrousytoma
rcoma
coma
sarcoma
arcoma
myoa ral nervearcoma
sarcoma
a
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Borrowing strength (cont’d)Borrowing strength (cont’d)Borrowing strength (cont d)Borrowing strength (cont d)G / N d i iGo / No go decision
Conventional design
Hierarchical B i d ldesign
(repeating separate trials)Bayesian model
0/80/5 1/4 3/7 2/8
0/80/5 1/4 3/7 2/8
3/9 2/8 1/8 2/4 1/5
Stop? Continue?
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Borrowing strength (cont’d)Borrowing strength (cont’d)Borrowing strength (cont d)Borrowing strength (cont d)The number of patients requiredThe number of patients required.
Larger # of patients
Hierarchical Conventional design Bayesian modeldesign
(repeating separate trials)
More efficient!!
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Bayesian approaches!!Bayesian approaches!!Bayesian approaches!!Bayesian approaches!!D it thD it th i i b f ti i b f tDespite the everDespite the ever--increasing number of new agents, increasing number of new agents,
the number of patients available for clinical trials the number of patients available for clinical trials remains limited. remains limited.
There is a growing need for statistical methodologies There is a growing need for statistical methodologies g g gg g gthat can “that can “rapidly and efficientlyrapidly and efficiently” evaluate the ” evaluate the clinical efficacy and safety of new agents.clinical efficacy and safety of new agents.y y gy y g
Bayesian approachBayesian approachBayesian approachBayesian approach
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Why Bayesian approaches?Why Bayesian approaches?Why Bayesian approaches?Why Bayesian approaches?
B i h d iB i h d iBayesian methods incorporateBayesian methods incorporateprevious study dataprevious study dataprevious study dataprevious study dataprepre--clinical (animal) dataclinical (animal) data------------i i f tii i f tias prior information.as prior information.
Study design and Data analysisStudy design and Data analysis
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Bayesian approach:Bayesian approach:y ppy ppUpdating a prior by observed dataUpdating a prior by observed data
Previous studies
P t iClinicians’ experience
Prior Data Posterior+
Trial monitoringGo / No go decision
Observed data (+(external) data collected Go / No go decision( (external) data collected
simultaneously)
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A pA p value: data from 12 patientsvalue: data from 12 patientsA pA p--value: data from 12 patientsvalue: data from 12 patients
Clinically NOT meaningful: response rate < 25%
4 responses12 ti t
Response rate = 33%12 patients
p
p-value = 0.36
NOT significant? Negative data?
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P-valueGOD for clinicians?
Source: Rimm &Bortin, ,
Biomedicine, 1978
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P-valueDEVIL for li i i ?clinicians?
EBM
Source: Rimm &Bortin, Biomedicine, 1978
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Bayesian analysis of Bayesian analysis of Prior distributionPrior distributionresponse rateresponse rate
High posterior probability (Response rate > 0 25)High posterior probability (Response rate > 0.25)
Go to the next phase trial
Prior distribution
Response rate
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Prior → PosteriorPrior → PosteriorResponse rateResponse rate
Posterior distribution
Posterior probability (Response rate > 0 25)
Prior + 1 / 3 pts
Posterior probability (Response rate > 0.25)= 60%
Response rate
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Prior → PosteriorPrior → PosteriorResponse rateResponse rate
Posterior distributionPrior + 4 / 12 pts
P t i b bilit (R t 0 25)Posterior probability (Response rate > 0.25)= 80%
Response rate
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Developing a new endpoint to assess Developing a new endpoint to assess t th f li t itt th f li t itresponse to therapy for malignant ascitesresponse to therapy for malignant ascites
M li t itMalignant ascitesbrings a rapid deterioration(Pain, loss of appetite, obstructive symptoms, dyspenea)
A significant negative impact on performance statusand quality of life of patients
Patient-centered response is thereforePatient centered response is therefore more important than tumor response.
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How to measure the response to therapy?How to measure the response to therapy?p pyp py
“G ld t d d”“Gold standard”:Ascitic volume changes by 3D-CT
( i i ll d t ti t th l f(originally used to estimate the volume of organs before and after transplantation)
But, practical limitation…time- and resource-demanding (special equipment, trained radiologists (over 30 mins))
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How to measure the response to therapy? How to measure the response to therapy? (cont’d)(cont’d)(cont d)(cont d)
Approximating the ascitic volume:Approximating the ascitic volume:The Five-Point method, b d ti l CT ibased on conventional CT images
BUT, this alternative does not account for “patient centered changes”patient-centered changes
Use the broadly accepted concept of “Clinical Benefit Response”Clinical Benefit Response
in pancreatic cancer as a prototype!!
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DiureticFrequency of abdominal Girth of Diuretic
consumptionabdominal paracentesis
Girth of abdomen
Ascites fluid
Non-responder Increase in ascites fluid
StableNo change
Responder Decrease in ascites fluid
PS
Non-responder deterioration in PS
Stableno change
Responder improvement in PS
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Clinical Benefit ResponseClinical Benefit Response--Gastric CancerGastric Cancer
Ascites fluidAscites fluidAscites fluidAscites fluid
++ StableStable --
++ ResponderResponder
PSPS StableStablePSPS StableStableNonNon--responderresponder
2626--
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Still challengingStill challengingStill challenging…Still challenging…Bayesian approaches have the potential ofBayesian approaches have the potential of
making clinical trials in uncommon diseasesfeasiblefeasible.“FDA Guidance for the Use of Bayesian Statistics
in Medical Device Clinical Trials”However, how to incorporate external information , p
is NOT fully established.
New endpoint developmentUseful and appealing, but many steps and longUseful and appealing, but many steps and long
time to establish a new endpoint.