Which endpoint to choose ?(in phase II sarcoma clinical trials)

George D. Demetri, MD Dana-Farber / Harvard Cancer Center, Boston Mass. USA

forRobert Maki, MD PhD in absentiaMount Sinai School of Medicine

New York, NY, USA

(and also in other sarcoma trials!)

Tell me! What is the answer?

Well, what is the question?

Example: Is this randomized study design definitive proof of activity?

Ovarian cancer xenografts in mice treated with cyclopamine or saline

n = 4

n = 4

McCann CK et al. PLoS One 2011; 6(11): e28077

{probably not good enough for FDA approval}4

Example: Is this randomized study design definitive proof of activity?

Citrus fruit dietary supplementation in Sailors with Scurvy!

n = 8

n = 4

Lind 1747 (published in summary, in posteriori){probably not good enough for FDA approval}

5

Intervention

ActiveDisease

100%

And so it is with phase II designs.

• It depends on the question…• Your choice of endpoint is the most

important decision you make in the design of a (phase II) clinical trial

Phase I / II study general principles• Treat a group of patients, typically 20-100, to obtain safety

data• Identify activity (or not)

– Got a great biomarker? YIPPEE!!!! (e.g. viral load in HIV)– Radiological change typically used in solid tumors– Radiological, hematological, molecular parameters for heme

malignancies– Perhaps the most common stage of drug development abandonment

• Proceed to phase III if sufficient activity– Response rate often highest in phase II, lower in single center phase III,

lowest in cooperative group phase III

• Bias is inherent in a group of highly-selected patients– Often no comparison group– Short term therapy: for metastatic disease, most patients often off

treatment within 6-8 weeks– ( How does one identify toxicity in patients treated longer? ) 7

What is your goal?

• Is this a proof-of-concept study?– First phase I or phase II in humans– Often single agent, single arm study– Phase IB or Phase IIA

8

Phase II Trial in “Cancer”

1972

Doxorubicin ActivityNoted in

Sarcomas

Phase II Trial in “Cancer”

1972

Doxorubicin ActivityNoted in

Sarcomas

Phase II in “Cancer”

1972

Doxorubicin and DTICActivityNoted in

Sarcomas

What is your goal?

• Is this a proof-of-concept study?– First phase I or phase II in humans– Often single agent, single arm study– Phase IB or Phase IIA

• Are you trying to rule in or rule out activity for further development?– Probably most reliable with a randomized study– Can compare against other therapy or placebo– Relaxed type I and type II errors (vs. phase III)– Phase IIB

12

13

Endpoint options

• “Progression-free survival” (PFS): commonly used– PFS: time from treatment initiation to tumor progression or death

from any cause, with censoring of patients who are lost to follow-up

• “Time to tumor progression” (TTP): used much less often– TTP: the only event of interest is disease progression

• Response rate (WHO, RECIST, modified RECIST, Choi…) • Biomarker

– Disease marker definitely tied to outcomes [e.g. viral load in HIV]– Tumor marker [e.g. PSA]– Imaging [e.g. PET SUVmax]

• Patient-reported outcomes• Aim: To test impact of study intervention on

“how a patient feels, functions or survives”

How do I assess thee? Let me count the ways (…well, two)

Landmark analysisTime-to-event analysis

15

Time to event data vs. landmark analysisMore data Data are lost

p<0.05 p>0.05p>0.05

Which type of “phase II” study?

• One stage• 2, 3, … n stage• Continuous monitoring__________________________________

• Response adaptive randomization• Phase I-II• Phase II-III “seamless”• Randomized discontinuation

16

A brief history of clinical trials

18

Inscription:

Meester snyt die keye rasMyne name Is Lubbert Das

Master, cut away the stone;My name is Lubbert Das

H Bosch. The Cure of Folly. ~ 1494

Early Clinical Trial

Phase II Investigational device study

Shut down by IRB for:

• Consent from spouse not sufficient• Failure to file annual report• History of basal cell cancer 3 yrs ago made patient ineligible per entry criteria.

One-stage design

19

n patients

Does this drug work?

(Does your dog hunt? Art Skarin)

2-stage design

20

n patients m patients

Gehan EA et al. J Chronic Dis 1961; 13: 346

Preliminary stage Follow-up stage

Rejects completely inactive treatments more rapidly

“Optimized” 2-stage design: Simon

21

n patients m patients

Simon R. 1989; Control Clin Trials 10: 1

• Binary outcome (Response or not)• Sample size minimized for given type I, type II

errors• Study terminated only for early lack of activity

• Very commonly used in oncology

Off to the races!

22

n patients

m patients

p patients

n patients

3 stages

Analyze after every patient:continuous monitoring

Enign LG et al. Stats Med 1994;13: 1727Thall PF and Sung HG 1998; 17: 1563

To randomize & randomize not

• Using RECIST tumor response– Monotherapy?– Combination therapy?– In each case randomization can help, but with IIA designs

single arm studies are often used

• PFS– Not universally validated as a validated (earlier, more

direct) endpoint of clinical benefit compared to overall survival

– Usually requires randomization vs another therapy– Key issues: time-based restaging (lead time bias) and

variations in underlying disease biology (well diff liposarc…..wild type GIST…)

23

“Mít a nemít”, 1944

Randomizations: graphically

24

A

B

R Other Rx

Simple

B

A

R

Other Rx

B

1-way crossover

B

A

R OtherRx

B

A

2-way crossover

A R OtherRx

nil

A

Randomized discontinuation

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Phase II: What to do?

• Try to randomize• Sometimes not practical to randomize

– Very rare sarcoma subtype– Can’t accrue sufficient number to show a small difference– Hey, it’s O.K….

Prospective data are better than retrospective data

• Bayesian designs: useful to choose therapies for further study (I-SPY 2, BATTLE, etc.)– May be difficult to use for regulatory approval based on very

real concerns regarding patient referral bias over time– Randomization as a function of drug– Randomization as a function of biomarker

• Weigh your options, call a friend or twelve…

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Phase III: Be Happy?

• Try to avoid expensive phase III failures!• Set a high bar in Phase II before going to Phase III

in order to minimize risk of phase III failure– Most signals of activity are less obvious in phase III trials

than they were in phase II.

• Decide what is truly clinically important for a patient– And then be honest about whether you think you can

actually achieve it based on available data…

• Do you really need a phase III trial to prove benefit to patients?– If you think “no”, you had better have darned great data!

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Conclusion : Choose your trial design with care