The usefulness of liquid biopsy for ctDNA in patients with EGFR-mutant NSCLC during
and after treatment with EGFR-TKIs

Comprehensive
SupportProjectTakuma Yokoyama1, Go Naka2, Hiroo Ishida3, Kazuma Kishi4, Yasuo Ohashi5, Hideo Kunitoh6
1Kyorin University Hospital, Tokyo/Japan, 2National Center for Global Health and Medicine, Tokyo/Japan, 3Showa University School of Medicine, Tokyo/Japan,UMIN#000023248

4Toranomon Hospital, Tokyo/Japan, 5Chuo University, Tokyo/Japan, 6Japanese Red Cross Medical Center, Tokyo/Japan

Study design and purpose

Background 1● Treatment with 1st or 2nd generation EGFR‐TKIs is effective for
NSCLC patients harboring EGFR mutation. However, acquired
resistance is inevitable after a median period of 9 to 14 months.
● Although the resistance mechanisms vary, the most common one isT790M second mutation, which accounts for approximately 60% 1.
● Osimertinib, a 3rd generation EGFR‐TKI targeting EGFR T790M
mutation, is reported to be highly active against T790M positive
NSCLC2 and has been approved in Japan, as well as in the UnitedStates and Europe. Its efficacy is low in T790M‐negative tumors
which got acquired resistance to 1st or 2nd generation EGFR‐TKIs.
● To detect T790M mutation following acquired resistance, re‐biopsyof the tumor is necessary.
● However, re‐biopsy is often difficult and risky, depending on the size
or location of the tumor. There is also a possibility of false‐negative
due to intra‐tumor heterogeneity.

Background 2● The optimal timing of treatment change remains elusive for an“effective” TKI. Many patients could receive benefit from “beyond‐PD” TKI, and minor radiological worsening may not be the best timefor histological exploration, including search for T790M. T790M
may be evident, if ever, only after overt worsening (clinical PD) ofthe disease.
● Frequent re‐biopsies via invasive procedures (bronchoscopy orneedle biopsy) are infeasible in the usual care of NSCLC patients.
● Circulating tumor DNA (ctDNA) detected in the plasma sample isrecognized as a noninvasive biomarker for quantifying themolecular analysis of NSCLC.
● Recently, Cobas EGFR Mutation Test® has been approved in Japan,
using plasma specimens as a companion diagnostic test for thedetection of EGFR mutations to identify such patients with NSCLC;
however, its clinical utility in the trajectories of the patients is yet tobe established.
● Cobas EGFR Mutation Test® is a noninvasive test, but its clinical data,
including detection rate of T790M and the optimal timing of re‐biopsy, are not sufficient.
● T790M monitoring in patients receiving Osimertinib by plasma
ctDNA could give valuable clinical information.

In the prior CSPOR‐LC02 study (Observational study of treatment ofEGFR mutation positive advanced or recurrent NSCLC:UMIN000010538), radiological PD was documented in approximately
80% of the patients. In the 80% of the patients who acquired
resistance to gefitinib, about 60% patients are presumed to have
T790M.
From the above results, this study uses descriptive statistics, and it was
set to 120 cases in consideration of feasibility of research.

 Primary endpoint● The plasma DNA T790M positivity rates by Cobas EGFR Mutation
Test® in the T790M positive tumors patients.
● The plasma DNA T790M positivity rates by Cobas EGFR Mutation
Test® at each clinical point.

 Secondary endpoints● The plasma DNA EGFR Exon 19 deletion or Exon 21 L858 mutation
positivity rates by Cobas EGFR Mutation Test® in clinical courses.
● Time from plasma T790 positivity to tissue T790M positivity in thetissue T790M‐positive cases.
● Response Rate and PFS with Osimertinib.
● Response Rate and PFS with re‐challenge of other EGFR‐TKIs.

Eligibility Criteria
 Key inclusion criteria
1. Histologically confirmed advanced or postoperative recurrent NSCLC
harbouring activating EGFR mutation.
[Definitions of activating EGFR mutation]A) Exon 19 deletion (regardless of subtype)B) Exon 21 L858R
C) Other rare mutations (e.g. Exon 18 G719X)* De novo T790M not excluded.

2. Being treated with an EGFR‐TKI without disease progression, or, To
be treated with an EGFR‐TKI.
3. ECOG PS 0‐2.
4. Age ≥ 20 years
5. Signed informed consent.

 Key exclusion criteria

Study design and purpose Study Design● Multicenter, prospective cohort study in Japan.
● To investigate the diagnostic value of plasma ctDNA of EGFRmutations in the trajectory of patients with EGFR activating mutation‐
positive NSCLC treated with EGFR‐TKIs, including Osimertinib.
Study enrollment
Plasma sampling

RECIST or Clinical PD
Histological sampling
1st treatment of EGFR TKI※

※ 1st treatment of EGFR TKI; non clinical or RECIST PD at enrollment

1st treatment of EGFR TKI【Schedule of plasma sampling】
A) All patients: Baseline and every 1~3 month, until end of treatment with EGFR-TKI
or second biopsy of the lesion of PD revealed no T790M mutation.
B) All patients: At the time of radiological PD to EGFR-TKI.
C) Those who continued to receive 1st treatment of EGFR-TKI beyond radiological
PD: At the time of systemic PD, and/or symptomatic PD.
D) Those who received second biopsy for PD: At the time of the second biopsy.
E) Those who received Osimertinib: Immediately before Osimertinib administration.
F) Those who received another EGFR-TKI than osimertinib as re-challenge:
Immediately before re-challenge administration.

 T790M negative
Beyond PD

1. Prior therapy with an EGFR‐TKI (other than the current therapy, if
being treated with one)

Data Set Enrollment
Between September 30, 2016, and March 10, 2017, at 15 centres
in Japan.
• Enrollment: 122 patients• Ineligible: 1 patient (prior EGFR‐TKI therapy)• Eligible and assessable: 121 patients

Other treatment
 T790M positive
Osimertinib

Patient characteristics Sample size justification

 Data cut‐off for this analysis: August 31, 2017
• Collected CRF of 6 months after enrollment: 67 patients• Not reached 6 months after enrollment: 54 patients• Total 803 plasma samples between September 30, 2016, andSeptember 12, 2017

Characteristics

No. of patients(n = 121)

Gender(Male/Female)

42/79

Age median(range)

72 (40‐92)

ECOG PS
0/1/2

64/54/3

Smoking history
Never/Current/Past/
unknown

80/3/36/2

Clinical stage
IIIA/IIIB/IV/Recurrence

1/3/78/39

Recurrence
Postoperative/irradiation/postoperative andradical irradiation

36/2/1%
34.7/65.3

52.9/44.6/2.5
66.1/2.5/29.8/1.7

92.3/5.1/2.6

EGFR mutation
Ex19 Del
Ex21 L858R
OtherT790M Denovo

6155
5050.445.5
4.10

EGFR samples
Lung
Mediastinal Hilar lymph
Other lymph
Pleural effusion
Other9363154

76.9
5.0
2.5
12.4
3.3

The Metastatic lesion before the therapy of EGFR‐TKI
Brain

33

15.5%

Meningeal dissemination

20.9%

Bone

32

15.0%

Liver

8

3.8%

adrenal gland

4

1.9%

Lung

56

26.3%

Pleural dissemination

32

15.0%

Malignant pleural effusion

29

13.6%

Radiation irradiation site at enrollment
Brain
Bone
Chest (primary)
Chest(metastases)
Other
Brain, boneBone, others
Total
History of Cytotoxic agent
1 regimen
2 regimens
3 regimens
Total20.9%

Other

157.0%

Total

213

100.0%

n103
1102118n182121(%)
55.6%
16.7%
5.6%
5.6%
0.0%
11.1%
5.6%
100.0%
(%)
85.7%
9.5%
4.8%
100.0%

Best overall tumor Response of
1st EGFR‐TKI
CRPRSDPD
NE
Total

%

n43156
19%
21.1%
15.8%
5.3%
26.3%
31.5%
100.0%

n1057
67%
14.9%
85.1%
100.0%

n%

6121
10

60.0%
10.0%
20.0%
10.0%
100.0%

n%

42
4
10

40.0%
20.0%
40.0%
100.0%

Treatment with 1st EGFR‐TKI
Gefitinib
Erlotinib
Afatinib
Totaln504031121(%)
41.3%
33.1%
25.6%
100.0%

1st Re‐biopsy (histological samples)
YesNoTotal

CRPRSDNE
Total

1071
1210103

9.7%
68.9%
11.7%
9.7%
100.0%

Consort diagram
Ineligible 1 patient
Because of Treatment historyof two different EGFR‐TKIs

Eligible patients (n=121)

Total 803 plasma samples
between September 30, 2016,
and September 12, 2017

plasma sampling (n=121)
Collected CRF of 6 months after
enrollment (n=67)
Continuation of 1st EGFR‐TKI (n=48)

Osimertinib (n=4)

Other treatment (n=9)

The lesion of 1st Re‐biopsy(histological samples)
Lung
Mediastinal Hilar lymph
Pleural effusion
OtherTotal
Detection of EGFR mutationby 1st Re‐biopsy (histological samples)
Positive
Only common mt
Common mt+T790M※
Negative
Total※ No detection of T790 in plasma samples

End of 1st EGFR‐TKI (n=19)

Post treatment after the 1st EGFR‐TKI (n=13)

11.9%
58.2%
14.9%
11.9%
3.0%
100.0%

71.6%
28.4%
100.0%

(%)
85.1%
14.9%
100.0%%

839108267nn10318121n%481967

Status of EGFR‐TKI at enrollment
Using before registration
Using after registration
Total

Best overall tumor Response of
1st EGFR‐TKI at enrollment

nTreatment status of 6 months afterenrollment
Continuation of 1st EGFR‐TKI
End of 1st EGFR‐TKI
Total
Post treatment after the 1st EGFR‐TKI
Osimertinib
EGFR‐TKI (other Osimertinib)
EGFR‐TKI+Bevacizumab
Platinum regimen
NoneTotal

1st EGFR-TKI at enrollment

Enrollment (n=122)

Pericardial effusion

Results

History of treatment at enrollment

none (n=6)

The treatment after detection of T790M
by histological samples
Osimertinib
Beyond PD
Total

N%

112

50.0%
50.0%
100.0%

Detection of T790M after 1st EGFR‐TKI
treatment by plasma samples
Positive
Negative
Total

n%

11※
110
120

9.1%
90.9%
100.0%※ No detection of T790 by histological samples

The treatment after Detection of T790M
by plasma samples
Osimertinib
Beyond PD
unknown
Total

n%

32611

27.3%
18.2%
54.5%
100.0%

Conclusions● In this multi‐institutional study, periodic monitoring of ctDNA for
EGFR mutation, including T790M, was feasible, with 121 patients.
So far, 803 plasma specimens were collected in 11 months foranalysis of EGFR gene mutations.
● So far, 19 patients got acquired resistance to the initial EGFR‐TKI. Of
those, ctDNA revealed T790M in 11 patients, whereas histologicalre‐biopsy revealed T790M in 2 patients.
● Follow‐up of the patients and accumulation of the data would
reveal value of T790M ctDNA monitoring in EGFR‐TKI‐treatedpatients, including those receiving osimertinib.

Acknowledgment● This study was conducted by Comprehensive Support Project For
Oncology Research (CSPOR) of Public Health Research Foundation.
The study fund was provided to CSPOR with Support from aninvestigator Sponsored Study Programme of AstraZeneca.
● Thanks to all patients and families● Thanks to the staffs and investigators at all institutions‐ Iwate Prefectural Central Hospital‐ Gunma Prefectural Cancer Center‐ National Hospital Organization Shibukawa Medical Center‐ Kasukabe Medical center‐ Japanese Red Cross Saitama Hospital‐ Kyorin University Hospital‐ National Center for Global Health and Medicine‐ Showa University Hospital‐ Respiratory Center Toranomon Hospital‐ Japanese Redcross Medical Center‐ NTT Medical Center Tokyo‐ Mitsui Memorial Hospital‐ Showa University Fujigaoka Hospital‐ Fujisawa City Hospital‐ Kansai Electric Power Hospital

References
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2. Mok et al. N Engl J Med 2017; 376:629‐40
3. 2017 ESMO Abstract LBA2_PR