Efficacy of Adding Trastuzumab to Standard Chemotherapy in Patients With Advanced HER2-negative Gastric Cancer and HER2 Positive Expression in Circulating Tumor Cells
Phase: PHASE2
Conditions: Gastric Cancer Stage IV
Sponsor: AC Camargo Cancer Center

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GASTHER2: Efficacy of adding trastuzumab to standard chemotherapy in 
patients with advanced HER2-negative gastric cancer and HER2 positive 
expression in circulating tumor cells 
  
Study Protocol and Statistical Analysis Plan 
 
 
authors: Mauro DS Donadio¹, Victor Hugo F de Jesus¹, Francisca Giselle R Moura¹, Ângelo B 
Brito¹, Marcos PG Camandaroba¹, Newton Augusto¹, Celso A Mello¹, Tiago C Felismino¹, 
Virgílio Souza¹, Milton JB Silva¹, Michelle LR Dias²,  Ludmilla TD Chinen³, Rachel SP 
Riechelmann¹. 
Departaments: 1- Clinical Oncology; 2- Radiology; 3- International Research Center 
  
 
 
 
 
 
 
08 / November / 2019  
 

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SUMMARY: 
Resume…………………………………………………………………………………..3 
Introduction……………………………………………………………………………..4 
Hypothesis……………………………………………………………………………....7 
Objectives………………………………………………………………………………..8 
Outcomes………………………………………………………………………………..8 
Methods…………………………………………………………………………………9 
Study Population……………………………………………………………………….12 
Treatment………………………………………………………………………………13 
Statistical Analysis Plan………………………………………………………………..15 
Recruitment and Study Duration……………………………………………………...16 
Schedule………………………………………………………………………………..17 
Funding………………………………………………………………………………....18 
Ethical Considerations…………………………………………………………………18 
References……………………………………………………………………………...20 
 
 
 
 
 

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RESUME: BACKGROUND: Gastric cancer is one of the most common cancers and is one of 
the most deadly cancers. Most patients have advanced disease and should receive first-line 
trastuzumab-associated 
chemotherapy 
when 
the 
biopsy 
is 
positive 
for 
immunocytochemical expression and / or HER2 gene amplification. A study conducted by 
our group noted that there may be disagreement in HER2 expression between circulating 
tumor cells (CTCs) and tumor tissue. However, the effectiveness of using anti-HER2 
treatment when only CTC express HER2 is unknown. The present study aims to evaluate the 
expression of HER2 in patients with relapsed or metastatic gastric cancer and what would 
be the efficacy of adding trastuzumab to chemotherapy when tumor tissue is negative for 
HER2, but there is expression of this gene in CTCs. OBJECTIVES: The primary objectives are 
to evaluate HER2 expression in circulating tumor cells of relapsed or metastatic gastric 
cancer patients with negative HER2 expression on tissue biopsy and response to standard 
treatment with combined anti-HER2 chemotherapy in this population. Secondary objectives 
are to assess the prognostic impact of HER2 positivity on circulating tumor cells in advanced 
gastric tumors and to evaluate HER2 expression in CTCs at the time of treatment 
progression.  METHODS: The investigators will prospectively evaluate HER2 expression in 
CTC and its response to treatment with standard chemotherapy and addition of 
trastuzumab in patients with relapsed or metastatic gastric cancer with positive expression 
of HER2 only in CTC. HER2 expression in tissue and in CTC will be evaluated by 
immunocytochemistry. Descriptive statistics will be used to report the results of categorical 
and continuous variables, and respective dispersion measures. Time-to-event variables will 
be reported in Kaplan Meyer medians and curves. EXPECTED RESULTS: Upon completion of 
the study the investigators expect to show the frequency of HER2 expression in this specific 
population, higher radiological response rate with trastuzumab combination compared to 
chemotherapy alone, determine the prognostic impact associated with HER2 expression in 
CTCs and show the frequency of HER2 expression in CTCs at the time of study treatment 
progression. This study may open a new opportunity for anti-HER2 treatment for gastric 
cancer patients. 
Keywords: gastric cancer, HER2, trastuzumab, circulating tumor cells 
INTRODUCTION 

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Gastric cancer is one of the most common cancers worldwide. Its incidence varies 
according to its geographic region, being more common in East Asia, Eastern Europe and 
South America. About 70% of gastric neoplasms occur in developing countries. (1) Globally, 
it is estimated that in 2018 over 1 million cases were diagnosed with about 780,000 deaths, 
making gastric cancer the 5th in frequency and 3rd in mortality. (2,3) In Brazil, 13,540 new 
cases were diagnosed in 2018, being the third leading cause of cancer death in Brazil in 
males. (4) Most patients already have inoperable, advanced or metastatic disease at 
diagnosis, thus requiring palliative treatment. (5) 
Over 90% of stomach tumors are adenocarcinomas and, in terms of histology, 
Lauren's classification subdivided gastric cancer into diffuse (undifferentiated) or intestinal 
cancer (6) and both types have distinct clinical and pathological features. The diffuse type 
occurs in all age groups with equal gender distribution, involves the body or the entire 
stomach and has a greater tendency to invade the gastric wall (resulting in plastic linitis) 
and to metastasize, as well as a faster disease progression and worse prognosis. (7) On the 
other hand, the intestinal type predominates in men and the elderly, occurring 
predominantly in the gastric antrum and notch. Although both subtypes are related to H. 
pylori infection, in the intestinal type the evolution of sequential preneoplastic alterations 
is observed, namely: atrophic gastritis / intestinal metaplasia; dysplasia and 
adenocarcinoma. Such a sequence may not occur in diffuse type. (7,8) There is also a rare 
genetically related type called hereditary diffuse gastric cancer (HDGC) that is not related 
to H. pylori infection. Diffuse-type adenocarcinoma is the major histological subtype of 
HDGC. (9) In addition to diffuse hereditary gastric cancer syndrome, gastric cancer is present 
in the description of several other hereditary syndromes, such as Lynch syndrome, juvenile 
polyposis syndrome, Peutz-Jeghers syndrome, Familial Adenomatous Polyposis, ataxia-
telangiectasia syndrome, Li-Fraumeni and Xeroderma Pigmentosa. (10-14) 
Regardless of association with genetic syndrome or even histological type, it is 
necessary to investigate the amplification of the human epidermal growth factor 2 (HER2) 
gene in the case of recurrent or metastatic gastric cancer. Today of well-defined importance 
in gastric cancer, HER2 was initially recognized 30 years ago as an amplified oncogene in 
over 20% of breast cancers and, after the genomic revolution, has recently been seen to 

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amplify in many other cancers. (15) HER2 is a tyrosine kinase-like receptor that crosses the 
cell membrane of cells, with the extracellular half not coupling to ligands, but designed to 
recognize ligand-activated forms of family members as the factor of human epidermal 
growth (EGFR), HER3 or HER4, leading to dimerization with these receptors. The 
cytoplasmic part of HER2 and its partners contains a kinase domain that triggers HER2 
kinase activity. The end result is phosphorylation at various tyrosine residues and 
recruitment of second messenger proteins for these phosphotyrosines. When the gene is 
amplified in cancer cells, the result is massive overexpression of HER2, which causes 
continuous activation of the various biological pathways that promote cell proliferation. 
(15) 
For 
gastric 
cancer, 
positivity 
for 
HER2 
expression, 
as 
assessed 
by 
immunohistochemistry (IHC) or in situ hybridization immunofluorescence (FISH), may vary 
between 8 and 36% between studies in the literature; However, those studies that 
considered only intestinal histology found positive expression of HER2 between 20 and 30% 
in patients' biopsies. (16) A study conducted at AC Camargo identified 12% HER2 expression 
and 8% amplification in gastric tumors, with greater association with intestinal subtype and 
poor survival. (17) 
Because it has a worse prognosis and has a target drug, treatment of tumors with 
HER2 amplification requires HER2-targeted agents, often in combination with 
chemotherapy or hormone therapies. (15) Trastuzumab-associated chemotherapy (fluoro-
uracil and platinum) is the first-line standard treatment for HER2-positive metastatic gastric 
cancer based on the phase III ToGA study (Trastuzumab for Gastric Cancer). This study 
recruited 594 patients and showed a median overall survival gain of 13.8 months for the 
combination versus 11.1 months in the chemotherapy arm alone (hazard ratio [HR], 0.74; 
95% CI, 0.60 to 0.91; P = 0.0046). Survival gain was even more significant in the HER2 
overexpressed subgroup (IHC 3+ or IHC 2+ with positive FISH), which achieved a median 
overall survival of 16 months. (5) 
Regarding the second line, however, phase III studies failed to demonstrate the 
benefit of using anti-HER2 therapy. In the TyTan study, the addition of lapatinib in the 
second line was not superior to chemotherapy alone. (18) In the GATSBY study, the use of 
trastuzumab entansine was also not superior to taxane chemotherapy. In this study, 77% of 

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patients received first-line anti-HER2 agents. (19) 
Several clinical reasons may explain these disappointing results; One of these is 
resistance acquired after use of anti-HER2-based therapy. Another reason is the loss of 
HER2 expression, as reported in a study by Pietroantonio et al that demonstrated loss of 
HER2 positivity and overexpression in 32% of the tissue samples analyzed after anti-HER2 
therapy. (20) It is already known that in selective breast cancer treatment pressure can 
eradicate HER2-expressing clones and lead to proliferation of those HER2-negative clones, 
a phenomenon that can occur in gastric cancer because of the marked heterogeneity that 
exists in stomach tumors. (21,22) In addition, it is known that HER2 expression discrepancy 
may exist between primary and metastatic or recurrent breast tumors (probably due to 
sample variability). (23) In discordant cases, HER2-positive metastases from negative 
primary tumors are more frequent than the opposite. (20) Therefore, it is recommended 
that metastatic disease on first relapse be biopsied as part of the investigation and HER2 
status should be reevaluated. (24) In cases of gastric cancer, this issue has not been widely 
explored. 
In this sense, the GASTHER 1 study investigated the role of HER2 expression 
reassessment in stomach cancer at primary, metastatic or recurrent sites in patients whose 
primary tumor was initially negative for HER2 expression. The results showed a positive 
rescue of 8.7%, confirming the relevant heterogeneity of HER2 status. (25). 
This heterogeneity, however, may also be associated with the HER2 status 
assessment method. A prospective study in patients with localized gastric adenocarcinoma 
and treated with perioperative chemotherapy at our institution found 69.4% agreement for 
HER2 expression in primary tumor tissue biopsy and in paired circulating tumor cells (CTCs). 
HER2 in CTCs showed higher positivity compared to tumor tissue (43% x 11%). (26) The 
positivity in HER2 CTCs was 60% for HER2-negative localized gastric cancer patients treated 
with perioperative chemotherapy whose disease recurred. Also, HER2 expression in CTCs 
correlated with progression-free survival, but in the tumor tissue the same relationship was 
not found. 
 BACKGROUND 

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Analysis of CTCs from the blood of patients with gastric adenocarcinoma may be 
useful to better understand the behavior of the disease, as well as patients more likely to 
respond to treatment, and may offer a less invasive way of investigating tumor dynamics. 
In addition, prospective evaluation of HER2 expression in CTCs has not been evaluated in 
metastatic gastric cancer, and the frequency with which this expression changes after first-
line treatment with standard regimen with trastuzumab at the time of disease progression. 
Thus, this study is necessary to evaluate the frequency with which these phenomena occur 
and thus expand the knowledge of the dynamics of gastric cancer tumor biology. 
   
Hypothesis: 
Primary: 
1- There is disagreement in HER2 expression positivity between diagnostic tissue biopsy 
(preferably metastasis) and circulating tumor cells in metastatic intestinal cancer. 
2- Positivity for HER2 expression in circulating tumor cells in relapsed or metastatic gastric 
cancer may predict response to standard treatment with trastuzumab combination 
chemotherapy. 
 Secondary: 
1- HER2 expression may have prognostic effect when positive in CTCs. 
2- HER2 expression in CTCs may be modified following treatment with anti-HER2 therapy.  
 
Objectives: 
Primary: 
1- Evaluate HER2 expression in circulating tumor cells of patients with relapsed or 
metastatic gastric cancer with negative HER2 expression on tissue biopsy. 

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2- To evaluate the response to standard treatment with combination chemotherapy with 
trastuzumab in relapsed or metastatic gastric cancer with positive expression of HER2 on 
CTC and negative on tissue biopsy. 
 Secondary: 
1- To verify the prognostic impact of HER2 positivity in circulating tumor cells in advanced 
gastric tumors; 
2- Evaluate HER2 expression in CTCs at the time of progression to standard first-line 
treatment with anti-HER2 therapy in patients who previously had HER2 positivity. 
  
Outcomes: 
Primary: 
1- Frequency of HER2 expression among circulating tumor cells of patients with relapsed or 
metastatic gastric cancer with negative expression of HER2 in tumor tissue (primary or 
metastatic, preferably). 
2- RECIST1.1 radiological response rate following standard treatment with combined 
chemotherapy with trastuzumab in relapsed or metastatic gastric cancer with positive 
expression of HER2 in CTC and negative in tumor tissue. 
Secondary: 
1- Prognostic impact measured by progression-free survival and overall survival using 
standard treatment with trastuzumab combination chemotherapy. 
2- Frequency of HER2 immunocytochemical expression in CTCs at the time of progression 
to standard first-line chemotherapy and trastuzumab treatment. 
  

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Methods: 
Study Design:  
This is a single-phase prospective unicentric phase II study evaluating HER2 
expression in circulating tumor cells and their response to standard treatment with 
trastuzumab combination chemotherapy in cases of positive expression in patients with 
relapsed or metastatic gastric cancer with expression HER2 negative in the tumor tissue. 
Eligible patients who sign the Informed Consent Form (ICF) will be submitted to 
collection of CTCs for immunocytochemical expression (ICC) and HER2 in situ fluorescence 
hybridization test (FISH) at two times: in the diagnosis of relapse or disease untreated first-
line palliative metastatic treatment (for eligibility assessment, see “Eligibility”) and, in 
progression 
after 
standard 
treatment 
of 
platinum-based 
chemotherapy 
and 
fluoropyrimidine and trastuzumab. Eligible patients will be treated with standard 
chemotherapy (FOLFOX schedule every 2 weeks) as per institutional routine, combined with 
experimental use of trastuzumab at the standard dose (3) of 8 mg / kg in the first cycle D1, 
followed by 6 mg / kg every 2 weeks in the remaining cycles until disease progression, 
unacceptable toxicity or withdrawal of consent. The use of trastuzumab for HER2-positive 
gastric cancer is a worldwide standard and widely used in our service for patients with 
supplemental health insurance; Trastuzumab is not available from the Unified Health 
System (SUS). The standard definition of HER2 positive expression is made by 
immunohistochemistry (IHC) or FISH, the latter being performed only if IHQ 2+. FISH will not 
be performed when IHQ 0 or 1+ in tissue biopsy as the investigators will stick to the standard 
procedures of current care. As in this study the investigators will evaluate treatment with 
trastuzumab based on HER2 expression by immunocytochemistry and FISH in the CTCs of 
all participants, the investigators considered this intervention as experimental. Brazilian 
company Libbs, which produces the biosimilar trastuzumab used in AC Camargo, will donate 
the drug and provide insurance to cover any adverse effects associated with trastuzumab. 
The following clinical data will be collected prospectively and structured in a 
password-protected electronic database: gender, age, gastric tumor location (esophageal-
gastric transition, fundus, body or pylorus), ECOG scale performance status, sites 

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metastases, previous treatments, comorbidities (defined as any clinical condition requiring 
pharmacological therapy), concomitant chronic use drugs, body mass index, treatments 
received for metastatic disease (2nd and 3rd lines), response to treatment, dates of 
progression, further treatment and death. 
  
Research Methodology for Circulating Tumor Cells (CTC)  
A 10 ml pre-study peripheral blood sample will be collected for circulating tumor cell 
(CTC) screening and characterization of protein expression by immunocytochemistry. In 
case of results pointing to good accuracy of CTC in this neoplasia, these results can be 
applied as a diagnostic tool for patients with contraindication of tissue biopsy. 
 Isolation and Purification of CTC (blood samples):  
Blood samples collected in EDTA tubes (10 mL) will be processed within 4 hours, diluted 
1:10 in erythrocyte lysis buffer and filtered on the ISET system. After filtration, the 
membranes will be washed with PBS, dried at room temperature, protected from light and 
stored at -20 ° C until the time of analysis. 
  
Immunocytochemistry in ISET Membranes:  
For immunocytochemistry and protein expression analysis, membrane spots will be cut 
and placed in 24-well plates. Each spot will be hydrated with Tris Buffered Saline (TBS) for 
10 minutes. The cells will be permeabilized with 0.2% TBS Triton X-100 for 5 min at room 
temperature. Following a further wash with TBS, the membranes will be incubated for 15 
minutes in the dark at room temperature with a 3% hydrogen peroxide solution and washed 
again with TBS. Then the antibodies to be screened will be applied to the spots and 
incubated for one hour. For negative control, the primary antibody will be omitted. The 
development will be done with Dual long system HRP (DakoTM) and chromogen 
Diaminobenzidine 3,3 '(DAB) (DakoTM). For reading, the spots will be stained with 
hematoxylin for 1 minute and adhered to slides with aqueous mounting medium. CTC will 

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be characterized according to the following criteria: nuclear size equal to or greater than 
16µm, nuclear contour irregularity, presence of visible cytoplasm, high nucleus-cytoplasm 
ratio (> 0.8), as described by Krebs et al. .19 When any of the described criteria is missing, 
the cells will be classified as atypical. Results will be given in CTC number per mL of blood. 
  
FISH on ISET Membranes:  
For FISH and HER2 mRNA expression analysis the investigators will use the ACD 
RNAscope® in situ Hybridization (ISH) 2.5 HD Detection Kit (Brown), previously standardized 
for ISET membrane spots. 5 minutes at room temperature (RT) and then with 1% 
formaldehyde for 5 minutes at RT Subsequent washes between steps will be performed 
with distilled water (2 washes) Membranes with CTCs will be incubated in ScopeHydrogen 
Peroxide RNA (ACD) for 10 minutes. After washing, the membranes will be incubated with 
cytological pepsin (ZytoVision) for 10 minutes at RT the membranes will be washed in 70%, 
90% and 100% ethanol for one minute each. The membranes will be incubated with the 
HER2 mRNA probe in the hybridizer at 40 ° C (wet) for 2 hours From this step, the washes 
will be performed with the 1X Wash Buffer (ACD) (2 washes each step). Incubate the 
membranes with Amp 1 (ACD) for 30 minutes at 40 ° C (wet) in the hybridizer. After washing, 
the investigators will incubate the membranes with Amp 2 (ACD) for 15 minutes at 40 ° C 
(humid) in the hybridizer. Then the investigators will incubate the membranes with Amp 3 
(ACD) for 30 minutes at 40 ° C (wet) in the hybridizer. After washing, the membranes will 
be incubated with Amp 4 (ACD) for 15 minutes at 40 ° C (wet) in the hybridizer. Washing. 
The investigators will incubate the membranes with Amp 5 (ACD) for 30 minutes in T.A. 
Wash. The membranes will be incubated with Amp 6 (ACD) for 15 minutes in T.A. Wash. 
The investigators will mix equal volumes of BROWN-A and BROWN-B (ACD). The 
membranes will be incubated with DAB in the sealed tray for 10 min at RT. The DAB will be 
removed and washed 2X in distilled water. The investigators will incubate in 50% 
hematoxylin (after dilution, lasts 1 week) for 2 min at RT. The investigators will wash 2X with 
distilled water. The slides will be adhered with aqueous mounting medium and coverslip. 
Membrane reading will be performed under a bright field microscope. 

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Study Population 
Eligibility: 
Patients will be recruited from Clinical Oncology outpatient clinics and must meet 
all the criteria below Inclusion and none Exclusion:  
Inclusion criteria 
●    Age 18 or over 
●       Histological diagnosis of recurrent or metastatic gastric cancer 
●       Immunohistochemistry (IHC 0 or 1+) or FISH negative (if IHQ 2+) for HER2 on 
tissue biopsy, according to institutional routine 
●       Candidates to initiate first-line palliative treatment; Previous adjuvant 
treatment is allowed since its termination occurred at least 12 months ago 
●    ECOG performance range 0 to 2 
●       Informed consent form signed by patient or legal representative 
Exclusion Criteria 
●       Patients already on or previously using anti-HER2 therapy 
●       Left ventricular ejection fraction (LVEF) <55% baseline, as already evaluated in 
the gastric cancer routine 
●       Pregnant or lactating women 
●       Patients participating in other experimental drug protocols 
●       Patients who received previous palliative chemotherapy 
●       Another synchronic neoplasia requiring systemic treatment 

Version 2 November 2019 
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Treatment 
The first-line standard treatment for gastric cancer is based on fluorpyrimidine and 
platinum-containing chemotherapy (FOLFOX). When the tumor expresses HER2 3+ on IHC 
or 2+ and is confirmed by FISH, trastuzumab at the standard dose of 8 mg / kg in D1 of the 
first cycle is added, followed by 6 mg / kg every 2 weeks for the remaining cycles until 
disease progression, unacceptable toxicity. (3) The investigators will use the same doses of 
trastuzumab, but HER2 positivity is determined by immunocytochemical expression and 
FISH in CTCs. 
Trastuzumab is a human monoclonal IgG antibody that selectively targets HER2, a 
human epidermal growth factor (EGFR) receptor. Trastuzumab inhibits the growth of HER2 
overexpressing tumor cells on the surface of the breast, gastric, ovarian, lung and prostate 
cancer cells. (27,28) Mechanisms involved include: decreased vascular epithelial growth 
factor (VEGF) production, antibody-dependent cell-mediated cytotoxicity, G0 / G1 cell cycle 
cytotoxicity, and inhibition of signaling pathways. (27) 
Contraindications: 
• history of hypersensitivity reaction to trastuzumab or Chinese hamster ovary cell 
proteins (27) 
Careful: 
• patients with pre-existing cardiac dysfunction or left ventricular ejection fraction 
(LVEF) of 55% or less (27) 
• patients with pre-existing severe lung disease or extensive involvement of the lung 
parenchyma by tumor; Patients who experience dyspnea at rest due to comorbidities or 
advanced neoplasia may be at higher risk of death from infusion reaction. (27) These are 
ineligible for treatment with trastuzumab and often chemotherapy due to poor 
performance status (ECOG> 2). 

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 ADVERSE EFFECTS: 
Trastuzumab has been used by thousands of cancer patients for at least 2 decades. 
Its first indication was in HER2-positive breast cancer and later in gastric cancer. It is 
currently being used in other solid tumors with tumor expression of HER2, such as bile duct 
and colon tumors. It is a safe drug with few risks but requires attention for its cardiotoxic 
effect. Severe trastuzumab-induced cardiotoxicity is described in less than 1% of breast 
cancer patients. Already in patients with stomach tumors, the incidence is anecdotal, most 
likely because the time of use is shorter (approximately 8 to 10 months). Signs and 
symptoms include: dyspnea, cough, paroxysmal nocturnal dyspnea, peripheral edema, 
congestive heart failure (CHF), or reduced LVEF by 10% or more. (27) Trastuzumab cardiac 
dysfunction is cumulative dose related and is reported to be highly reversible. LVEF returns 
to baseline during treatment at 1.5 months after trastuzumab; however, some cases have 
resulted in disabling heart failure, thrombosis and stroke and / or death. (27.30) 
Risk factors for trastuzumab-related cardiotoxicity include: 
• advanced age (> 65 years) 
• a lower left ventricular ejection fraction (LVEF) 
• higher body mass index (> 25) on screening 
  
There is some uncertainty as to whether smoking, diabetes, hypothyroidism, or 
hyperlipidemia are associated with cardiotoxicity following drug use. Prior or concurrent 
irradiation does not increase cardiac events, but may increase the incidence of leukopenia. 
(27) However, there are inadequate long-term data to correlate cardiac dysfunction with 
trastuzumab with simultaneous or prior radiation. (27) Trastuzumab disrupts the HER2 
signaling pathway in the heart, which maintains normal cardiac cell growth, repair and 
survival. This results in changes in cardiac contractility, but does not cause myocardial cell 
death. (31) 
Toxicity management: 

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Suggested management recommended for trastuzumab-related cardiotoxicity 
includes drug retention for approximately 3 weeks if LVEF falls 10 to 15 points below 
baseline and / or below 50%. Trastuzumab may be resumed when LVEF improves. If LVEF 
does not improve within approximately 3 weeks, discontinuation of the drug is considered. 
(27.31) 
LVEF should be evaluated before starting trastuzumab treatment, repeated every 3 
months during treatment, and then every 6 months after the end of treatment, up to 24 
months from the last dose of trastuzumab. 
  
Statistical Analysis Plan  
Statistical plan 
Descriptive statistics will be used to report the results of categorical and continuous 
variables, and respective dispersion measures. Time-to-event variables will be reported in 
Kaplan Meyer medians and curves. 
 Sample size calculation 
To calculate the sample size, the investigators considered HER2 positive expression 
H0 in tumors with negative expression in tissue biopsy of 60%, based on the results 
produced by our group. (13) Two-tailed type I error margin of 10% was considered. With 
these calculations, the sample number will be 85 patients so the investigators can find 50 
cases of HER2 positive expression in CTCs. 
  
Recruitment and Study Duration 
At AC Camargo Cancer Center, 100 new patients with gastric adenocarcinoma are 
treated annually. Considering that 50% correspond to the intestinal type and of these, 80% 
are HER2 negative on tissue biopsy, the investigators estimate to recruit the study 

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population within a maximum of 2 years and to complete the study within 5 years. 
 
 
 
 
 
 
 
 
 
 
 
 
 
Schedule 
TABLE 1. Complete procedural summary of the study after signing the consent form 
Procedure 
Screening 
baseline 
evaluation
* 
D1C2 D1C3 
D1C4 
  
  
D1C5 
D1C6 D1C7 
D1C8... 
PD 
Eligibility Assessment 
  
  
  
  
  
  
Meets eligibility criteria 
x 
x 
  
  
  
  
Demographics, 
medical history and 
previous treatment 
  
x 
  
  
  
  
CTC Collection for 
Evaluation of HER2 
Expression** 
x 
  
  
  
  
x 
Trastuzumab Dispensing 
  
  
X 
x 
  
  
Clinical Safety Assessment 
  
  
  
  
  
  

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Physical exam 
  
x 
x 
x 
x 
x 
Vital signs, body 
weight and ECOG 
  
x 
x 
x 
x 
x 
Signs and symptoms 
assessment 
  
x 
x 
x 
x 
x 
Review of 
medications in 
use 
  
x 
x 
x 
x 
x 
Adverse Event Assessment 
  
  
x 
x 
x 
x 
Laboratory safety 
assessment 
  
  
  
  
  
  
HMG, Ur, Cr, Na , K 
x 
  
X 
X 
  
  
Ecocardiogram*** 
x 
  
  
X 
  
  
Image assessment 
  
  
  
  
  
  
CT of lung, abdomen and 
pelvis or MRI**** 
x 
  
  
X 
  
x 
* within 48h of D1C1 
**at least 7 days before D1C1 
*** Ecocardiogram: the first within 10 days of D1C1 and should be requested every 3 months during treatment 
**** Within 4 weeks of D1C1 and every 4 cycles (± 5 days) 
 
Funding 
This is an academic and initiative study of the main investigator (Rachel P 
Riechelmann). There will be no cost to the patient in relation to the research procedures, 
such as blood collection for CTC evaluation and trastuzumab drug. The cost of conducting 
the test will be through a research grant provided by the brazilian company Libbs. In the 
case of CTC-positive HER2 patients and therefore with indication for trastuzumab combined 
with chemotherapy, Libbs will donate commercially available biosimilar trastuzumab in the 

Version 2 November 2019 
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brazilian market and standard AC Camargo for treatment until disease progression, 
unacceptable toxicity or withdrawal of consent. The company will only have access to the 
final result of the work and will not participate in the study design, or in any phase of its 
execution, as well as not have access to the individual data of patients included in this 
project. Research grant money donated by Libbs includes funding for insurance to cover 
potential damages associated with research and coverage for treatment of adverse events 
associated with trastuzumab. The patient's paying source pays for routine treatment: 
chemotherapy, blood tests and imaging, as is already done in the treatment routine of these 
patients. Echocardiography is warranted as a routine test for HER2-positive gastric cancer 
patients because the trastuzumab package insert in Brazil describes that this medication is 
indicated for first-line advanced HER2-positive gastric cancer without specifying by which 
diagnostic test the HER2 result was obtained. 
  
Ethical Considerations 
The study will be conducted in accordance with the International Harmonization 
Conference protocol of Good Clinical Practice guidelines (ICH GCP), and applicable local laws 
and regulatory requirements. The Informed Consent Form (ICF) must comply with ICH GCP 
guidelines, local regulatory regulations, and legal requirements. 
The investigator should ensure that each study patient, or legal representative, is 
fully informed about the nature and objectives of the study and possible risks associated 
with participation. The investigator will obtain written consent from each patient before 
any specific study activity is performed. The investigator will retain one copy of each 
consent form signed by the patient. It will be emphasized that participation is voluntary and 
that the patient has the right to refuse participation or leave in the middle of the study at 
any time. This will not impair subsequent patient care. There is a risk of loss of 
confidentiality if patient data is identified, however, all reasonable measures will be taken 
to prevent this from occurring, such as: database without participant identifying 
information, password protected database and only by study investigators. 

Version 2 November 2019 
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This is an academic and initiative study of the principal investigator (Rachel P 
Riechelmann). The Libbs company that will have access only to the final result of the work 
and will not participate in the study design or in any phase of its accomplishment, as well 
as not have access to the individual data of the patients included in this project. 
The protocol was approved by the Local Ethics Committee. 
  
 
 
 
 
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Cancer J Clin. 2011;61(2):69-90. 
2. World Health Organization. International Agency for Research on Cancer. 
GLOBOCAN 2018: stomach cancer fact sheet. 2018. 
3. Torre LA, Bray F, Siegel RL, Ferlay J, Lortet-Tieulent J and Jemal A. Global cancer 
statistics, 2012. CA Cancer J Clin. 2015;65(2):87-108. 
4. Estatísticas 
de 
câncer. 
INCA, 
Jun/2019. 
Disponível 
em 
https://www.inca.gov.br/numeros-de-cancer 
5. Van Cutsem E, Bang YJ, Feng-Yi F, Xu JM, Lee KW, et al. HER2 screening data from 
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