Circulating Tumor DNA MRD-Guided Adjuvant Therapy for Curatively Resected Locally Advanced Esophageal Squamous Cell Carcinoma

Inclusion Criteria:

• 1. Be willing and able to provide written informed consent. 2. Be ≥19 years of ageon the day of signing the informed consent form. 3. Have ECOG performance status of 0 or 1 (Appendix 1). 4. Have a histologically confirmed diagnosis of squamous cellcarcinoma of the esophagus

• Patients with tumors of mixed histology (i.e., squamous and non-squamous) areeligible if the predominant histological component is squamous, except whensmall cell or neuroendocrine elements are present.

5. Must have completed surgical resection for localized disease, either withprior neoadjuvant chemoradiotherapy or without prior neoadjuvant therapy (i.e.,upfront surgery), in accordance with the 8th edition of the AJCC staging system (Appendix 2). Exceptionally, cases with supraclavicular lymph node metastasisas the only M1 lesion are also eligible if the lymph node has been surgicallyremoved.
6. Must have undergone curative surgery (R0 resection) with negative margins onthe resected specimen.
7. Complete resection must have been performed within 4-16 weeks beforerandomization.
8. Must have a documented disease-free status based on a complete physicalexamination and imaging studies within 4 weeks before randomization. Imagingstudies must include CT scans (or MRI) of the chest, abdomen, and pelvis.
9. Must provide tumor tissue from pre-treatment biopsy (i.e., a biopsy obtainedprior to neoadjuvant therapy in cases where neoadjuvant therapy is followed bysurgery) or from surgical specimens and baseline blood samples for post-surgeryctDNA-MRD measurement and biomarker analyses.

• For patients who underwent upfront surgery, surgical tissue is preferred. Forthose who received neoadjuvant therapy followed by surgery, pre-treatmentbiopsy tissue is preferred.

• A FFPE tumor specimen in a paraffin block or 20 (at least 10, with a thicknessof 10 µm) freshly cut unstained FFPE slides, along with one H&E-stained slidewith tumor-area marking, must be submitted with the associated pathologyreport. If an insufficient number of slides is available, the decision onpatient enrollment can be made in consultation with the Study Sponsor.

• Peripheral blood of 20 mL must be collected between 3 to 12 weeks aftercurative surgery for ctDNA testing.

10. Must be confirmed to have MRD-positive status via postoperative baselinectDNA testing.
11. Must have adequate major organ functions as demonstrated by the followinglaboratory results obtained within 14 days before randomization (these criteriamust also be met within 7 days before initiating study treatment in theadjuvant therapy arm):

• Adequate bone marrow function defined by:

• Absolute neutrophil count (ANC) ≥ 1,500/μL without granulocyte colony-stimulatingfactor support within 7 days before laboratory testing

• Platelet count ≥ 100 ×103/μL without transfusion within 7 days before laboratorytesting • Adequate renal function defined by:

• Serum creatinine ≤ 1.5 × upper limit of normal (ULN) or creatinine clearance (CrCl) ≥ 50 mL/minute, calculated using the Cockcroft-Gault formula (Appendix 3) ormeasured by a 24-hour urine collection

• Adequate hepatic function defined by:

• ALT and AST ≤ 2.5 × ULN

• Total bilirubin ≤ 1.5 × ULN, except for subjects with Gilbert syndrome (persistentor recurrent hyperbilirubinemia that is predominantly unconjugated in the absence ofhemolysis or hepatic pathology), who must have a total bilirubin level ≤ 3 × ULN 12.Female subjects of childbearing potential must have a negative urine or serumpregnancy test within 14 days prior to randomization. If the urine test is positiveor inconclusive, a serum pregnancy test will be required.

13. Female subjects of childbearing potential randomized to the adjuvant therapy armmust agree to use an adequate method of contraception for the duration of studytreatment and for 90 days after the last dose of study treatment.

14. Non-sterile male subjects randomized to the adjuvant therapy arm with femalesexual partner(s) of childbearing potential must agree to use an adequate method ofcontraception for the duration of study treatment and for 90 days after the lastdose of study treatment.

Exclusion Criteria:

• 1. Documented recurrence of esophageal cancer before randomization followingcurative resection.

2. Receipt of any treatment aimed at the resected esophageal cancer after curativesurgery, including chemotherapy, targeted therapy, immunotherapy, radiotherapy,biologic therapy, investigational agent, or local therapies, except for proceduresintended for palliative care (e.g., stent insertion, balloon dilatation, or feedingenterostomy).

3. Prior therapy with an anti-PD-1, anti-PD-L1, anti-PD-L2, or anti-cytotoxicT-lymphocyte-associated antigen-4 (CTLA-4) inhibitor, or any other drug targetingT-cell co-stimulation or checkpoint pathways.

4. Active autoimmune disease requiring systemic treatment within the 2 years priorto study entry (i.e., using disease-modifying agents, corticosteroids, orimmunosuppressive drugs).

• Replacement therapy (e.g., thyroxine for autoimmune-related hypothyroidism,insulin for type 1 diabetes mellitus, or physiologic corticosteroid replacementtherapy for adrenal or pituitary insufficiency) is not considered a form of systemictreatment and is allowed.

5. Condition requiring systemic treatment with corticosteroids (>10 mg dailyprednisone or equivalent) or any other form of immunosuppressive therapy within 14days prior to study entry.

• Use of topical, ocular, intra-articular, intranasal, and inhaled corticosteroidsis permitted if there is no active autoimmune disease.

• A short course of corticosteroids for prophylaxis (e.g., contrast dye allergy)or treatment of non-autoimmune conditions (e.g., delayed-type hypersensitivityreaction caused by contact allergens) is permitted.

6. Receipt of a live vaccine within 28 days prior to study entry.

• COVID-19 vaccines are allowed except for any live vaccine. Seasonal influenzavaccines for injection are generally killed virus vaccines and are allowed;however, intranasal influenza vaccines (e.g., FluMist®) are live attenuatedvaccines and are not allowed.

7. Active infection requiring systemic therapy within 14 days prior to studyentry.
8. History of severe hypersensitivity to paclitaxel, carboplatin, or anyantibody products.
9. Known history of, or any evidence of, interstitial lung disease,non-infectious pneumonitis, or pulmonary fibrosis diagnosed based on imaging orclinical findings.

• Subjects with radiation pneumonitis may be enrolled if radiation pneumonitis isstable (beyond the acute phase) and unlikely to recur.

10. History of allogeneic stem cell or solid organ transplantation. 11.Malignancies other than esophageal cancer within the 3 years prior to studyentry, except for malignancies with a negligible risk of metastasis or death (e.g., 5-year OS rate >90%), such as adequately treated non-melanoma skincancer, superficial bladder cancer, or carcinoma in situ (e.g., cervix, breast,or prostate).

• Subjects who received endoscopic mucosal resection or dissection forsuperficial mucosal cancers within the past 3 years are eligible.

12. Subjects with toxicities attributed to prior anti-cancer therapy, exceptalopecia, anorexia, fatigue, and hearing loss, that have not resolved to Grade 1 (NCI CTCAE v5.0) or baseline before randomization will be excluded.
13. Significant cardiovascular impairment within 6 months prior to study entry,including a history of congestive heart failure (New York Heart AssociationClass III or IV), unstable angina, myocardial infarction, cerebrovascularaccident, or cardiac arrhythmia associated with hemodynamic instability.
14. Any serious or uncontrolled medical disorder that, in the investigator'sopinion, may increase the risk associated with study participation or studytreatment administration, or compromise the subject's ability to receiveprotocol therapy.
15. History or current evidence of any condition, therapy, or laboratoryabnormality that could confound trial results, interfere with the subject'sparticipation for the full trial duration, or is not in the best interest ofthe subject to participate, in the investigator's opinion.
16. Medical or psychiatric conditions that impair the subject's ability to giveinformed consent or complete the protocol, or a history of non-compliance.
17. Known history of Human Immunodeficiency Virus (HIV) infection. 18.Untreated chronic hepatitis B or chronic hepatitis B virus (HBV) carriers withHBV DNA ≥500 IU/mL (or 2,500 copies/mL), or active hepatitis C virus (HCV)infection:

• Subjects with chronic hepatitis B (HBV DNA < 500 IU/mL or < 2,500 copies/mL)who are receiving antiviral therapy can be enrolled. Patients with detectableHBsAg or detectable HBV DNA should be managed according to institutionalguidelines.

• Patients with a negative HCV antibody test result at screening or a positiveHCV antibody test followed by a negative HCV RNA test result at screening areeligible.

19. Pregnant or breastfeeding women 20. Any condition requiring treatment withprohibited or restricted concomitant medication or therapy as described inSection 6.2.2