tislelizUMaB in canceR Patients With molEcuLar residuaL Disease

Inclusion Criteria: 1. Age ≥ 18 years. 2. Completion of surgical and peri-operative treatments as per international guidelines. 3. Subject must have completed standard curative-intent therapy (i.e: Surgery, Neoadjuvant and adjuvant therapy) for minimum 3 months and maximum 4.5 months prior to sending samples for MRD analyses. 4. Subject must not have standard treatment at least 3 weeks before blood sampling for ctDNA analyses. 5. Patients must not have blood transfusion at least 3 months before blood sampling for ctDNA analyses. 6. Histology: TNM stage II-III NSCLC, Stage II-III colorectal cancer, stage I-III pancreatic cancer, grade 3 limb or trunk wall soft-tissue sarcoma. 7. Subjects must have sufficient amount of archived primary tumor material for ctDNA and translational research analyses that will be conducted as defined in the protocol. 8. Subjects must have a valid (positive or negative) ctDNA test result prior to randomization. 9. Subjects must not have had prior immunotherapy (anti-PD-1 or anti-PD-L1). 10. No evidence of disease on imaging as per RECIST criteria 1.1. 11. Eastern Cooperative Oncology Group (ECOG) Performance Status 0 or 1. 12. Subjects must have adequate organ function as indicated by the following laboratory values (obtained within 7 days prior to randomization): 1. Absolute neutrophil count (ANC) ≥ 1.5 x 109/L, platelets ≥ 100 x 109/L, haemoglobin ≥90 g/L. Note: Patients must not have required growth factor support ≤ 14 days before sample collection. 2. International normalized ratio (INR) or prothrombin time (PT) ≤ 1.5 x upper limit of normal (ULN). 3. Activated partial thromboplastin time (aPTT) ≤ 1.5 x ULN. 4. Serum total bilirubin ≤ 1.5 x ULN (total bilirubin must be \< 3 x ULN for patients with Gilbert's syndrome). 5. Aspartate and alanine aminotransferase (AST and ALT) ≤ 3 x ULN. 6. Creatinine clearance ≥60 mL/min for participants with creatinine levels above institutional normal (≥ULN). Creatinine clearance should be calculated per the Cockcroft-Gault formula (or local institutional standard method). 13. Subjects with a social security in compliance with the French law relating to biomedical research (Article L.1121-11 of French Public Health Code). 14. Subjects should understand, sign, and date the written informed consent form prior to any protocol-specific procedures performed. Patient should be able and willing to comply with study visits and procedures as per protocol. 15. Females of childbearing potential must be willing to use a highly effective method of birth control for the duration of the trial, and ≥ 120 days after the last dose of the trial drug and have a negative serum pregnancy test ≤ 7 days of the first dose of the trial drug. A barrier contraceptive method (e.g., condom) is also required. A woman is considered of childbearing potential following menarche and until becoming post-menopausal (≥ 12 months of non-therapy-induced amenorrhea) unless permanently sterile. Permanent sterilization methods include hysterectomy, bilateral oophorectomy and bilateral salpingectomy with surgery at least 1 month before the first dose of study drug or confirmed by follicle stimulating hormone (FSH) test \>40 mIU/mL and estradiol \<40 pg/mL (\<140 pmol/L). 16. Nonsterile males must be willing to use a highly effective method of birth control for the duration of the study and for ≥ 120 days after the last dose of the trial drug. A barrier contraceptive method (e.g., condom) is also required. Exclusion Criteria: 1. Participation in another clinical trial with an investigational product during the last 3 to 4.5 months and while on study treatment 2. Any condition which in the Investigator's opinion makes it undesirable for the subject to participate in a clinical trial or which would jeopardize compliance with the protocol, 3. Pregnant or breastfeeding women 4. Subjects under guardianship or deprived of his liberty by a judicial or administrative decision or incapable of giving its consent. 5. Patients with confirmed EGFR (Epidermal Growth Factor Receptor ) exon 19 deletions or exon 21 L858R substitutions are excluded from the study, due to the potential benefit from adjuvant osimertinib treatment, which represents a standard of care for these genetic profiles in non-small cell lung cancer (NSCLC). 6. Treatment with systemic immunostimulatory agents (including but not limited to interferons or interleukin-2) within 4 weeks or five half-lives of the drug, whichever is shorter, prior to enrolment 7. Treatment with systemic immunosuppressive medication (including, but not limited to, corticosteroids, cyclophosphamide, azathioprine, methotrexate and thalidomide) within 2 weeks prior to initiation of study treatment, or anticipation of need for systemic immunosuppressive medication during study treatment, with the following exceptions: * Patients who received acute, low-dose systemic immunosuppressant medication or a one-time pulse dose of systemic immunosuppressant medication (e.g., 48 hours of corticosteroids as premedication for hypersensitivity reaction (e.g., CT scan premedication)) are eligible for the study after Principal investigator approval has been obtained * Patients who received mineralocorticoids (e.g., fludrocortisone), corticosteroids for chronic obstructive pulmonary disease (COPD) or asthma, or low-dose corticosteroids for orthostatic hypotension or adrenal insufficiency are eligible for the study * Patients who received intranasal, inhaled, topical or local steroid injections (e.g., intra articular injection) 8. Any prior Grade ≥3 immune-related adverse event (irAE) while receiving any previous immunotherapy agent, or any unresolved irAE \> Grade 1. 9. Known intolerance the study drugs or any of their excipients 10. Patients with prior allogeneic stem cell or solid organ transplantation 11. Administration of a live, attenuated vaccine within 4 weeks prior to enrolment or anticipation that such a live, attenuated vaccine will be required during the study or within 5 months after the last dose of the study drugs (except anti-COVID-19 vaccines) 12. Active or history of autoimmune disease or immune deficiency, with the exception of history of treated autoimmune-related hypothyroidism and Type 1 diabetes mellitus on insulin regimen 13. History of idiopathic pulmonary fibrosis (including pneumonitis or interstitial lung disease), drug-induced pneumonitis, organizing pneumonia (i.e. bronchiolitis obliterans, cryptogenic organizing pneumonia), or evidence of active pneumonitis (history of radiation pneumonitis in the radiation field (fibrosis) is permitted). 14. Patients who underwent major surgery within 56 days prior to inclusion or until the surgical wound is fully healed 15. History of HIV infection 16. Patients with active hepatitis infection (defined as having a positive hepatitis B surface antigen \[HBsAg\] test at screening) or hepatitis C. Patients with past hepatitis B virus (HBV) infection or resolved HBV infection (defined as having a negative HBsAg test and a positive antibody to hepatitis B core antigen \[anti-HBc\] antibody test) are eligible. Patients positive for hepatitis C virus (HCV) antibody are eligible only if polymerase chain reaction (PCR) is negative for HCV RNA 17. Active tuberculosis. 18. History of severe allergic, anaphylactic, or other hypersensitivity reactions to chimeric or humanized antibodies or fusion proteins 19. Severe infection within 4 weeks prior to initiation of study treatment, including, but not limited to, hospitalization for complications of infection, bacteremia, or severe pneumonia 20. Treatment with therapeutic oral or IV antibiotics within 2 weeks prior to initiation of study treatment 21. Significant cardiovascular disease, such as: * History of myocardial infarction, acute coronary syndromes or coronary angioplasty/stenting/bypass grafting within the past 6 months, * Congestive Heart Failure (CHF) NYHA class III or IV or history of CHF NYHA class III or IV, unless an echocardiogram or multi-gated acquisition scan performed within 3 months day 1 reveals a left ventricular ejection fraction ≥ 55% 22. Uncontrolled hypertension defined by systolic pressure \> 150 and/or diastolic pressure \> 110 mmHg, with or without anti-hypertensive medication. Patients with initial blood pressure elevations are eligible if initiation or adjustment of anti-hypertensive medication lowers blood pressure to meet entry criteria 23. History of stroke or transient ischemic attack within 6 months prior to randomization