• Age ≥ 18 years.

• Completion of surgical and peri-operative treatments as per international guidelines.

• 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.

• Subject must not have standard treatment at least 3 weeks before blood sampling for ctDNA analyses.

• Patients must not have blood transfusion at least 3 months before blood sampling for ctDNA analyses.

• 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.

• 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.

• Subjects must have a valid (positive or negative) ctDNA test result prior to randomization.

• Subjects must not have had prior immunotherapy (anti-PD-1 or anti-PD-L1).

⁃ No evidence of disease on imaging as per RECIST criteria 1.1.

⁃ Eastern Cooperative Oncology Group (ECOG) Performance Status 0 or 1.

⁃ Subjects must have adequate organ function as indicated by the following laboratory values (obtained within 7 days prior to randomization):

∙ 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.

‣ International normalized ratio (INR) or prothrombin time (PT) ≤ 1.5 x upper limit of normal (ULN).

‣ Activated partial thromboplastin time (aPTT) ≤ 1.5 x ULN.

‣ Serum total bilirubin ≤ 1.5 x ULN (total bilirubin must be \< 3 x ULN for patients with Gilbert's syndrome).

‣ Aspartate and alanine aminotransferase (AST and ALT) ≤ 3 x ULN.

‣ 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).

⁃ Subjects with a social security in compliance with the French law relating to biomedical research (Article L.1121-11 of French Public Health Code).

⁃ 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.

⁃ 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).

⁃ 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.