Inclusion Criteria:

          1. Male or female subjects aged ≥18 years

          2. ECOG PS 0/1

          3. Histologically proven, stage III (i.e., any T, N1 or N2, M0) adenocarcinoma of the
             colon (as defined by the presence of the inferior pole of the tumour above the
             peritoneal reflection - that is, at least 15 cm from the anal margin).

          4. Fully surgically resected tumour with clear resection margins (i.e., >1 mm)

          5. Locally confirmed defective mismatch repair (dMMR) tumour (as defined by the lack of
             staining on either the pre-operative biopsy samples or resection specimens of at least
             one of the following proteins: MLH1 (mutL homolog 1), MSH2 (mutS homologue 2), MSH6
             (mutS homolog 6), PMS2 or centrally confirmed POLE exonuclease domain mutated tumour
             (in subjects <50 years old with pMMR tumours)

          6. Absence of metastases as shown by post-operative CT scan

          7. Absence of major post-operative complications or other clinical conditions that, in
             the opinion of the investigator, would contraindicate adjuvant chemotherapy 8.
             Adequate hematological function defined by absolute neutrophil count (ANC) ≥1.5 ×
             109/L, platelet count ≥100 × 109/L, and hemoglobin ≥9 g/dL (blood transfusion before
             recruitment is allowed)

        9. Adequate hepatic function defined by a total bilirubin level ≤1.5 × the upper limit of
        normal (ULN) range and AST and ALT levels ≤2.5 × ULN 10. Adequate renal function defined by
        an estimated creatinine clearance ≥30 mL/min according to the Cockcroft-Gault formula (or
        local institutional standard method) 11. Negative serum or urine pregnancy test at
        screening for women of childbearing potential 12. Fertile men and women must agree to take
        highly effective contraceptive precautions during, and for 6 months after the last dose of
        chemotherapy or for 1 month after the last dose of Avelumab

        Exclusion Criteria:

          1. Rectal tumours (as defined by the presence of the inferior pole of the tumour below
             the peritoneal reflection - that is, <15 cm from the anal margin).

          2. Inability to start adjuvant chemotherapy within 12 weeks after surgery

          3. Administration of neoadjuvant systemic chemotherapy or radiotherapy before surgical
             resection of colon cancer

          4. Prior organ transplantation, including allogeneic stem-cell transplantation

          5. Significant acute or chronic infections including, among others:

               -  known history of testing positive test for human immunodeficiency virus (HIV) or
                  known acquired immunodeficiency syndrome (AIDS)

               -  positive test for HBV (Hepatitis B) surface antigen or anti-HCV (Hepatitis C)
                  antibody and confirmatory HCV RNA test

          6. Active autoimmune disease that might deteriorate when receiving an immunostimulatory
             agent:

               -  Subjects with diabetes type I, vitiligo, psoriasis, hypo- or hyperthyroid disease
                  not requiring immunosuppressive treatment are eligible

               -  Subjects requiring hormone replacement with corticosteroids are eligible if the
                  steroids are administered only for the purpose of hormonal replacement and at
                  doses ≤10 mg/day of prednisone or equivalent

               -  Administration of steroids through a route known to result in a minimal systemic
                  exposure (topical, intranasal, intro-ocular, or inhalation) are acceptable

          7. Known severe hypersensitivity reactions to monoclonal antibodies (Grade ≥3 NCI-CTCAE
             v4.0), any history of anaphylaxis, or uncontrolled asthma (that is, 3 or more features
             of partially controlled asthma)

          8. Persisting toxicity related to prior therapy of Grade >1 NCI-CTCAE v4.0; however,
             alopecia and sensory neuropathy Grade ≤2 is acceptable unless oxaliplatin
             administration is planned as part of the adjuvant treatment

          9. Pregnancy or lactation

         10. Known alcohol or drug abuse

         11. Clinically significant (i.e., active) cardiovascular disease: cerebral vascular
             accident/stroke (<6 months prior to enrollment), myocardial infarction (<6 months
             prior to enrollment), unstable angina, congestive heart failure (≥ New York Heart
             Association Classification Class II), or serious cardiac arrhythmia requiring
             medication

         12. Known history of colitis, pneumonitis and pulmonary fibrosis (for example,
             inflammatory bowel disease, uncontrolled asthma), which, in the opinion of the
             Investigator, might impair the subject's tolerance of trial treatment.

         13. Any psychiatric condition that would prohibit the understanding or rendering of
             informed consent

         14. Vaccination within 4 weeks of the first dose of Avelumab and while on trial is
             prohibited except for administration of inactivated vaccines

         15. Other invasive malignancy within 2 years except for non-invasive malignancies such as
             cervical carcinoma in situ, non-melanomatous carcinoma of the skin or ductal carcinoma
             in situ of the breast that has/have been surgically cured. Cancer subjects with
             incidental histological findings of prostate cancer (tumour/node/metastasis stage of
             T1a or T1b or prostate-specific antigen ˂10) who have not received hormonal treatment
             may be included, pending a discussion with the study physician.

             -