Table 1 Eligibility criteria for the study population

1. Patient must have signed a written informed consent form prior to any trial specific procedures

2. Patient aged ≥ 18 years old

3. Initial metastatic disease histologically confirmed including: lung cancer, renal cell cancer, head and neck cancer, bladder cancer, triple negative breast cancer, Merkel cancer, hepatocellular carcinoma, melanoma, colorectal carcinoma with microsatellite instability [MSI], or esophageal squamous cell carcinoma

4. Patients in partial or complete response after 6 months of standard immunotherapy (whatever the line of therapy) according to the RECIST criteria (confirmed by local radiological assessment). For metastatic melanoma only patients in partial response

5. Eligible to maintain the same standard IO treatment

6. Patient with ECOG performance status ≤ 1

7. Patients with brain metastases are allowed, provided they are stable according to the following definitions: treated with surgery or stereotactic radiosurgery and without evidence of progression prior to randomization and have no evidence of new or enlarging brain metastases

8. Patients treated by IO previously combined with chemotherapy are allowed

9. Patients with TKI-IO or pemetrexed-IO or bevacizumab-IO are allowed

10. Evidence of post-menopausal status, negative urinary, or serum pregnancy test for female pre-menopausal patients

11. Both sexually active women of childbearing potential and males (and their female partners) patients must agree to use adequate contraception method for the duration of the study treatment and after completing treatment according to the most recent version of the IO SmPC

12. Patient is willing and able to comply with the protocol for the duration of the trial including undergoing treatment and scheduled visits, and examinations including follow-up

13. Patient must be affiliated to a Social Security System

1. Metastatic melanoma in complete response

2. Metastatic renal cell carcinoma with IMDC favourable-risk treated TKI/IO combination

3. Hematologic malignancies (leukaemia, myeloma, lymphoma…)

4. Active infection requiring systemic therapy

5. Patients enrolled in another therapeutic study within 30 days before the inclusion in and during MOIO study

6. Patient unable to comply with study obligations for geographic, social, or physical reasons, or who is unable to understand the purpose and procedures of the study

7. Person deprived of their liberty or under protective custody or guardianship