18FDG PET for Early Identification of Tumor Exhaust for Immunotherapy in Patients With Locally Advanced or Metastatic Non-Small Cell Bronchopulmonary Carcinoma or Melanoma

Inclusion Criteria: * Age \> or = 18 years, * Patients with unresectable melanoma or histologically proven, metastatic or locally advanced NSCLC, * Indication of an immunotherapy treatment with nivolumab or pembrolizumab validated in multidisciplinary consultation team and prescribed as part of their marketing authorization, in first or second line of treatment, * Performance Status 0 to 2, * Female subjects of childbearing potential should have a negative urine or serum pregnancy within 72 hours prior to receiving the first dose of study medication. If the urine test is positive or cannot be confirmed as negative, a serum pregnancy test will be required, * Female subjects of childbearing potential should be willing to use 2 methods of birth control or be surgically sterile, or abstain from heterosexual activity for the course of the study through 6 months after the last dose of study medication. Subjects of childbearing potential are those who have not been surgically sterilized or have not been free from menses for \> 1 year, * Male subjects should agree to use an adequate method of contraception or abstain from heterosexual activity starting with the first dose of study therapy through 6 months after the last dose of study therapy, * Patient willing and able to provide written informed consent/assent for the trial, * Patient affiliated with a health insurance system. Exclusion Criteria: * Age \< 18 years, * Contraindication to performing 18FDG PET scans: severe claustrophobia, unbalanced diabetes during PET examinations (fasting capillary blood glucose ≥ 11 mmol), * Any participation in other biomedical studies related to the drug, medical devices or imaging techniques is prohibited except biomedical studies called overstudies (In case of doubt or questions about the patient's participation in a other clinical study, please contact the sponsor), * Contraindication to nivolumab or pembrolizumab treatment, * Patient with metastatic disease, * History of thoracic irradiation or near / in the thoracic irradiation field, * Patient who refuses to participate in the study or unable to agree, * Patient currently receiving one or more treatments described in section 6.9 of the protocol, * Contraindication to nivolumab or pembrolizumab treatment, * People particularly vulnerable as defined in Articles L.1121-5 to -8 of the French Healthcare Code, including: person deprived of freedom by an administrative or judicial decision, adult being the object of a legal protection measure or outside a state to express their consent, pregnant or breastfeeding women.