Phase I Trial of CArbonic Anhydrase Inhibition in Combination With Radiochemotherapy or Radioimmunotherapy in Small Cell Lung Carcinoma

Inclusion Criteria: * Age \> or = 18 years, * Performance Status 0 to 2, * Patient with an histologically non-metastatic localized (or extensive SCLC sub-group) Small cell lung cancer, * Patient who must start radiotherapy treatment combined with chemotherapy with platinum and etoposide (localized SCLC sub-group) or Patient who received 4 cycles of chemoimmunotherapy with platinum salts, etoposide and immunotherapy (atezolizumab or durvalumab) as the first treatment (extensive SCLC sub-group) Note: The decision of the Multidisciplinary Consultation Team must be notified in the patient's medical file, * Evaluation lesion according to the criteria RECIST 1.1 and / or according to the criteria PERCIST 1.0, * Women of childbearing potential must have a negative serum pregnancy test within 72 hours of the first administration of the study treatment, * If the patient is a woman of childbearing potential, she must be surgically sterile or agree to use two adequate methods of contraception throughout the duration of the study until 1 month after the last administration of the study treatment. Subjects of childbearing potential are those who have not been surgically sterilized or have not been free from menses for \> 1 year, Note: Abstinence is acceptable if it is the patient's usual and preferred form of contraception, * If the male patient has one or more female partners of childbearing age, he / she must agree to use an adequate method of contraception, starting at the first administration of the study treatment up to 1 month after the last administration of the treatment. of the study, Note: Abstinence is acceptable if it is the patient's usual and preferred form of contraception, * Patient willing and able to provide written informed consent/assent for the trial, * Patient affiliated with a health insurance system. Exclusion Criteria: * 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, * Contraindication to thoracic radiotherapy treatment: congestive heart failure unbalanced (ejection fraction \<30%, clinical signs), severe respiratory failure: * COPD grade IV according to the GOLD classification, * Some GOLD III COPD and any patient with a respiratory defect defined as: oxygen dependence and / or FEV1 \<40% normal and / or, DLCO \<40% predictive value and / or vital capacity \<40% predictive value, * Contraindication to acetazolamide: hypersensitivity to acetazolamide, severe hepatic, renal or adrenal insufficiency, sulfonamide intolerance, history of renal colic, allergy to wheat other than celiac disease, * Patient currently receiving one or more treatments described in section 6.9 of the protocol, * History of cancer, with the exception of cancers in complete remission for more than 5 years, completely resected basal cell carcinoma of the skin or squamous cell carcinoma of the skin that has undergone potentially curative therapy or in situ cervical cancer, * 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