Adaptative Radiotherapy to Decrease Xerostomia in Oropharynx Carcinoma

Inclusion Criteria: 1. Locally advanced non-metastatic carcinoma of the oropharynx limited to T3 and T4 (whatever the N) and N2-N3 (whatever the T)(AJCC stage III-IV) 2. Age ≥ 18 years and ≤ 75 years 3. Performance status (WHO ≤ 2) 4. Renal, hepatic and cardiovascular functions allowing systemic treatment administration 5. Adapted stomatologic care 6. Signed informed consent form 7. Membership or beneficiary of a national insurance scheme Exclusion Criteria: 1. Both parotids totally included in the target volume 2. Stages T1 or T2 with positive node disease N1 3. Neoadjuvant chemotherapy 4. Exereses of primitive tumor and/or nodes 5. History of other cancer within 5 years (except for basocellular epithelioma and cervical) 6. Previous neck radiotherapy 7. Platinum salts, 5FluoroUracile (5FU) agents or cetuximab chemotherapy considerations 8. Unstable diseases (cardiovascular, renal, pulmonary, systemic lupus or sclerodermia)incompatible with study participation 9. Patient participating in other therapeutic trial with experimental drug, 30 days before the inclusion. 10. Patient already recruited in another biomedical research ( non interventional study is authorized) 11. Pregnant or breast feeding patients 12. Patient deprived of liberty, under tutorship, guardianship or placed under judicial protection 13. Patient is deemed incapable of giving informed consent 14. Patients who, for family, social, geographic or psychological reasons, cannot be adequately followed up and/or are incapable of undergoing regular controls.