STEREO-POSTOP 01 (PostOperative Hypofractionated Stereotactic Body Radiotherapy ) - GORTEC 2017-03

Inclusion Criteria: * Operated squamous cell carcinoma of oral cavity (lips excepted) or oropharynx * pT1 or pT2 ((UICC 7th edition 2009) * Indication of postoperative tumor site irradiation (retained in multidisciplinary tumor board) with at least one of the following criteria : * positive R1 margin (re-resection not proposed) * close margin \< 5 mm (re-resection not proposed) * Margin estimated at risk, with uncertain pathological margin (re-resection not proposed) * N0 after surgical management of the neck (neck dissection or sentinel lymph node biopsy) or pN1 without extracapsular extension (carcinological neck dissection) * Age ≥ 18 years * ECOG status ≤ 2 * Written signed informed consent before any specific procedure of the protocol * Affiliation to a social security scheme or beneficiary of such a scheme Exclusion Criteria: * Other histology than squamous cell carcinoma * pT3 or pT4 * pT2\>3cm and R1 with concurrent chemoradiotherapy decided in multidisciplinary tumor board * Lymphovascular invasion justifying neck irradiation * Neck irradiation decided in multidisciplinary tumor board * Lack of at least one of the following elements : * pre-operative medical imaging (CT scan or MRI) * endoscopy report * surgery report * pathological report * Prior radiotherapy to the head and neck area * Distant metastasis * Pregnant or nursing (lactating) woman * women or men of childbearing age not taking adequate contraceptive measure * participation in another investigational study within 4 weeks prior to inclusion * History of other malignancy within 5 years prior enrollment except for basal cell carcinoma of the skin or carcinoma in situ of the cervix * Persons deprived of their liberty, under guardianship or curatorship, or unable to follow the trial for geographical, social or psychological reasons