⁃ I1. Male or female patients aged ≥ 18 years old at time of inform consent signature.

⁃ I2. Patients with primary head and neck tumour up to, but not crossing the midline, previously untreated with histologically-confirmed squamous cell carcinoma of:

• the oropharynx p16-, larynx or hypopharynx : T1/N2a-N2b, T2/N0-N2b, T3/N0-N2b (UICC 8th Ed.), or

• the oropharynx p16+ : T1/N1 (multiple nodes), T2-T3/N0-N1 (UICC 8th Ed.).

⁃ I3. Patients with lymph node staging assessed by an FDG-PET/CT with no contralateral nodal uptake.

⁃ I4. Patients amenable to treatment with RT or concomitant chemo-radiotherapy as decided by the treating physician as a function of tumor stage, tumor location, performance of the patients.

⁃ I5. Eastern Cooperative Oncology Group (ECOG) Performance Status 0 or 1.

⁃ I6. Adequate hematologic and end-organ function, defined by the following laboratory test results obtained within 7 days prior to randomisation :

⁃ Hematological (without transfusion within 2 weeks) :

• Neutrophils count \> 1.5 × 109 /L

• Platelets count \> 75 × 109 /L

• WBC≥ 3.0 × 109 /L

⁃ Hepatic function :

• Total Bilirubin \< 1.5 × ULN (except for Gilbert's syndrome which will allow bilirubin ≤ 3 ULN).

• Alanine aminotransferase (ALT) ≤ 2.5 × ULN.

• Aspartate aminotransferase (AST) ≤ 2.5 × ULN.

• Albumin \>3.0g/dL

⁃ Renal function :

• Serum creatinine \< 1.5 ×ULN.

⁃ I7. QTcF ≤450ms for men and 470ms for women, from 3 electrocardiograms on screening ECG, within 7 days prior randomisation.

⁃ I8. Women patients of child-bearing potential are eligible, provided they have a negative serum or urine pregnancy test within 7 days prior randomisation, and agrees to use adequate contraception for up to 1 month after the end of study treatments.

⁃ I9. Fertile men must agree to use an effective method of contraception during the study and for up to 1 month after the end of study treatments.

⁃ I10. Patient should understand, sign, and date the written voluntary informed consent form prior to any protocol-specific procedures performed and should be able and willing to comply with study visits and procedures as per protocol.

⁃ I11. Patients must be covered by a medical insurance in country where applicable.