De-escalation of Adjuvant Radio (Chemo) Therapy for HPV-positive Head-neck Squamous Cell Carcinomas

Inclusion Criteria: * Condition after surgical removal of a squamous cell carcinoma of the oropharynx and adequate lymph node dissection * Indication for adjuvant radiotherapy or radiochemotherapy in the interdisciplinary tumor board * Good general state (ECOG performance status 0 or 1) * Adequate compliance to ensure closely follow-up * Patient's consent and written consent * Neck dissection of at least the tumor bearing side Additional Inclusion Criteria Arm intermediate risk (at least one of the criteria must be fulfilled): * pT3 and R0 and / or * histologically confirmed involvement of lymph nodes (n = 1-3) and no extracapsular extension of the lymph node metastasis Additional Inclusion Criteria Arm high risk (at least one of the criteria must be fulfilled): * residual tumor (R1 status) and / or * pathologic stage T4 (pT4) status and / or * more than 3 infected lymph nodes and / or * extracapsular extension of at least one lymph node metastasis Exclusion Criteria: * Patients with a cumulative nicotine abuse \> 30 packyears. These patients are not included in the intervention arms, but are always included in the observation arms (regardless of HPV status). * radiologically presumed or histologically confirmed distant metastasis * R2 resection or macroscopically visible residual tumor after surgery * no neck dissection * interval between last operation and planned irradiation start \> 7 weeks * contraindication against a guideline-appropriate adjuvant radiation or radiochemotherapy according to the clinical risk constellation * tumor disease in the last five years before the beginning of the study (except basaliomas of the skin, in-situ carcinoma of the cervix uteri or breast, or tumors with similar prognosis which are considered to be very likely to be cured) * malignant tumor disease in the head and neck region, regardless of interval and prognosis * Pre-irradiation with risk of dose overlap * participation in another clinical trial if further experimental therapy is necessary or the treatments/ protocols are mutually exclusive (e.g. altered chemotherapy, additional consolidation chemotherapy). Allowed is the additional participation in observation studies or supportive therapy studies. * diseases or conditions which do not allow the person concerned to assess the nature and scope and possible consequences of the clinical trial * pregnant or lactating women * evidence that the participant is not expected to comply with the study protocol (e.g. lack of cooperation) * missing written consent