Can less radiation be safer without sacrificing cancer control?

Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.

Inclusion Criteria: 1. Histologic proven squamous cell carcinoma of the oral cavity/larynx/oro- or hypopharynx 2. Postoperative tumor status: * Oral cavity, oropharynx or larynx: pT1-3, pN0-pN2b * Hypopharynx: pT1-2; pN1 3. Patients that fulfill one or both of the following criteria: * ≤ pT2, R ≥ 5 mm, L0, Pn0 * ≤ 3 ipsilateral lymph node metastases (if a contralateral adequate neck dissection is performed, no contralateral neck dissection is recommended in patients with strictly ipsilateral localised tumors of the oropharynx or oral cavity) 4. R0-Resection (resection margin ≥ 1mm) 5. No distant metastasis cM0 6. age ≥ 18 years, no upper age limit 7. ECOG ≤ 2 8. Patients that understood protocol contents and are able to behave according to protocol 9. Signed study-specific consent form prior to therapy 10. In case of indicated simultaneous chemotherapy: * adequate bone marrow function (leucocytes \> 3,5x10\^3, platelets \> 100x 10\^3, hemoglobin \> 10g/dl * sufficient liver function: bilirubin \< 2,0mg/dl, ALT, AST \< less than 3 times upper limit of normal * sufficient renal function: normal serum creatinine, glomerular filtration rate \> 60ml/min Exclusion Criteria: 1. pregnant or lactating/nursing women 2. fertile patients that are not willing to use highly effective methods of contraception (per institutional standards) during treatment 3. Any condition potentially hampering compliance with the study protocol and follow-up schedule 4. On-treatment participation on other trials 5. R1 or R2 resection status 6. pN2c and pN3 7. cM1 8. prior radiotherapy in the head and neck region , prior chemo- or immunotherapy (neoadjuvant/induction) 9. time between surgery and beginning of radio(chemo)therapy \> 6 weeks 10. Prior (\> 4 months before beginning of radio(chemo)therapy) neck dissection 11. In case of indicated simultaneous chemotherapy: * reduced hearing ability (especially upper frequency range) * known dihydropyrimidindehydrogenase (DPD) deficiency * simultaneous therapy with brivudin or other DPD-inhibitors * uncontrolled serious disease, including physical and mental diseases, for example within last 6 months:instable angina pectoris, heart attack, serious cardiac dysrhythmias, stroke, serious carotid stenosis, neurologic or psychiatric disorders including epilepsy, dementia, psychosis; uncontrolled infection; liver cirrhosis Child B or C, severe hepatic impairment; severe blood count changes; severe renal impairment, HIV