Response Evaluation in Head and Neck Oncology: Definition and Prediction.

Curative treatment of head and neck squamous cell carcinoma includes surgery and/or (chemo)radiation, whereas in the palliative setting, chemotherapy and/or immunotherapy represent(s) the standard approach. With regard to quality control, methods for determining treatment response are sorely needed. For surgical therapy, histopathology is the standard quality control. Established criteria for high-risk patients include resection margins of the primary tumor and extracapsular extension of lymph node metastases. After definitive chemoradiation, treatment response is generally evaluated by tomographic imaging combined with endoscopy including re-biopsy of the tumor region. Single-cycle induction chemotherapy may be used to determine the radiosensitivity of tumors, helping to define surgical and nonsurgical treatment options. Innovative approaches with implications for prognosis include the analysis of immune infiltrates, liquid biopsy, molecular characterization (proteomics, genomics), molecular and functional imaging (PET-CT, PET-MRI), as well as advanced imaging data analysis (radio[geno]mics/texture analysis). Human papilloma virus, as a prognostically relevant parameter, is currently being investigated for de-escalation strategies. With regard to the extended personalization of oncologic therapy, markers predicting treatment response are desirable and seem to be important, also from a socioeconomic perspective.