De-Escalation Strategies of (Chemo)Radiation for Head-and-Neck Squamous Cell Cancers-HPV and Beyond.

Oncological outcomes for head-and-neck squamous cell carcinoma (HNSCC) patients are still unsatisfactory, especially for advanced tumor stages. Besides the moderate survival rates, the prevalence of severe treatment-induced normal tissue toxicities is high after multimodal cancer treatments, both causing significant morbidity and decreasing quality of life of surviving patients. Therefore, risk-adapted and individualized treatment approaches are urgently needed for HNSCC patients to optimize the therapeutic gain. It has been a well-known fact that especially HPV-positive oropharyngeal squamous cell carcinoma (OSCC) patients exhibit an excellent prognosis and may therefore be subject to overtreatment, resulting in long-term treatment-related toxicities. Regarding the superior prognosis of HPV-positive OSCC patients, treatment de-escalation strategies are currently investigated in several clinical trials, and HPV-positive OSCC may potentially serve as a model for treatment de-escalation also for other types of HNSCC. We performed a literature search for both published and ongoing clinical trials and critically discussed the presented concepts and results. Radiotherapy dose or volume reduction, omission or modification of concomitant chemotherapy, and usage of induction chemotherapy are common treatment de-escalation strategies that are pursued in clinical trials for biologically selected subgroups of HNSCC patients. While promising data have been reported from various Phase II trials, evidence from Phase III de-escalation trials is either lacking or has failed to demonstrate comparable outcomes for de-escalated treatments. Therefore, further data and a refinement of biological HNSCC stratification are required before deescalated radiation treatments can be recommended outside of clinical trials.