Adaptive radiation therapy in head and neck cancer for clinical practice: state of the art and practical challenges

Abstract

Modern radiation therapy techniques are characterized by high conformality to tumor volumes and steep dose gradients to spare normal organs. These techniques require accurate clinical target volume definitions and rigorous assessment of set up uncertainties using image guidance, a concept called image-guided radiation therapy. Due to alteration of patient anatomy, changes in tissue density/volumes and tumor shrinkage over the course of treatment, treatment accuracy may be challenged. This may result in excessive irradiation of organs at risk/healthy tissues and undercoverage of target volumes with a significant risk of locoregional failure. Adaptive radiation therapy (ART) is a concept allowing the clinician to reconsider the planned dose based on potential changes to accurately delivering the remaining radiation dose to the tumor while optimally minimizing irradiation of healthy tissues. There is little consensus on how to apply this concept in clinical practice. The current review investigates the current ART issues, including patient selection, clinical/dosimetric criteria and timing for re-planning, and practical technical issues. A practical algorithm is proposed for patient management in cases where ART is required.

Analysis of geometric variation of neck node levels during image-guided radiotherapy for nasopharyngeal carcinoma: recommended planning margins

“…Several studies (3,4,25) quantified the volume and/or positional changes of the primary tumor and metastatic neck LNs in patients with head and neck squamous cell cancer and suggested that the volume of tumors and targets decreased and their positions were displaced considerably. For head and neck cancer, the volume reduction of middle-low risk clinical target volumes including most NNLs was 7.1-10.7% and the radiation dose increased substantially (26). However, the volume changes of level I A did not show the time-trend as the others did, which this discrepancy might be partially attributed to the variable positions of the jaw in each repeat CT scanning.…”

“…Replanning during treatment might be one feasible method (2). However, the optimal timing and the definition of volumes had little consensus (26). In previous studies, adaptive correction was suggested in the early stage of treatment, as it might be potentially feasible (4,18).…”

Principles of Radiation Therapy in Older Adults

“…Finally, with daily imaging, the volume of tissue irradiated can be decreased as the patient responds to therapy. This new strategy is called adaptive radiation and allows real time tracking of tumor response during the weekly therapy so that adjustments can be made that will increase the volume of normal tissue preserved from the high-dose regions (Veresezan et al 2017).…”

Head and neck cancer: improving outcomes with a multidisciplinary approach

“…However, no definitive recommendation can be made since the median follow-up was relatively short and the studies on TORS enrolled, on average, earlier-stage OPCs compared to IMRT studies. 43 , 44 …”