Session Item

Definition of the optimal result in radiotherapy is elimination of all cancer (stem) cells so no surviving cells are left that eventually can result in disease recurrence. Radiotherapy is a local treatment modality and a deliberate effort during treatment planning is made to encompass macroscopic (GTV) and microscopic (CTV) disease into the final treatment volume to maximise treatment results. In decades before advanced diagnostic imaging modalities and technical possibilities of treatment delivery and planning systems, the uncertainty of real disease expansion was substantial. Thus CTV volumes included often at least 1 cm around GTV and often the whole anatomical compartment. Advanced diagnostics and gained knowledge from analysing surgical specimens of removed tumours made it possible to optimise tumour identification and reduce the GTV to high dose CTV margin more objectively and less by speculations.

Despite high biological doses given to eradicate cancer, recurrences occur most often at the primary disease sites. Several attempts to identify the subvolumes of treatment volumes that could be boosted with a higher dose, or patients with positive predictors of disease that could maybe receive de-escalated treatment instead, sparing them from side effects have been attempted. However, recurrences in the GTV are still the most frequent and hence biological radio resistance is still the most important topic in treatment success.

I aim to review the changes in treatment margins from GTV to CTV using head and neck cancer patients and their treatment as examples. Besides, I would like to review the knowledge of loco-regional recurrences in head and neck cancer patients and make some highlights in potential ways to improve disease control.