Changes in the clinical target volume - simultaneous integrated boost (CTV-SIB) for each patient during the course of chemo-radiotherapy (CRT). The volume of the CTV-SIB is plotted as a percentage of the CTV-SIB from the start of CRT. Percentages are plotted against time in weeks. Week 0 corresponds to measurements taken on the planning-CT before the start of CRT. Week 1–6 are measurements from the weekly MV-CTs.