The aim of the study was to investigate the potential clinical benefit from both target tailoring by excluding the tumour-free proximal part of the uterus during image-guided adaptive radiotherapy ... Show moreThe aim of the study was to investigate the potential clinical benefit from both target tailoring by excluding the tumour-free proximal part of the uterus during image-guided adaptive radiotherapy (IGART) and improved dose conformity based on intensity-modulated proton therapy (IMPT).The study included planning CTs from 11 previously treated patients with cervical cancer with a > 4-cm tumour-free part of the proximal uterus on diagnostic magnetic resonance imaging (MRI). IGART and robustly optimised IMPT plans were generated for both conventional target volumes and for MRI-based target tailoring (where the non-invaded proximal part of the uterus was excluded), yielding four treatment plans per patient. For each plan, the V-15Gy, V-30Gy, V-45Gy and D-mean for bladder, sigmoid, rectum and bowel bag were compared, and the normal tissue complication probability (NTCP) for >= grade 2 acute small bowel toxicity was calculated.Both IMPT and MRI-based target tailoring resulted in significant reductions in V-15Gy, V-30Gy, V-45Gy and D-mean for bladder and small bowel. IMPT reduced the NTCP for small bowel toxicity from 25% to 18%; this was further reduced to 9% when combined with MRI-based target tailoring. In four of the 11 patients (36%), NTCP reductions of > 10% were estimated by IMPT, and in six of the 11 patients (55%) when combined with MRI-based target tailoring. This > 10% NTCP reduction was expected if the V-45Gy for bowel bag was > 275 cm(3) and > 200 cm(3), respectively, during standard IGART alone.In patients with cervical cancer, both proton therapy and MRI-based target tailoring lead to a significant reduction in the dose to surrounding organs at risk and small bowel toxicity. Show less
