ResultsAfter a mean follow-up of 50 months, 35 (15%) local failures were observed. MRI imaging was available for 27 (77%) of recurred patients. Only one recurrence was located completely outside the initial PTV. The mean proportions of the volume of recurrence inside the initial target structures were 47%(5-86%) for the GTV, 74%(27-100%) for the high-dose PTV and 82%(16-100%) for the low-dose PTV. On univariable analysis, the following parameters were found to be significantly associated with an increased risk of local recurrence: GTV (D95, p= 0.05), GTV (V< 66Gy, p= 0.01), GTV (volume, p= 0.02), PTV (max, p= 0.02), PTV (V< 66Gy, p= 0.03), PTV (V< 59Gy, p= 0.02), PTV (volume, p= 0.01). From multivariable analysis, GTV (volume, p< 0.05) and PTV (V< 59Gy, p< 0.05) were found to be indicators for significantly reduced local control with GTV (volume)> 26.5 cc differentiating between 78% and 85% rates …