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Local control after stereotactic body radiotherapy of centrally located lung tumours

High local control and low toxicity rates are seen in patients treated with stereotactic body radiotherapy (SBRT) for peripheral lung tumours [1,2]. According to the Advisory Committee on Radiation Oncology Practice (ACROP) consensus guideline, a fractionation schedule of at least 3x15Gy to the planning target volume (PTV) and escalated dose to the gross tumour volume (GTV) should be delivered [3,4]. For central lung tumours, similar attempts have been investigated and high local control rates have been obtained [5]. However, for these tumour sites, the high control rates may come at the cost of high toxicity rates, including fatal toxicity [5–8]. Differing dose and fractionation schedules have been proposed to optimise the therapeutic ratio, but to date no consensus has been obtained even though schedules below five fractions have been abandoned [6,9,10]. In some trials, a homogeneous dose distribution to the PTV has been used [11]. Contrary to this, other trials as e.g. the Scandinavian HILUS trial was based on an inhomogeneous dose distribution. In the HILUS trial, the dose was prescribed to the 67% isodose line encompassing the planning target volume, resulting in a maximum dose in the target of about 150% of the prescribed dose [12]. In this retrospective study, we analyse local control, survival and lethal toxicity in central lung tumours treated with eight fractions delivered in a two-week schedule. During the study period, the dose prescription and OAR constraints varied and we analyse the impact of different tumour and normal tissue doses.