%0 Journal Article
%T A dosimetric analysis of respiration-gated radiotherapy in patients with stage III lung cancer
%A Ren¨¦ WM Underberg
%A John R van S£¿rnsen de Koste
%A Frank J Lagerwaard
%A Andrew Vincent
%A Ben J Slotman
%A Suresh Senan
%J Radiation Oncology
%D 2006
%I BioMed Central
%R 10.1186/1748-717x-1-8
%X Gross tumor volumes (GTVs) were contoured in all 10 respiratory phases of a 4DCT scan in 15 patients with stage III NSCLC. Treatment planning was performed using different planning target volumes (PTVs), namely: (i) PTVroutine, derived from a single GTV plus 'conventional' margins; (ii) PTVall phases incorporating all 3D mobility captured by the 4DCT; (iii) PTVgating, incorporating residual 3D mobility in 3¨C4 phases at end-expiration. Mixed effect models were constructed in order to estimate the reductions in risk of lung toxicity for the different PTVs.Individual GTVs ranged from 41.5 ¨C 235.0 cm3. With patient-specific mobility data (PTVall phases), smaller PTVs were derived than when 'standard' conventional margins were used (p < 0.001). The average residual 3D tumor mobility within the gating window was 4.0 ¡À 3.5 mm, which was 5.5 mm less than non-gated tumor mobility (p < 0.001). The reductions in mean lung dose were 9.7% and 4.9%, respectively, for PTVall phases versus PTVroutine, and PTVgating versus PTVall phases. The corresponding reductions in V20 were 9.8% and 7.0%, respectively. Dosimetric gains were smaller for primary tumors of the upper lobe versus other locations (p = 0.02). Respiratory gating also reduced the risks of radiation-induced esophagitis.Respiration-gated radiotherapy can reduce the risk of pulmonary toxicity but the benefits are particularly evident for tumors of the middle and lower lobes.As lung tumors can show significant respiration-induced motion [1,2], sufficient margins have to be added to account for target mobility in radiotherapy planning [3]. For stage I non-small cell lung cancer (NSCLC), commonly used 'population-based' margins result in unnecessary irradiation of significant amounts of normal tissue [2,4], thereby increasing the risk of toxicity. For stage III NSCLC, local control after radiotherapy is poor [5,6], and both radiation dose-escalation and concurrent chemo-radiotherapy schemes have been used in an attempt to impr
%U http://www.ro-journal.com/content/1/1/8