Intensity-modulated radiotherapy improves target coverage, spinal cord sparing and allows dose escalation in patients with locally advanced cancer of the larynx Catharine H. Clark a, * , A. Margaret Bidmead a , Cephas D. Mubata a , Kevin J. Harrington b , Christopher M. Nutting b a Joint Department of Physics, The Royal Marsden NHS Trust, Fulham Road, London SW3 6JJ, UK b Department of Radiotherapy, The Royal Marsden NHS Trust, Fulham Road, London SW3 6JJ, UK Received 8 October 2002; received in revised form 25 September 2003; accepted 23 October 2003 Abstract Background and purpose: An investigation has been carried out into the potential of intensity-modulated radiotherapy (IMRT) to improve the coverage of the targets and the sparing of the spinal cord (SC) in radiotherapy treatment of the larynx and bilateral cervical lymph nodes, in patients with advanced larynx cancer. Patients and methods: Conventional radiotherapy (CRT) and IMRT plans were produced for six patients to treat the larynx (PTV1) and lymph nodes (PTV2) to 50 Gy (phase 1). A second plan was created to treat the PTV1 to 65 Gy and PTV2 to 50 Gy (phases 1 and 2). The potential to escalate the dose to both the larynx (to 67 Gy) and the nodes (to 56 Gy) was investigated for the IMRT plans. Results: The phase 1 treatment gave average minimum doses (dose received by 99% volume) of 38.1 (^ 8.2) and 48.5 (^ 0.2) Gy for PTV1, treated by CRT and IMRT, respectively, and 35.9 (^ 2.9) and 46.2 (^ 1.8) Gy for PTV2. For the two phase treatment the average minimum doses to PTV1 were 51.6 (^ 8.2) (CRT) and 62.1 (^ 0.7) Gy (IMRT) ðP ¼ 0:028Þ and for PTV2 were 36.2 (^ 2.9) (CRT) and 46.8 (^ 0.5) Gy (IMRT) ðP ¼ 0:0004Þ: The average maximum doses (dose received by 1% volume) to the SC were 42.5 (^ 1.9) (CRT) and 37.9 (^ 1.4) Gy (IMRT) ðP ¼ 0:01Þ: For the dose escalated IMRT plans the minimum dose to PTV1 was 64.6 (^ 0.5) and 50.8 (^ 1.8) Gy to PTV2. The average SC maximum was 41.5 (^ 1.6) Gy. Conclusions: IMRT offers improved target homogeneity and reduces irradiation of the SC. This sparing of normal tissue structures is sufficient that significant dose escalation of both the larynx and lymph nodes may be possible. q 2003 Elsevier Ireland Ltd. All rights reserved. Keywords: Larynx carcinoma; Intensity-modulated radiotherapy; Dose escalation 1. Introduction External beam radiotherapy for advanced cancer of the larynx represents a difficult challenge for treatment planning because the planning target volume (PTV), which includes the larynx and bilateral cervical lymph nodes, is wrapped around the spinal cord (SC). Typically in the UK, lateral-opposed photon portals are used to treat the PTV up to cord tolerance and then reduced photon fields are matched to high-energy electrons bilater- ally to treat the posterior cervical lymph nodes [7,24]. This produces a concave dose distribution surrounding the SC, but there are areas of potential under-dose in the photon–electron match line that may account for a proportion of patients who relapse in the cervical nodes. Additionally the dose inhomogeneity in the PTV is high due to changes in contour of the head and neck region. These problems cannot be resolved entirely, simply by the use of 3D planning approaches. Dose inhomogeneity can be reduced using customised tissue compensation, but this is rarely used in routine clinical practice because of the complications of design and manufacture. A radiation dose of 65–75 Gy is required to eradicate macroscopic tumour in the larynx and involved lymph nodes, and 50 Gy elective irradiation to the cervical lymph nodes [9]. These doses are in excess of SC tolerance 0167-8140/$ - see front matter q 2003 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.radonc.2003.10.012 Radiotherapy and Oncology 70 (2004) 189–198 www.elsevier.com/locate/radonline * Corresponding author.