Intensity-modulated radiotherapy vs. parotid-sparing 3D conformal radiotherapy
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cht · D. Nevens · S. Nuyts Department of Radiation Oncology, Leuvens Kankerinstituut, University Hospitals Leuven
Intensity-modulated radiotherapy vs. parotid-sparing 3D conformal radiotherapy Effect on outcome and toxicity in locally advanced head and neck cancer
Balancing tumor control against toxicity is a great challenge in the management of head and neck squamous cell carcinoma (HNSCC). The introduction of altered fractionation schedules and the addition of concurrent chemotherapy significantly improved locoregional control (LRC) and overall survival (OS) at the cost of increased acute and late toxicity [1, 2, 3]. Highly conformal radiation techniques allow the dose to the surrounding normal tissues to be reduced, while maintaining the dose to the target volume (TV). However, this high conformality also implies an increased risk for marginal misses and requires adequate compensation for setup uncertainties, appropriate selection and accurate delineation of the TV, proper dose prescription and extensive quality control. The field of HNSCC has always been at the forefront in the integration of these techniques, with the rapid and widespread implementation of parotid-sparing 3D conformal radiotherapy (3DCRT) and intensity-modulated radiotherapy (IMRT) [4, 5]. While IMRT has clear dosimetric advantages compared to the 3DCRT techniques, it does require considerably more effort from both a clinical and financial point of view. With this study we wanted to retrospectively investigate the effect of introducing IMRT compared to a selective 3DCRT approach in the primary treatment of locally advanced HNSCC on both outcome and toxicity.
Material and methods Patient selection This retrospective analysis was approved by the local medical ethical commission. A total of 245 patients with pathologically proven locally advanced HNSCC treated with primary (chemo-)radiotherapy were eligible for this analysis. Staging was performed according to the 2009 TNM classification system of the American Joint Committee on Cancer. Pretreatment evaluation consisted of complete history and physical examination, routine blood counts, liver function tests, ultrasound scan of the abdomen, chest radiography, esophagogastroscopy and tumor biopsy. All patients were imaged with computed tomography (CT) and/or magnetic resonance imaging (MRI) of the HNSCC region. Bone scans, positron emission tomography scans and CT scans of the abdomen or chest were obtained when clini cally indicated.
Simulation and TV delineation All patients were immobilized using a thermoplastic 5-point mask. A CT scan in treatment position of the HNSCC region was made for treatment planning (slice thickness 3 mm). The gross tumor volume (GTV) included any visible disease on imaging studies and/or physical examination. The clinical TV (CTV) encompassed a 10-mm margin with appropriate
anatomic correction around the GTV (= CTV boost) [6]. The elective nodal CTV was defined according to institutional guidelines, based on the validated proposals by Chao et al. [7] and Eisbruch e
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