A Comparative Study of Volumetric Intensity Modulated Arc Therapy Versus Conventional IMRT in Head and Neck Cancer Patients
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- Category: Vol. 82, June 2014
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A Comparative Study of Volumetric Intensity Modulated Arc Therapy Versus Conventional IMRT in Head and Neck Cancer Patients, MOHAMED A. DAOUD, MAHA A. ALIDRISI, AHMAD S. HABASH and SEHAM E. ABDELKHALEK
Abstract
Background: Intensity-modulated radiation therapy (IM-RT) is now the method of choice for the treatment of patients with complex-shaped planning target volumes (PTV) targets, especially when concave targets are close to a larger number of organs-at-risk (OAR) as in patients with advanced head and neck cancer.
Patients and Methods: Fifteen patients with advanced head and neck cancers (oropharynx, Nasopharynx, and larynx) were selected for this study. Quantitative evaluation of plans was performed by means of standard Dose-Volume Histogram (DVH). The mean dose, V<95 and V>107 was scored for each PTV. The Dose Homogeneity Index (DHI) describes the uniformity of the dose within the planning target volume and is a ratio of the minimum dose (D99.5%) to the maximum dose (D0.5%). Another measure for the dose homogeneity was the standard deviation (SD) of the PTV doses. For the OAR, the mean dose (D-mean) to the parotid glands was scored, the maximum dose to the spinal cord and brain stem, and the mean dose to the oral cavity and the laryngeal area.
Results: The dose homogeneity to PTV1, PTV2 and PTV3 were the same for both RA and IMRT. The number of MU per fraction of 2.2Gy resulted to be MU/frIMRT= 1875.73±402 and MU/frRA=588±122 (31% of MU for IMRT) which is statistically significant difference (p=0.00). For the parotid glands the dose was 2Gy lower with RA plans compared with IMRT.
Conclusion: RA is a fast, safe, and accurate technique that uses lower MUs than conventional IMRT. Double arc plans provided better sparing of OAR better than IMRT.