Ahmed Merina, Hansen Vibeke N, Harrington Kevin J, Nutting Christopher M
Department of Radiotherapy, The Royal Marsden Hospital, Sutton, United Kingdom.
Med Dosim. 2009 Fall;34(3):217-24. doi: 10.1016/j.meddos.2008.08.008. Epub 2008 Oct 1.
Radiation therapy for squamous cell carcinoma of the oral cavity may be curative, but carries a risk of permanent damage to bone, salivary glands, and other soft tissues. We studied the potential of intensity modulated radiotherapy (IMRT) to improve target volume coverage, and normal tissue sparing for advanced oral cavity carcinoma (OCC). Six patients with advanced OCC requiring bilateral irradiation to the oral cavity and neck were studied. Standard 3D conformal radiotherapy (3DCRT) and inverse-planned IMRT dose distributions were compared by using dose-volume histograms. Doses to organs at risk, including spinal cord, parotid glands, and mandible, were assessed as surrogates of radiation toxicity. PTV1 mean dose was 60.8 +/- 0.8 Gy for 3DCRT and 59.8 +/- 0.1 Gy for IMRT (p = 0.04). PTV1 dose range was 24.7 +/- 6 Gy for 3DCRT and 15.3 +/- 4 Gy for IMRT (p = 0.001). PTV2 mean dose was 54.5 +/- 0.8 Gy for 3DCRT and for IMRT was 54.2 +/- 0.2 Gy (p = 0.34). PTV2 dose range was improved by IMRT (7.8 +/- 3.2 Gy vs. 30.7 +/- 12.8 Gy, p = 0.006). Homogeneity index (HI) values for PTV2 were closer to unity using IMRT (p = 0.0003). Mean parotid doses were 25.6 +/- 2.7 Gy for IMRT and 42.0 +/- 8.8 Gy with 3DCRT (p = 0.002). The parotid V30 in all IMRT plans was <45%. The mandible V50, V55, and V60 were significantly lower for the IMRT plans. Maximum spinal cord and brain stem doses were similar for the 2 techniques. IMRT provided superior target volume dose homogeneity and sparing of organs at risk. The magnitude of reductions in dose to the salivary glands and mandible are likely to translate into reduced incidence of xerostomia and osteoradionecrosis for patients with OCC.
口腔鳞状细胞癌的放射治疗可能具有治愈性，但存在对骨骼、唾液腺和其他软组织造成永久性损伤的风险。我们研究了调强放射治疗（IMRT）改善晚期口腔癌（OCC）靶区覆盖及保护正常组织的潜力。研究了6例需要对口腔和颈部进行双侧照射的晚期OCC患者。通过剂量体积直方图比较标准三维适形放疗（3DCRT）和逆向计划IMRT的剂量分布。评估包括脊髓、腮腺和下颌骨在内的危及器官的剂量，作为放射毒性的替代指标。3DCRT的PTV1平均剂量为60.8±0.8 Gy，IMRT为59.8±0.1 Gy（p = 0.04）。3DCRT的PTV1剂量范围为24.7±6 Gy，IMRT为15.3±4 Gy（p = 0.001）。3DCRT的PTV2平均剂量为54.5±0.8 Gy，IMRT为54.2±0.2 Gy（p = 0.34）。IMRT改善了PTV2剂量范围（7.8±3.2 Gy对30.7±12.8 Gy，p = 0.006）。使用IMRT时，PTV2的均匀性指数（HI）值更接近1（p = 0.0003）。IMRT的平均腮腺剂量为25.6±2.7 Gy，3DCRT为42.0±8.8 Gy（p = 0.002）。所有IMRT计划中的腮腺V30均<45%。IMRT计划的下颌骨V50、V55和V60显著更低。两种技术的最大脊髓和脑干剂量相似。IMRT提供了更好的靶区剂量均匀性并保护了危及器官。唾液腺和下颌骨剂量降低的幅度可能会降低OCC患者口干症和放射性骨坏死的发生率。
