High-dose-rate brachytherapy of rhabdomyosarcoma limited to the external auditory canal

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• 作者：Martin T. King¹ ; Laszlo Voros² ; Gil'ad N. Cohen² ; Ryan M. Lanning¹ ; Ian Ganly³ ; Chibuzo C. O'Suoji⁴ ; Suzanne L. Wolden¹ ; ^{woldens@mskcc.org}
• 关键词：Rhabdomyosarcoma ; High-dose rate ; External auditory canal ; Pediatrics
• 刊名：Brachytherapy
• 出版年：2017
• 出版时间：January-February 2017
• 年：2017
• 卷：16
• 期：1
• 页码：181-185
• 全文大小：827 K
• 卷排序：16

文摘

To report on the single-catheter high-dose-rate brachytherapy treatment of a 21-month-old girl child with an embryonal, botryoid-type, rhabdomyosarcoma limited to the external auditory canal (EAC).Methods and MaterialsA 2.4-mm diameter catheter was inserted into the right EAC and placed against the tympanic membrane. A computed tomography simulation scan was acquired. A brachytherapy treatment plan, in which 21 Gy in seven fractions was prescribed to a 1-mm depth along the distal 2 cm of the catheter, was generated. Treatments were delivered under anesthesia without complication. A dosimetric comparison between this plan and an intensity-modulated radiation therapy (IMRT) plan was then conducted. A clinical target volume (CTV), which encompassed a 1-mm margin along the distal 2 cm of the catheter, was delineated for both plans. Given positioning uncertainty under image guidance, a planning target volume (PTV = CTV + 3-mm margin) was defined for the IMRT plan. The IMRT plan was optimized for maximal CTV coverage but subsequently normalized to the same CTV volume receiving 100% of the prescription dose (V100) of the brachytherapy plan.ResultsThe IMRT plan was normalized to the brachytherapy CTV V100 of 82.0%. The PTV V100 of this plan was 34.1%. The PTV exhibited dosimetric undercoverage within the middle ear and toward the external ear. Mean cochlea doses for the IMRT and brachytherapy plans were 26.7% and 10.5% of prescription, respectively.ConclusionsFor rhabdomyosarcomas limited to the EAC, a standard brachytherapy catheter can deliver a highly conformal radiation plan that can spare the nearby cochlea from excess radiation.