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

Overview

abstract

  • PURPOSE: 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 MATERIALS: A 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. RESULTS: The 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. CONCLUSIONS: For 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.

publication date

  • August 12, 2016

Research

keywords

  • Brachytherapy
  • Ear Canal
  • Ear Neoplasms
  • Radiotherapy Planning, Computer-Assisted
  • Radiotherapy, Intensity-Modulated
  • Rhabdomyosarcoma, Embryonal

Identity

PubMed Central ID

  • PMC5253256

Scopus Document Identifier

  • 84995569490

Digital Object Identifier (DOI)

  • 10.1016/j.brachy.2016.07.003

PubMed ID

  • 27528589

Additional Document Info

volume

  • 16

issue

  • 1