|Year : 2015 | Volume
| Issue : 3 | Page : 669
Technical considerations in brachytherapy boost for a case of squamous cell carcinoma of the external auditory canal based on our case
Bhargavi Ilangovan1, Janos Stumpf1, V Murali2, Neetu Sasikumar1, Rathna Devi1
1 Department of Radiation Oncology, Apollo Speciality Hospitals, Chennai, Tamil Nadu, India
2 Department of Medical Physics, Apollo Speciality Hospitals, Chennai, Tamil Nadu, India
|Date of Web Publication||9-Oct-2015|
Department of Radiation Oncology, Apollo Speciality Hospitals, 320, Padma Complex, Cenotaph Road, Chennai - 600 035, Tamil Nadu
Source of Support: None, Conflict of Interest: None
Squamous cell carcinoma of the external auditory canal is a rare entity. The patients present with ear discharge and otalgia. They are treated with radiotherapy and surgery. Surgery with oncological priorities is quite complex with substantial consequences. We are reporting a patient with squamous cell carcinoma of the external auditory canal, who was treated with limited surgery followed by radiotherapy. Radiotherapy was a combination of external beam radiotherapy and brachytherapy. High dose rate brachytherapy was given using an ear speculum fixed with wax and a suction catheter. This article is to highlight the technique and dosimetry of the brachytherapy procedure.
Keywords: Brachytherapy, external auditory canal, radiotherapy
|How to cite this article:|
Ilangovan B, Stumpf J, Murali V, Sasikumar N, Devi R. Technical considerations in brachytherapy boost for a case of squamous cell carcinoma of the external auditory canal based on our case. J Can Res Ther 2015;11:669
|How to cite this URL:|
Ilangovan B, Stumpf J, Murali V, Sasikumar N, Devi R. Technical considerations in brachytherapy boost for a case of squamous cell carcinoma of the external auditory canal based on our case. J Can Res Ther [serial online] 2015 [cited 2020 May 26];11:669. Available from: http://www.cancerjournal.net/text.asp?2015/11/3/669/146108
| > Introduction|| |
Squamous cell carcinoma of the external auditory canal is quite rare and is treated with radiotherapy and surgery. Radiotherapy has been by external beam radiotherapy and/or Brachytherapy. The combination of external beam radiotherapy and Brachytherapy has been beneficial for tumors in this location. We treated one such patient with such a combination. Brachytherapy was done using an ear speculum fixed with wax and a suction catheter. This ensured adequate immobilization and efficient treatment delivery which is being discussed in detail.
| > Case report|| |
A 33-year-old gentleman was evaluated for complaints of ear discharge for a period of 6 months. Examination revealed granulation tissue in the external auditory canal. A computed tomography (CT) scan done revealed a mass in the medial part of the external auditory canal. He underwent surgery elsewhere. Biopsy revealed a well-differentiated squamous cell carcinoma. Follow-up magnetic resonance imaging in about 1 month after surgery showed multiple cysts in the canal with no residual lesion. He came to our hospital for further management. He underwent examination under general anesthesia and was found to have granulation tissue in the tympanic membrane and the anteroinferior part of the adjoining external auditory canal. The biopsy of the lesion revealed squamous cell carcinoma. He was referred for radiotherapy as he was reluctant to undergo the completion surgery. He underwent external beam radiotherapy (EBRT) up to a dose of 50 Gy in 25 fractions by three-dimensional conformal radiotherapy technique. Due to the position of the tumor, even a relatively simple field combination resulted in a highly acceptable dose distribution [Figure 1]. It was decided to irradiate further with a single fraction of brachytherapy, with an aim to deliver a dose of 6 Gy to the surface. A 12 French suction catheter was used as a coaxial applicator. It was passed inside a polypropylene ear speculum. Inside this, the treatment catheter was passed such that about 1 cm of the catheter protruded outside conical part of the speculum. The catheter and the speculum were fixed to each other and to the concha using moldable wax and tape [Figure 2].
The outer diameter of the suction catheter was 4 mm, inner diameter 2.45 mm. The outer diameter of the transfer catheter was 2.3 mm. This means, even if the catheter lops on to any one side of the suction catheter, the maximum positional error could be ± 0.075 mm. This is a submillimeter and not quite significant from dosimetry point of view.
The entire set up was fixed, and the planning CT scan with 2 mm slice thickness was done with the same set up. A treatment plan with the source step size of 2.5 cm was made. Dose was prescribed to the mucosa. After necessary optimization, a plan to deliver a dose of 6 Gy in a single fraction to the relevant portion of the external auditory canal was generated. The source transfer catheter was connected to the treatment microselectron unit through a coupling mechanism, and the dose was delivered [Figure 3].
The applicator remained fixed throughout the planning CT scan, treatment planning procedures and dose delivery, all of which lasted for about 1 h.
A biological dose equivalent of about 60 Gy was thereby delivered with a combination of EBRT and brachytherapy.
Patient tolerated the treatment well.
| > Discussion|| |
Squamous cell carcinoma constitutes 82% of the tumors involving the auditory canal, middle ear, and mastoid.  They present with otorrhea and otalgia. Chronic suppurative otitis media and previous irradiation are thought of as etiological factors.  They have an aggressive nature and are found to spread along vascular and neural pathways.  The main cause of death is, usually, aggressive local recurrence.  Hence, it is prudent to provide aggressive local treatment for these patients.
Early tumors are treated with radical surgery.  Postoperative radiotherapy has been found to be beneficial in reducing the local recurrence in these tumors, more so for those with questionable margins, nodal disease or T2-3 diseases. 
In our case, the patient had an early disease but was reluctant to undergo a completion surgery. It was decided to treat him aggressively. The literature has suggested that doses of over 60 Gy are related to better local recurrence-free survival than lower doses.  Brachytherapy was involved due to its efficacy in dose delivery with a rapid fall off, sparing the adjacent bone. The nonuniform contour and the eloquent location of the tumor were challenges for the dose delivery with external beam therapy. This was overcome by the use of high dose rate brachytherapy. The use of the polypropylene speculum and moldable wax enabled proper immobilization of the catheter and hence dose delivery. Patient movement was not a concern in brachytherapy. We could optimize the dose distribution such that the medial portion of the external auditory canal near the eardrum, where the tumor was found could be irradiated efficiently. The use of brachytherapy in combination with EBRT has been said to provide less side effects and better cosmesis. 
| > Conclusion|| |
Squamous cell carcinomas of the external auditory canal are, usually, diagnosed late due to the nonspecific presentation. The combination of surgery and radiotherapy would be the optimal treatment. Brachytherapy could be thought of in combination with EBRT, wherever possible. The high-risk areas thereby receive high doses, and this leads to better tumor control.
| > References|| |
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[Figure 1], [Figure 2], [Figure 3]