title: A pilot study of ultrasound-guided electronic brachytherapy for skin cancer.
abstract: OBJECTIVE
  Electronic brachytherapy (eBT) has gained acceptance over the past 5 years for the treatment of non-melanomatous skin cancer (NMSC). Although the prescription depth and radial margins can be chosen using clinical judgment based on visual and biopsy-derived information, we sought a more objective modality of measurement for eBT planning by using ultrasound (US) to measure superficial (< 5 mm depth) lesions.
  
  
  METHODS
  From December 2013 to April 2015, 19 patients with 23 pathologically proven NMSCs underwent a clinical examination and US evaluation of the lesions prior to initiating a course of eBT. Twenty lesions were basal cell carcinoma and 3 lesions were squamous cell carcinoma. The most common location was the nose (10 lesions). A 14 or 18 MHz US unit was used by an experienced radiologist to determine depth and lateral extension of lesions. The US-measured depth was then used to define prescription depth for eBT planning without an added margin. A margin of 7 mm was added radially to the US lateral extent measurements, and an appropriate cone applicator size was chosen to cover the target volume.
  
  
  RESULTS
  The mean depth of the lesions was 2.1 mm with a range of 1-3.4 mm, and the mean largest diameter of the lesions was 8 mm with a range of 2.6-20 mm. Dose ranged from 32-50 Gy in 8-20 fractions with a median dose of 40 Gy in 10 fractions. All patients had a complete response and no failures have occurred with a median follow-up of 12 months (range of 6-22 months). Also, no prolonged skin toxicities have occurred.
  
  
  CONCLUSIONS
  A routinely available radiological US unit can objectively determine depth and lateral extension of NMSC lesions for more accurate eBT treatment planning, and should be considered in future eBT treatment guidelines.
authors.affiliation: Department of Radiation Oncology.
authors.forename: Uma
authors.initials: U
authors.lastname: Goyal
authors.affiliation: Department of Radiation Oncology.
authors.forename: Yongbok
authors.initials: Y
authors.lastname: Kim
authors.affiliation: Department of Radiology, University of Arizona, Tucson, Arizona, USA.
authors.forename: Hina Arif
authors.initials: HA
authors.lastname: Tiwari
authors.affiliation: Department of Radiology, University of Arizona, Tucson, Arizona, USA.
authors.forename: Russell
authors.initials: R
authors.lastname: Witte
authors.affiliation: Department of Radiation Oncology.
authors.forename: Baldassarre
authors.initials: B
authors.lastname: Stea
keywords: electronic brachytherapy; skin cancer; ultrasound