Electrons Versus Surface Brachytherapy for Non-melanoma Skin Cancer- A Matched Pair Analysis

Advances in Skin Brachytherapy: Cosmesis and Function Preservation

Skin brachytherapy represents an excellent alternative treatment for patients with non-melanoma skin cancers. It offers superior conformity of dose distribution with rapid dose fall off, reducing the risk of radiotherapy-related treatment toxicity. A smaller treatment volume in brachytherapy, when compared with external beam radiotherapy, is conducive for hypofractionation, which is an attractive option for decreasing outpatient visits to the cancer centre, especially for elderly and frail patients. Skin brachytherapy is an excellent option to preserve function and cosmesis, especially in skin cancers located in the head and neck region. Electronic brachytherapy, image-guided superficial brachytherapy and 3D printed moulds are all emerging advances in skin brachytherapy.

Customized 3D-printed molds for high dose-rate brachytherapy in facial skin cancer: First clinical experience

BACKGROUND AND OBJECTIVE

Radiotherapy of elderly, frail patients with facial skin cancer in proximity to critical organs is challenging. This is the first report on clinical experience with facial skin cancer treated by individualized 3D-printer-based mold high-dose-rate (HDR) brachytherapy (BT).

PATIENTS AND METHODS

Fifteen patients not eligible for radical surgery or definitive external beam radiotherapy (EBRT) were treated with 3D-printer-based mold HDR-BT. Patient selection and treatment were in accordance with multidisciplinary tumor board recommendations. Clinical response, toxicity and cosmesis were analyzed.

RESULTS

Median age was 77 years. Histology revealed squamous cell carcinoma in seven, basal cell carcinoma in five, melanoma in situ in one, Lentigo maligna in one, and melanoma in one patient, respectively. Median prescription dose was 39 Gy delivered in once-daily fractions of 3 Gy. After a median follow-up of 12.2 months, local recurrence was observed in one patient with melanoma in situ. Apart from one grade 4 cataract, no other > grade 2 late toxicity was documented.

CONCLUSIONS

HDR-BT with 3D-printer-based molds for facial skin cancer is a well-tolerated and safe treatment option for elderly, frail patients not eligible for radical surgery or definitive EBRT due to functional inoperability or tumor location.

A novel conformal superficial high-dose-rate brachytherapy device for the treatment of nonmelanoma skin cancer and keloids

PURPOSE

To develop a novel conformal superficial brachytherapy (CSBT) device as a treatment option for the patient-specific radiation therapy of conditions including superficial lesions, postsurgical positive margins, Dupuytren's contractures, keloid scars, and complex anatomic sites (eyelids, nose, ears, etc.).

METHODS AND MATERIALS

A preliminary CSBT device prototype was designed, built, and tested using readily available radioactive seeds. Iodine-125 (¹²⁵I) seeds were independently guided to the treatment surface to conform to the target. Treatment planning was performed via BrachyVision Planning System (BPS) and dose distributions measured with Gafchromic EBT3 film. Percent depth dose curves and profiles for Praseodymium-142 (¹⁴²Pr), and Strontium-90/Yttrium-90 (⁹⁰Sr-⁹⁰Y) were also investigated as potential sources. Results achieved with ⁹⁰Sr-⁹⁰Y and electron external beam radiation therapy were compared and Monte Carlo N-Particle eXtended 2.6 simulations of ¹⁴²Pr seeds were validated.

RESULTS

BPS was able to predict clinical dose distributions for a multiple seeds matrix. Calculated and measured doses for the ¹²⁵I seed matrix were 500 cGy and 473.5 cGy at 5 mm depth, and 171.0 cGy and 201.0 cGy at 10 mm depth, respectively. Results of ⁹⁰Sr-⁹⁰Y tests demonstrate a more conformal dose than electron EBRT (1.6 mm compared to 4.3 mm penumbra). Measured ¹⁴²Pr doses were 500 cGy at surface and 17.4 cGy at 5 mm depth.

CONCLUSIONS

The CSBT device provides a highly conformal dose to small surface areas. Commercially available BPS can be used for treatment planning, and Monte Carlo simulation can be used for plans using beta-emitting sources and complex anatomies. Various radionuclides may be used in this device to suit prescription depths and treatment areas.