Surface applicators for high dose rate brachytherapy in AIDS-related Kaposi's sarcoma.
OBJECTIVE
The development of commercially available surface applicators using high dose rate remote afterloading devices has enabled radiotherapy centers to treat selected superficial lesions using a remote afterloading brachytherapy unit. The dosimetric parameters of these applicators, the clinical implementation of this technique, and a review of the initial patient treatment regimes are presented.


METHODS
A set of six fixed-diameter (1, 2, and 3 cm), tungsten/steel surface applicators is available for use with a single stepping-source (Ir-192, 370 GBq) high dose rate afterloader. The source can be positioned either in a parallel or perpendicular orientation to the treatment plane at the center of a conical aperture that sits at an SSD of approximately 15 mm and is used with a 1-mm thick removable plastic cap. The surface dose rates, percent depth dose, and off-axis ratios were measured. A custom-built, ceiling-mounted immobilization device secures the applicator on the surface of the patient's lesion during treatment.


RESULTS
Between November 1994, and September 1996, 16 AIDS-related Kaposi's sarcoma patients having a total of 120 lesions have been treated with palliative intent. Treatment sites were distributed between the head and neck, extremity, and torso. Doses ranged from 8 to 20 Gy, with a median dose of 10 Gy delivered in a single fraction. Treatments were well tolerated with minimal skin reaction, except for patients with lesions treated to 20 Gy who developed moderate/severe desquamation.


CONCLUSIONS
Radiotherapy centers equipped with a high dose rate remote afterloading unit may treat small selected surface lesions with commercially available surface applicators. These surface applicators must be used with a protective cap to eliminate electron contamination. The optimal surface dose appears to be either 10 or 15 Gy depending upon the height of the lesion.
Evans
M D
MD
Department of Radiation Oncology, Royal Victoria Hospital, McGill University, Montréal, QC, Canada.
Yassa
M
M
Podgorsak
E B
EB
Roman
T N
TN
Schreiner
L J
LJ
Souhami
L
L
D000163:Acquired Immunodeficiency Syndrome / Q000150:complications*; D000328:Adult; D001918:Brachytherapy / Q000295:instrumentation* / Q000379:methods; D006801:Humans; D008297:Male; D008875:Middle Aged; D011879:Radiotherapy Dosage; D012514:Sarcoma, Kaposi / Q000209:etiology / Q000532:radiotherapy*; D012878:Skin Neoplasms / Q000209:etiology / Q000532:radiotherapy*