Brachytherapy

History

The first documented effort of brachytherapy goes back to the start of the 1900’s when Pasteau and Degrais inserted radium 226 capsules into the prostate through the urethra using digital rectal guidance. Brachytherapy in America began in 1917, when Barringer inserted radium 226 into the prostate using needles. During the 1950’s and 1960’s, Flocks used a solution of colloidal radioactive gold 198 to treat patients with prostate cancer who could not undergo surgery. Brachytherapy gained momentum in 1970’s with the development of radioactive iodine 125 and an open retropubic approach to implantation.

In the 1980’s, Holm’s implant technique in Denmark using a transperineal approach and transrectal ultrasonography was brought to America by Ragde. It is Holm’s implant technique that gave rise to modern day transrectal ultrasound-guided transperineal brachytherapy. The success of transrectal ultrasound-guided transperineal brachytherapy was its ability to implant radioactive sources with the desired precision.

In the 1990’s, Dr. Koutrouvelis developed the 3-D CT-guided posterior pararectal approach to overcome the limitations of the transrectal ultrasound-guided transperineal approach. Specifically, Dr. Koutrouvelis’ technique’s advancements include the ability to treat large glands without obstruction of the insertion of needles by the pubic arch, and use of a 3-D stereotactic system for precise placement and verification of correct positions of the needles in the target by computed tomography. Results of Dr. Koutrouvelis’ technique have been published. To read more on 3-D CT-Guided Pararectal Brachytherapy click here and for a listing of publications click here.

Radioactive Sources

The radioactive sources that have been used are iodine 125 (125I) since 1970, gold 198 (198Au) since 1972, iridium 192 (192Ir) since 1997, and palladium 103 (103Pd) since 1998.

The absorbed radiation of these sources in the prostate gland kills the cancerous cells while protecting the adjacent urinary bladder and rectum. The low dose rate and high attenuation of 125I and 103Pd sources allows us to treat large glands with permanent implant. In addition, for temporary implants, 192Ir is usually combined with EBRT.

Quality of Seeds

The quality of the seed implant
is the most important determinant of success of brachytherapy.
is evaluated only by post implant CT imaging.
is dependent on exactness of insertion and uniformity of distribution of seeds.
A good quality seed implant
has a maximum deviation of less than 10% from the prescribed radiation dose.
has good coverage of the treated target and has no seeds in the urethral wall, urinary bladder, or rectum.
Effectiveness of Seed Implant Quality:
Significant correlation found over time between quality of implant and morbidity.
Significant correlation found over time between quality of implant and long term clinical and biochemical success rate.

Methods of Brachytherapy

The implantation of radioactive sources is usually performed with transrectal ultrasound-guided transperineal approach with the patient in lithotomy position with general, epidural, or spinal anesthesia. Low risk patients are considered “ideal patients” for surgery, EBRT, and brachytherapy. However, according the treatment guidelines of the American Brachytherapy Society (ABS), brachytherapy with monotherapy is not recommended in patients with large volume prostate glands (> 60 cm3), pubic arch interference, medial lobe hypertrophy protruding in the urinary bladder, prostate calculi, post-transurethral prostate resection (TURP), obesity, or penile prosthesis. Transrectal ultrasound-guided transperineal brachytherapy is not possible in patients without rectum.

For high risk patients, a combination of brachytherapy and EBRT is performed with or without short or long-term hormone manipulation with transrectal ultrasound-guided transperineal brachytherapy. The radiation dosage in combined method with EBRT is 45 Gy and delivered to the entire pelvis and prostate. This dosage is insufficient to eradicate the cancerous cells outside the treatment target with brachytherapy as the cancerous cells are resistant to this amount of radiation. With our method of brachytherapy, 3-D CT-guided pararectal brachytherapy, we do not use combined method with EBRT as long as the prostate cancer is localized and there is no evidence of distant metastases.