High
dose rate (HDR) brachytherapy is a technique that has become
accepted in cancer treatment over the past 10
years. Basically, hollow plastic catheters are
inserted into the organ that is involved with cancer
surgically. Then a CAT scan is carried out to image that
organ, the cancer and the surrounding tissues. The
radiation oncologist then determines how much radiation is
delivered to the cancer but at the same time limits the
radiation dose to the surrounding normal healthy
tissues. 
A computer program generates a plan whereby the highest
concentration of radiation is delivered to the cancer and the
lowest dose possible to the healthy surrounding
tissues. The radiation oncologists reviews this
plan and makes adjustments in the dose taking into account the
exact known location of the cancer and lowering doses further
to adjacent organs with may receive too much radiation.
This program is then transferred to a HDR (high dose rate)
machine.
The HDR unit has a single radiation source of
Iridium-192 welded to a long wire of 1-meter length (over 3
feet) controlled by computer driven motor. The catheters
are then attached to the HDR unit via transfer tubes.
Generally most HDR systems can treat 18-25 catheters at one
time. In the event a patient has more than 25 catheters,
the treatment is divided into multiple treatments--eg. a
patient has 30 catheters--the first 25 catheters are treated
and then immediately afterwards, the last 5 are treated by 
connecting
the last 5 catheters to the HDR unit. The HDR
motor can be controlled to millimeter accuracy to treatment
any point inside the catheter and therefore any position
inside the organ / cancer.
Provided the catheters are placed evenly
throughout the organ during the time of surgery, HDR treatment
allows the most accurate delivery of radiation to an
organ. The typical sites for treatment include:
Prostate, vaginal canal, rectal, bile duct, certain lung
cancers, brain tumors. HDR treatment may not be
appropriate in your situation depending on the location of the
cancer, your health or the type of cancer--so always consult
your physician for suitability of this treatment.
PROSTATE HDR:
In prostate HDR brachytherapy,
18-25 catheters are inserted through the perineum (the area
behind the scrotum and in front of the anus) under
anesthesia. With ultrasound guidance, the catheters are
advanced into the correct position into the prostate.
A plastic template is used to "hold" and secure the
catheters in the perineum. These catheters will stay in
place for 36-48 hours while the patient remains in the
hospital. The patient will be bed-bound during this time
as it will be critical that the catheters are not dislodged
during the stay.
A CAT scan is then taken to define
the position of the catheters and a treatment plan is
developed. After the plan has been refined and approved
by the radiation oncologist, the patient receives his first
HDR treatment. The plastic catheters are connected to
the HDR via flexible plastic connection tubes. 
A computer program then drives the source into each
catheter, each position for a specific time. These times
are locations are manually checked before the start of the
treatment. One HDR treatment typically lasts 10-15
minutes.
The
patient will typically receive 3 or 4 HDR treatments with each
implant with each treatment at least 6 hours from the previous
one, ie. the 3-4 HDR treatments will occur over 48
hours. Once the final HDR treatment has been delivered,
the catheters are removed and the patient discharged home with
suitable (usually several hours later).
HDR treatments are usually given
as a treatment prior to external beam radiotherapy, ie.
patients will receive 5 weeks of external beam radiotherapy
following their HDR treatment. The external beam
radiotherapy is given in cases where the risk of the prostate
cancer is either intermediate or high.
To determine your
risk,
.
In select patients, where
the risk is very low, patients may have a second set of HDR
treatments 2-3 weeks later, ie. the patients under a second
HDR implant as described above. These select patients
will NOT require 5 weeks of external beam radiotherapy.
This type of approach is called prostate HDR monotherapy.
Suitability for HDR monotherapy is extremely limited and
requires a thorough discussion with your physician.
Advantages:
1. Radiation is
precisely delivered to the prostate cancer (important for
intermediate or high risk
cancers where precision is critical).
2. Radiation is
precisely minimized to normal healthy tissues
3. Short
hospitalization (2-3 days)
4. Rapid recovery
(urination & bowel irritation mild)
5. No radiation safety
concerns for the patient
Disadvantages:
1. Most patients will
require 5 weeks of external beam following HDR
2. Long term data over
5 years has not yet matured however some current published
data demonstrates superiority of HDR + external treatment over
external beam treatment alone.
to view the journal article.
3. Prostatectomy
following HDR treatment is usually not possible in the event
of recurrence.
to view journal articles about prostate HDR treatment.
