Ultrasound-Guided Treatment of Prostatic Cancer: Brachytherapy

Fig. 33.1

Brachytherapy for prostate cancer treatment (Picture taken from the Internet: http://www.prostatecancertreatment.co.uk/treatment-options/brachytherapy)

33.1.2 Eligibility Criteria for Transperineal Brachytherapy

Transperineal brachytherapy has been demonstrated a safe and effective technique in all patients affected by prostate cancer if they have the following characteristics [8]:

Stage cT1b-T2a
No pathologic evidence of pelvic lymph node involvement
No distant metastases
Gleason score <7
An initial PSA level of <10 ng/mL
<50 % of biopsy cores involved with cancer
A prostate volume of <50 cm³
An International Prostate Symptom Score (IPSS) <12

33.1.3 Procedure

The brachytherapy procedure involves two phases:

Treatment planning
Treatment section

The treatment planning phase can be performed prior to or at the time of brachytherapy using nomograms or treatment planning computers. Brachytherapy sources may be implanted temporarily or permanently:

1.

Permanent seed implants (low–dose–rate brachytherapy) (LDR) – Low-dose brachytherapy treatments can be delivered with iodine or palladium seeds.
2.

A high-dose-rate brachytherapy (HDR) (pick-up existing figure, sample HDR brachytherapy case) implant is a temporary seed containing iridium 192 (Ir-192).

33.1.3.1 Low-Dose-Rate Brachytherapy (LDR)

With the patient in gynaecological position, with urinary catheter and under general anaesthesia or spinal block, an ultrasound probe is inserted into the rectum and multiple measurements taken to assess the dimensions and configuration of the prostate and its relationship to other structures, such as the urethra (Fig. 33.2).

Fig. 33.2

Gynaecological patient’s position under anaesthesia (Picture taken from the Internet: http://tidsskriftet.no/article/21010/en_GB)

In brachytherapy, catheter reconstruction is one of the most important procedures in treatment planning and relates the source tracks and dwell positions to the patient’s anatomy (e.g. targets and organs at risk) [6]. All information obtained from the ultrasound study of the prostate are acquired and analysed by dedicated software in order to establish a treatment plan, individualised to produce an ideal ‘bespoke’ plan of therapy for that person. The analysis phase is performed by a urologist, dedicated radiotherapist and physicist.

The dosimetric planning of the implant is generally performed in all patients during seed insertion. The dose is quantified in terms of the unit of absorbed energy per weight of tissue. In brachytherapy, the sharp radiation dose falloff allows a high degree of rectal sparing and permits delivery of a higher total dose to the prostate gland itself (Fig. 33.3). The average dose rates are 10 Gy/week for IMRT, 40 Gy/week for Pd-103 brachytherapy implants and 13 Gy/week for I-125 brachytherapy.

Fig. 33.3

Treatment planning and dose calculation (Picture taken from the Internet: http://www.cancertherapyadvisor.com/prostate-cancer/prostate-cancer-low-dose-brachytherapy-boost-survival-improvement/article/400686/)

The metal grid is set up and secured to the operating table. Through the grid, needles are inserted through the skin of the perineum into the prostate gland, under direct vision using the transrectal probe. When the positioning of the needles is satisfactory and matches the defined radiotherapy treatment plan, the seeds are deposited (Fig. 33.4). The time taken for this procedure ranges from 1 to 2 h.

Fig. 33.4

Seed implantation (Picture taken from the Internet: http://emedicine.medscape.com/article/453349-technique)

33.1.3.2 High-Dose-Rate Brachytherapy

High-dose-rate (HDR) brachytherapy can be used as the only treatment for prostate cancer, or it can be used in combination with external beam radiation therapy (EBRT). In the first case, it is known as ‘HDR monotherapy’, and when given with external beam, it is known as ‘combined HDR and EBRT’:

HDR monotherapy
- Used for localised prostate cancer disease (T1c-T2b; PSA <15; GS ≤3 + 4).
Combined high–dose–rate (HDR) brachytherapy and external beam radiation therapy (EBRT)
- Used for patients with locally more advanced disease within or around the prostate, those with higher PSA levels or higher pathology (Gleason 8–10) grade. EBRT is generally performed 2 weeks later.

High-dose-rate prostate brachytherapy, originally used as a boost together with external beam treatment, has been receiving more attention as monotherapy for suitable patients, due to its better-controlled dosimetry, no residual radioactivity, higher dose rate and better suitability for low α/β ratio prostate cancer [6]. Typically, in a template-guided prostate HDR implant, 15–18 catheters are inserted through the perineum into the prostate, under the guidance of transrectal ultrasound (TRUS) (Figs. 33.5 and 33.6).