d) Radiotherapy

Radiotherapy can be used for any stage of prostate cancer, including metastatic disease where it remains a valuable tool in local control of symptoms. The radiotherapy techniques are quite varied and are covered in detail on daughter pages.

General Guidelines

Low Risk Disease

This includes patients with organ confined disease (T1c, T2a), with low Gleason score (6 or less) and with low PSA (< 10). Options for this group of patients include:

  • External beam radiotherapy (70-78 Gy in 35-39 fractions) alone
    • Target volume is the prostate gland alone with a 10 mm expansion except posteriorly of 6 mm
    • Dose is controversial; dose escalation above 74 Gy has been shown to improve biochemical recurrence free but not overall survival and 70 Gy is still considered standard in some centres for low risk disease.
  • Low dose rate brachytherapy (145 Gy (125I) or 125 Gy (103Pd))
    • Target volume is the prostate gland alone
    • Unlike external beam treatment, the ideal distribution of seeds is determined prior to delivery whereas actual dosimetry occurs 1 month post insertion (to allow time for swelling to settle post-insertion).

Intermediate Risk Disease

This group has the highest number of options. It includes patients with Gleason 7 disease, T2b/T2c, and those with PSA between 10 and 20. There is a spectrum of risk within the intermediate category, and some would consider patients with both Gleason 7 disease and PSA of over 10 to be 'high risk'.
Options include:

  • External beam radiotherapy (74-78 Gy in 27-29 fractions)
    • It is important to consider neoadjuvant androgen deprivation which was shown in the Bolla study to improve overall survival from 40% to 60% at 10 years in high risk patient groups. There are few studies on 'intermediate' groups; on retrospective studies the benefit in favourable intermediate patients (eg. T2b Gleason 6 or T1c Gleason 3+4 =7) appears to be minimal whereas the benefit in Gleason 4+3=7 or T2c patients was significant. The duration of neoadjuvant treatment should be 6 months as demonstrated in TROG 96-02.
  • Low dose rate permanent interstitial brachytherapy/High dose rate interstitial brachytherapy
    • This is considered investigational at present for this patient population. These patients are at added risk of extracapsular extension which is not sufficiently covered by brachytherapy alone.
  • Combination external beam radiotherapy with brachytherapy boost
    • This is possible with either low dose or high dose rate brachytherapy
    • With low dose rate brachytherapy, a similar approach is used to primary treatment except the total dose is lower (125I = 110 Gy, 103Pd = 90 Gy; i.e. 35 Gy less dose)
    • High dose rate brachytherapy can be used as a boost treatment in these patients as well. The dose is 50 Gy external beam to the prostate with a 19.5 Gy in 3 fraction boost to the prostate using HDR. The evidence in this setting is less compelling than for patients with high risk disease

High Risk Disease

These patients have locally advanced tumours (T3a, T3b, T4), lymph node metastases (N1), Gleason Scores above 7, or PSA above 20. These factors all predict for local and distant treatment failure and necessitate the highest level of treatment.
All patients should receive 6 months of androgen deprivation (level 1 evidence from Bolla and RTOG trials).
The main treatment options are:

  • External beam radiotherapy alone (78+ Gy in 29+ fractions)
    • Some dose escalation studies show improved local control with doses up to 86 Gy but and overall survival advantage has not been shown and there is concern about late toxicities with limited follow up.
  • External beam radiotherapy (50 Gy) + HDR brachytherapy (19.5 Gy in 3 #)
    • LDR brachytherapy is insufficient to provide an adequate dose to this tumour and is not used

Radiotherapy Techniques