From the Guidelines
The most effective scheme for simultaneous boost radiotherapy in prostate cancer treatment is intensity-modulated radiation therapy (IMRT) with simultaneous integrated boost (SIB), delivering 76-78 Gy to the prostate in combination with long-term androgen deprivation therapy (ADT) as recommended by the European Urology guidelines 1.
Schemes for Simultaneous Boost Radiotherapy
Several schemes exist for simultaneous boost radiotherapy in prostate cancer treatment, including:
- Intensity-modulated radiation therapy (IMRT) with simultaneous integrated boost (SIB)
- Moderate hypofractionation schemes
- More aggressive hypofractionation
- Stereotactic body radiotherapy (SBRT)
Recommended Treatment
The European Urology guidelines recommend offering patients IMRT/VMAT plus IGRT with 76-78 Gy in combination with long-term ADT (2-3 years) 1.
Focal Boosting
Focal boosting to MRI-defined dominant intraprostatic tumour can be offered when using normofractionated IMRT/IGRT (1.8-2.0 Gy per fraction) ensuring that organ at risk constraints are not exceeded 1.
Brachytherapy Boost
Brachytherapy boost (either HDR or LDR) can be offered to patients with good urinary function in combination with long-term ADT (2-3 years) 1.
Treatment Delivery
Treatment is typically delivered daily, five days per week, and patients should maintain a consistent bladder and rectal preparation protocol throughout treatment.
Biological Rationale
The biological rationale is that prostate cancer has a low alpha/beta ratio, making it more sensitive to higher doses per fraction compared to surrounding normal tissues, which allows for better tumor control with acceptable side effects.
From the FDA Drug Label
When ZOLADEX is given in combination with radiotherapy and flutamide for patients with Stage T2b-T4 (Stage B2-C) prostatic carcinoma, treatment should be started 8 weeks prior to initiating radiotherapy and should continue during radiation therapy. A treatment regimen using a ZOLADEX 3.6 mg depot 8 weeks before radiotherapy, followed in 28 days by the ZOLADEX 10. 8 mg depot, can be administered. Alternatively, four injections of 3.6 mg depot can be administered at 28-day intervals, two depots preceding and two during radiotherapy.
The schemes with simultaneous boost of radiotherapy in prostate cancer involve:
- Starting treatment with ZOLADEX 8 weeks prior to initiating radiotherapy and continuing during radiation therapy 2
- Using a treatment regimen with ZOLADEX 3.6 mg depot 8 weeks before radiotherapy, followed by ZOLADEX 10.8 mg depot 28 days later
- Administering four injections of 3.6 mg depot at 28-day intervals, with two depots preceding and two during radiotherapy 2 Key points:
- ZOLADEX is used in combination with radiotherapy and flutamide for Stage T2b-T4 prostatic carcinoma
- Treatment should start 8 weeks before radiotherapy and continue during radiation therapy
- Different dosing regimens are available, including 3.6 mg and 10.8 mg depots 2