What are the American Society of Clinical Oncology (ASCO) guidelines for brachytherapy in prostate cancer treatment?

ASCO Guidelines on Brachytherapy for Prostate Cancer

The 2017 ASCO/Cancer Care Ontario joint guideline provides risk-stratified recommendations for brachytherapy in prostate cancer, with brachytherapy boost strongly recommended for intermediate and high-risk disease when combined with external beam radiation therapy (EBRT), while low-dose rate (LDR) brachytherapy monotherapy remains an acceptable option for low-risk and select low-intermediate risk patients. 1

Risk-Stratified Treatment Recommendations

Low-Risk Prostate Cancer

• For patients requiring or choosing active treatment, LDR brachytherapy alone, EBRT alone, or radical prostatectomy should be offered as equivalent options. 1
• This recommendation remains unchanged from the original 2013 guideline as no new randomized data emerged to alter this approach. 1
• Five-year biochemical control rates exceed 85% with LDR brachytherapy monotherapy in this population. 2

Intermediate-Risk Prostate Cancer

• Patients with intermediate-risk disease choosing EBRT (with or without androgen-deprivation therapy) should be offered brachytherapy boost using either LDR or high-dose rate (HDR) techniques. 1
• For low-intermediate risk disease specifically (Gleason 7 with PSA <10 ng/mL OR Gleason 6 with PSA 10-20 ng/mL), LDR brachytherapy alone may be offered as monotherapy. 1, 3
• Biochemical control rates range from 69-97% at 5 years for intermediate-risk patients treated with brachytherapy-based approaches. 2
• The addition of brachytherapy boost to EBRT provides superior disease control compared to EBRT alone in this risk group. 1

High-Risk Prostate Cancer

• Patients with high-risk disease receiving EBRT and androgen-deprivation therapy should be offered brachytherapy boost (LDR or HDR). 1
• Brachytherapy monotherapy is NOT appropriate for high-risk disease; combination therapy with EBRT and ADT is mandatory. 4
• Five-year biochemical control rates range from 63-80% with combination brachytherapy boost approaches. 2
• High-risk patients require at least 24 months of ADT in combination with radiation therapy. 4

Isotope Selection for LDR Brachytherapy

Both Iodine-125 (¹²⁵I) and Palladium-103 (¹⁰³Pd) are reasonable isotope options for LDR brachytherapy. 1

• No recommendation can be made for or against using Cesium-131 (¹³¹Cs) due to insufficient evidence. 1
• Median time to urinary symptom resolution is approximately 1 year for Iodine-125 versus 6 months for Palladium-103. 5

HDR Brachytherapy Considerations

No recommendation can be made for or against HDR brachytherapy as monotherapy due to insufficient randomized evidence. 1

• HDR brachytherapy is endorsed as a boost technique when combined with EBRT for intermediate and high-risk disease. 1
• HDR offers advantages including lower operator dependence and typically fewer acute irritative symptoms compared to LDR. 2

Patient Eligibility and Contraindications

Patients Ineligible for Brachytherapy Include:

• Those with moderate to severe baseline urinary symptoms 1
• Large prostate volume (though neoadjuvant ADT may cytoreduce the prostate sufficiently to allow brachytherapy) 1
• Prior transurethral resection of the prostate 1
• Medical unfitness for the procedure 1
• Contraindications to radiation treatment 1

Important Caveats:

• Brachytherapy can exacerbate urinary obstructive symptoms and should be used cautiously in patients with significant lower urinary tract symptoms. 3
• There may be increased genitourinary toxicity compared with EBRT alone. 1
• Combination therapy (brachytherapy boost with EBRT) is associated with worse urinary, bowel, and sexual symptoms than monotherapy. 5

Quality Assurance Requirements

Brachytherapy should be performed only at centers following strict quality-assurance standards. 1, 4

• Centers must have appropriate technology, physics expertise, and clinical experience. 4
• Image-guided delivery systems are required for precise targeting. 4
• Grade 3-4 toxicities are rare (<4% in most series) when quality standards are maintained. 2

Androgen-Deprivation Therapy Integration

• ADT may be given in neoadjuvant, concurrent, and/or adjuvant settings at physician discretion. 1
• For unfavorable intermediate-risk disease, 4-6 months of ADT is recommended when combined with radiation. 3
• Patients should be informed that ADT with radiation increases adverse effects on sexual function. 3

Counseling and Shared Decision-Making

Patients should be counseled about all management options (surgery, EBRT, active surveillance as applicable) in a balanced, objective manner, preferably from multiple disciplines. 1

• The guideline emphasizes that survival advantages for brachytherapy compared with EBRT alone cannot be definitively determined, as trials were not designed or powered to detect meaningful differences in survival outcomes. 1
• Ten-year overall survival exceeds 85%, with cancer-specific mortality below 5% across brachytherapy-treated populations. 2
• Quality of life is improved in patients receiving brachytherapy compared to those undergoing surgery. 2

Clinical Trial Participation

Patients should be encouraged to participate in clinical trials testing novel or targeted approaches. 1