What is the recommended treatment approach for a patient with localized prostate cancer who is a candidate for brachytherapy (radiation therapy using radioactive seeds)?

Brachytherapy for Localized Prostate Cancer

Brachytherapy as monotherapy is indicated for low-risk prostate cancer (cT1c-T2a, Gleason grade 2-6, PSA <10 ng/mL), with cancer-control rates exceeding 90% at medium-term follow-up, comparable to radical prostatectomy. 1

Patient Selection Criteria

Ideal candidates for permanent seed brachytherapy:

• Low-risk disease characteristics: clinical stage T1c-T2a, Gleason score ≤6, PSA <10 ng/mL 1, 2
• Prostate volume suitable for implantation (very large or very small prostates are problematic) 1
• Absence of significant lower urinary tract symptoms (low International Prostate Symptom Score) 1
• No prior transurethral resection of prostate (TURP increases incontinence risk substantially) 1
• Life expectancy >10 years 2, 3

Patients who should NOT receive brachytherapy monotherapy:

• High-risk disease (unless combined with external beam radiation therapy and androgen deprivation therapy) 1
• Previous TURP (significantly increased incontinence risk from acute retention and bladder neck contractures) 1
• Severe baseline urinary obstructive symptoms 1
• Very large prostate glands (neoadjuvant ADT may be used to shrink prostate to acceptable size) 1

Treatment Approach by Risk Category

Low-risk disease:

• Brachytherapy monotherapy is appropriate using either iodine-125 (145 Gy prescribed dose) or palladium-103 (125 Gy prescribed dose) 1
• Single modality treatment achieves >85% 5-year freedom from biochemical failure 4

Favorable intermediate-risk disease:

• Brachytherapy alone OR in combination with external beam radiation therapy (40-50 Gy) are acceptable options 1, 3
• When combining modalities, boost doses are 110 Gy for iodine-125 and 100 Gy for palladium-103 after 40-50 Gy external beam 1
• 5-year freedom from biochemical failure ranges 69-97% 4

High-risk disease:

• Brachytherapy should NOT be used as monotherapy 1
• If brachytherapy is used, it MUST be combined with external beam radiation therapy (40-50 Gy) PLUS 24-36 months of androgen deprivation therapy 1, 3
• This triple combination (brachytherapy + EBRT + ADT) reduces prostate cancer-specific mortality (adjusted HR 0.32; 95% CI 0.14-0.73) compared to brachytherapy alone 1

Technical Requirements

Mandatory technical standards:

• Dosimetric planning must be performed either prior to or during implantation 1
• Transrectal ultrasound guidance should be used for predictive dosimetry and seed placement 1
• Modified peripheral implantation technique is required to minimize urethral overdose (>200% of prescribed dose) 1
• Postimplantation dosimetry MUST be performed at 4 weeks for iodine-125 and 2-3 weeks for palladium-103 1
• Task Group 43 (TG-43) dosimetric parameters should be used for dose calculations 1

Isotope selection:

• Either iodine-125 or palladium-103 may be used (no evidence favoring one over the other) 1
• For temporary implants, iridium is the standard isotope 1

Advantages Over Other Modalities

Compared to radical prostatectomy:

• Treatment completed in single day with minimal time away from normal activities 1
• Minimal incontinence risk in patients without prior TURP 1
• Short-term erectile function preservation superior 1
• No surgical complications (bleeding, anesthesia risks) 1

Compared to external beam radiation:

• Single-day treatment versus 8-9 weeks of daily treatments 1
• Delivers higher biologically equivalent dose to prostate (approximately 2x that of external beam) 5
• Superior dose conformality with minimal bladder and rectal exposure 1

Disadvantages and Side Effects

Urinary complications:

• Irritative voiding symptoms commonly persist for up to 1 year after implantation 1
• Risk of acute urinary retention requiring catheterization 1
• Brachytherapy exacerbates urinary obstructive symptoms more than external beam radiation 1, 3
• Incontinence risk significantly elevated in patients with prior TURP 1

Sexual function:

• Progressive erectile dysfunction develops over several years (not immediate like surgery) 1
• Similar erectile dysfunction rates as external beam radiation therapy 1

Other considerations:

• Requires general anesthesia 1
• Proctitis rates similar to external beam radiation 1
• Patients must follow radioprotective measures: avoid close contact with children and pregnant women, use condoms, filter urine, inform physicians before pelvic interventions 1

Critical Pitfalls to Avoid

Do NOT use brachytherapy with temporary implants for stage T1 or T2a tumors outside of randomized clinical trials 1

Retropubic brachytherapy should no longer be used (transperineal approach is standard) 1

Do NOT omit postimplantation dosimetry - this is essential for quality assurance and must be performed at specified intervals 1

Do NOT use brachytherapy monotherapy for high-risk disease - requires combination with external beam radiation and ADT 1, 3

Avoid brachytherapy in patients with significant baseline urinary symptoms - these will be substantially worsened 1

Long-Term Outcomes

Biochemical control rates:

• Low-risk: >85% at 5 years, 67-87% at 10-15 years 4, 6
• Intermediate-risk: 69-97% at 5 years 4
• High-risk (with EBRT + ADT): 63-80% at 5 years 4

Survival outcomes:

• 10-year overall survival >85% 4
• 10-year cancer-specific mortality <5% 4
• 10-year distant metastasis rate <10% 4

Quality of life:

• Grade 3-4 toxicities rare (<4% in most series) 4
• Quality of life improved compared to surgery 4