What type of treatment involves placing radioactive elements directly into the prostate to treat prostate cancer?

Brachytherapy for Prostate Cancer Treatment

Brachytherapy is the type of treatment used to treat prostate cancer by placing radioactive elements directly into the prostate tissue. 1

Types of Prostate Brachytherapy

There are two main methods of prostate brachytherapy:

Low Dose Rate (LDR) Brachytherapy

• Involves permanent implantation of radioactive seeds (typically iodine-125 or palladium-103) into the prostate tissue 1
• Seeds gradually lose their radioactivity over time
• Treatment is completed in one day with minimal disruption to normal activities 1
• Recommended prescribed doses for monotherapy: 145 Gy for iodine-125 and 125 Gy for palladium-103 1

High Dose Rate (HDR) Brachytherapy

• Involves temporary insertion of a radiation source into the prostate 1
• Often used as a "boost" dose in addition to external beam radiation therapy (EBRT)
• Common boost dose regimens include:
  • 9.5-11.5 Gy × 2 fractions
  • 5.5-7.5 Gy × 3 fractions
  • 4.0-6.0 Gy × 4 fractions 1
• HDR monotherapy regimen: 13.5 Gy × 2 fractions 1

Mechanism and Benefits

Brachytherapy works by delivering radiation directly to the cancer within the prostate while minimizing exposure to surrounding tissues:

• The short range of radiation from low-energy sources allows adequate dose delivery to the prostate while avoiding excessive irradiation of the bladder and rectum 1
• Current techniques focus on improving radioactive seed placement and radiation dose distribution 1
• Cancer control rates appear comparable to radical prostatectomy (>90%) for low-risk tumors 1
• HDR brachytherapy demonstrates the most favorable toxicity profile with lower risks of urinary frequency, urgency, rectal pain, and erectile dysfunction compared to other radiation modalities 2

Patient Selection

Ideal Candidates for LDR Brachytherapy Monotherapy

• Low-risk prostate cancer (cT1c-T2a, Gleason grade 2-6, PSA <10 ng/mL) 1
• No previous transurethral resection of the prostate (TURP) 1
• Appropriately sized prostate (not very large or very small) 1
• No significant bladder outlet obstruction symptoms 1

Candidates for Combined Therapy

• Intermediate-risk cancers: Brachytherapy may be combined with EBRT (45 Gy) with or without neoadjuvant ADT 1
• High-risk cancers: Traditionally considered poor candidates for permanent brachytherapy alone, but may benefit from combination of EBRT, brachytherapy, and ADT 1

Potential Side Effects and Complications

• General anesthesia requirement 1
• Risk of acute urinary retention 1
• Irritative voiding symptoms may persist for up to 1 year after implantation 1
• Higher risk of incontinence in patients with previous TURP 1
• Progressive erectile dysfunction may develop over several years 1
• Rectal symptoms from radiation proctitis (low but definite risk) 1

Contraindications

• Prior pelvic irradiation 1
• Active inflammatory disease of the rectum 1
• Permanent indwelling Foley catheter 1
• Very large or very small prostates 1
• High International Prostate Symptom Score (significant bladder outlet obstruction) 1
• Previous TURP (relative contraindication) 1

Treatment Outcomes

• For low-risk disease: 5-year biochemical relapse-free survival rate of 95% 1
• For intermediate-risk disease: 5-year biochemical relapse-free survival rate of 84% 1
• For high-risk disease: 5-year biochemical relapse-free survival rate of 81% 1
• Trimodality treatment (brachytherapy + EBRT + ADT) shows excellent outcomes with 9-year progression-free survival and disease-specific survival reaching 87% and 91%, respectively 1

Important Considerations

• Postimplant dosimetry should be performed to document the quality of the implant 1
• Neoadjuvant ADT may be used to shrink the prostate to an acceptable size for implantation, but may increase toxicity 1
• IMRT causes less acute and late genitourinary toxicity compared with permanent seed implants while maintaining similar freedom from biochemical failure 1

Brachytherapy represents one of the oldest techniques for treating prostate cancer and continues to evolve with new radioactive isotopes, improved afterloading techniques, and better understanding of radiobiology associated with different dose rates 3.