What is the role of brachytherapy in cancer treatment?

Role of Brachytherapy in Cancer Treatment

Brachytherapy is a critical component of cancer treatment that delivers highly conformal radiation directly to tumors while minimizing exposure to surrounding tissues, making it an essential treatment modality for various cancers including prostate, cervical, endometrial, breast, and head and neck cancers. 1, 2

What is Brachytherapy?

Brachytherapy is a specialized form of radiotherapy that involves placing radioactive sources directly into or adjacent to tumor tissue. This approach offers several advantages:

• Delivers high radiation doses precisely to the tumor
• Minimizes radiation exposure to surrounding healthy tissues
• Allows for shorter overall treatment time compared to external beam radiation
• Provides rapid dose fall-off beyond the target area 2

Types of Brachytherapy

Low-Dose-Rate (LDR) Brachytherapy

• Involves permanent implantation of radioactive seeds (typically iodine-125 or palladium-103)
• Seeds gradually lose radioactivity over time
• Commonly used for low-risk prostate cancer
• Treatment completed in one day with minimal disruption to normal activities 1, 2

High-Dose-Rate (HDR) Brachytherapy

• Involves temporary insertion of a radiation source
• Often used as a "boost" in addition to external beam radiation therapy (EBRT)
• Common boost regimens include 9.5-11.5 Gy × 2 fractions, 5.5-7.5 Gy × 3 fractions
• Can be used as monotherapy in select cases (13.5 Gy × 2 fractions) 1, 2

Applications by Cancer Type

Prostate Cancer

• Low-risk disease: Brachytherapy alone is appropriate for patients with cT1c-T2a, Gleason grade 2-6, PSA <10 ng/mL
• Intermediate-risk disease: Can be combined with EBRT (40-50 Gy) with or without androgen deprivation therapy (ADT)
• High-risk disease: Previously considered unsuitable for brachytherapy alone, but trimodality treatment (brachytherapy + EBRT + ADT) shows excellent outcomes with 9-year progression-free survival and disease-specific survival of 87% and 91%, respectively 1, 2

Cervical Cancer

• Essential component of definitive therapy for patients with primary cervical cancer who are not surgical candidates
• Usually performed using an intracavitary approach with intrauterine tandem and vaginal colpostats
• Typically initiated during the latter part of EBRT when sufficient tumor regression allows for optimal applicator placement
• In rare cases where intracavitary approach is not feasible, interstitial brachytherapy may be used 1

Outcomes and Effectiveness

Brachytherapy demonstrates excellent cancer control rates:

• 5-year biochemical relapse-free survival rates for prostate cancer: 95% (low-risk), 84% (intermediate-risk), and 81% (high-risk) 1, 2
• For low-risk prostate tumors, cancer control rates appear comparable to surgery (>90%) with medium-term follow-up 1
• Trimodality treatment for high-risk prostate cancer shows 9-year progression-free survival of 87% 1, 2

Patient Selection Considerations

Ideal Candidates

• Patients with appropriately sized prostates for prostate brachytherapy
• No previous transurethral resection of the prostate (TURP)
• Low to intermediate risk disease profiles 1, 2

Relative Contraindications

• Very large or very small prostates
• High International Prostate Symptom Score (significant bladder outlet obstruction)
• Previous TURP (increased risk of incontinence)
• Prior pelvic irradiation
• Active inflammatory disease of the rectum 1, 2

Side Effects and Complications

• Requires general anesthesia for procedure
• Risk of acute urinary retention
• Irritative voiding symptoms may persist for up to 1 year after implantation
• Higher risk of incontinence in patients with previous TURP
• Progressive erectile dysfunction may develop over several years
• Rectal symptoms from radiation proctitis (low but definite risk) 1, 2

Current Challenges in Brachytherapy

• Declining utilization for both prostate and gynecologic malignancies over the past 20 years
• Uneven distribution of brachytherapy facilities globally, with fewer resources in regions with highest cervical cancer incidence
• Logistical challenges, lower reimbursement, and inadequate training contributing to preference for external beam techniques 3, 4

Quality Assurance

• Postimplant dosimetry should be performed to document the quality of the implant
• For prostate cancer, recommended prescribed doses for monotherapy are 145 Gy for 125Iodine and 125 Gy for 103Palladium
• After 40-50 Gy external-beam RT, the corresponding boost doses are 110 and 100 Gy, respectively 1, 2

Brachytherapy remains an irreplaceable component of modern cancer treatment, offering unique advantages in dose delivery and tissue sparing that cannot be fully replicated by external beam techniques. Despite challenges in maintaining expertise and access, its role in improving outcomes for patients with various cancers is well-established and supported by high-quality evidence.