Brachytherapy treats prostate cancer by placing a sealed radiation source directly inside the prostate rather than sending the full treatment dose through the body from an external machine. Low-dose-rate (LDR) brachytherapy leaves small radioactive seeds permanently in the prostate, where their radiation gradually decays. High-dose-rate (HDR) brachytherapy temporarily places treatment catheters through the perineum into the prostate; a high-activity source travels through those catheters for a planned period and is then removed. Brachytherapy can be used alone in selected favorable localized cancers or as a dose-intensifying boost with external-beam radiation in selected higher-risk disease.
Brachytherapy is an internal radiation treatment that creates a very high prostate dose while the radiation falls off rapidly outside the gland. LDR uses permanent seeds; HDR uses temporary catheters and leaves no radioactive source behind after treatment. The strongest candidates generally have localized prostate cancer, a prostate anatomy suitable for implantation and good baseline urinary function. Current EAU guidance defines favorable urinary selection for LDR monotherapy with an IPSS below 12 and a maximum urinary flow rate above 15 mL/s. Brachytherapy is not automatically preferable to EBRT or surgery: its major trade-off is excellent local dose concentration versus a higher risk of urinary irritation, retention or urethral stricture in susceptible patients.
01What Is Prostate Brachytherapy and How Do LDR and HDR Differ?
Brachytherapy places the radiation source inside the treatment target
“Brachy” means short distance.
Instead of delivering all radiation from outside the pelvis, brachytherapy places sealed radioactive material directly in or immediately next to the prostate cancer.
That physical arrangement allows:
- a high radiation dose inside the prostate;
- steep dose fall-off outside the gland;
- less exposure to distant normal tissues;
- and highly localized dose escalation.
It does not eliminate exposure to the urethra, bladder neck or rectal wall because those structures sit within or immediately next to the prostate.
What is LDR brachytherapy?
Low-dose-rate brachytherapy uses small sealed radioactive seeds that are placed permanently inside the prostate.
Common isotopes include iodine-125 and palladium-103.
The seeds:
- remain physically in the prostate;
- release radiation continuously at a low rate;
- lose radioactivity progressively;
- and generally do not need to be removed.
The goal is to position enough seeds to cover the prostate target while limiting excessive urethral and rectal dose.
What is HDR brachytherapy?
High-dose-rate brachytherapy uses temporary hollow catheters inserted through the perineum into the prostate.
The patient is connected to a remote afterloader containing a high-activity radiation source.
The source moves through each catheter and pauses at programmed positions called dwell positions.
The treatment computer controls:
- which catheter positions are used;
- how long the source stays at each position;
- and therefore how the final radiation dose is shaped.
After the planned treatment is delivered, the radioactive source returns to the shielded afterloader. The catheters are removed after the required fraction or treatment course.
No radioactive material remains inside the patient after HDR treatment is complete.
Is brachytherapy the same as radiopharmaceutical therapy?
No.
Brachytherapy uses a sealed radiation source placed locally inside the prostate.
Radiopharmaceutical therapy is systemic: a radioactive drug travels through the bloodstream and targets cancer cells or tissues elsewhere in the body.
Is brachytherapy surgery?
It is an invasive procedure, but it is not prostate-removal surgery.
The prostate remains in place.
The procedure generally requires anesthesia because multiple needles or catheters must pass through the perineum into the gland.
The central difference is permanence of the source. LDR leaves the seeds in place; HDR removes the source and catheters after treatment. Both rely on precise prostate geometry and dose planning.
02Who Is a Candidate for Prostate Brachytherapy?
Cancer risk and urinary anatomy both matter
Brachytherapy selection is different from deciding whether radiation is possible at all.
A patient may be an excellent radiation candidate but a poor implant candidate because of:
- severe urinary obstruction;
- very poor urinary flow;
- large or anatomically difficult prostate geometry;
- prior procedures that distort the urethra or gland;
- or medical factors that make anesthesia or transperineal implantation unsafe.
Which cancers can be treated with brachytherapy alone?
AUA/ASTRO guidance recognizes permanent LDR seed implantation and temporary HDR prostate implantation as accepted definitive options for patients with low- or favorable intermediate-risk localized prostate cancer who choose radiation treatment.
Current EAU guidance specifically recommends LDR brachytherapy for favorable intermediate-risk disease when urinary function is good.
For low-risk disease, the first question remains whether treatment is needed at all because active surveillance is often preferred.
How is “good urinary function” defined?
The current EAU treatment guideline gives a practical LDR selection definition:
- International Prostate Symptom Score (IPSS) below 12;
- maximum urinary flow rate above 15 mL/s.
These are useful selection markers rather than universal laws.
A treatment centre can consider additional information such as:
- post-void residual urine;
- prostate volume;
- median lobe anatomy;
- history of retention;
- urethral stricture;
- prior TURP;
- and whether the pubic arch obstructs needle access.
Why do urinary symptoms matter so much?
Brachytherapy irradiates the prostate from inside the gland.
The prostatic urethra is therefore surrounded by the treatment target.
Temporary swelling and radiation inflammation can further narrow the urinary channel after implantation.
A patient who already has poor flow or severe obstruction has less reserve and is more likely to develop:
- acute urinary retention;
- prolonged irritative symptoms;
- or later urethral complications.
Is a large prostate an absolute contraindication?
No.
Prostate size changes:
- the number and position of needles or seeds;
- pubic-arch access;
- urethral dose;
- and post-implant swelling.
Large glands can still be treated in experienced centres, but the technical difficulty and urinary risk can be higher.
Hormonal therapy is sometimes used to shrink a large gland before implantation, although that is a procedural downsizing strategy rather than proof that ADT is oncologically necessary for a favorable-risk tumor.
Can someone with a previous TURP have brachytherapy?
Previous TURP is not an automatic exclusion.
Current EAU guidance states that brachytherapy can be performed after TURP when dose distribution and residual prostate tissue are suitable.
The guideline recommends careful technique and adequate healing time; in the specific minimal-channel TURP context described by EAU, at least a three-month interval before brachytherapy is recommended.
What other health factors matter?
The team also evaluates:
- ability to undergo anesthesia;
- anticoagulant or antiplatelet therapy;
- bleeding risk;
- infection risk;
- hip mobility and ability to tolerate lithotomy positioning;
- inflammatory bowel disease or prior pelvic radiation;
- and overall life expectancy and competing illness.
How should a commercial brachytherapy program be evaluated?
Brachytherapy is highly operator dependent.
EAU explicitly notes a learning curve and recommends that implantation be performed by teams experienced in transrectal ultrasound and transperineal procedures with robust audit reporting.
Useful questions for a treatment centre include:
- How many prostate LDR or HDR implants does the team perform each year?
- Which risk groups do they routinely treat with monotherapy versus boost?
- What urinary criteria are used to exclude or modify treatment?
- How are prostate volume and pubic-arch interference assessed?
- Is real-time or post-implant dosimetry audited?
- What are the centre’s urinary-retention and urethral-stricture rates?
- How often is a catheter needed beyond the planned period?
- How are dose constraints for urethra and rectum monitored?
- For higher-risk disease, how are EBRT and ADT integrated?
- Who manages urinary symptoms after the implant?
Brachytherapy is unusually dependent on both cancer biology and plumbing. A favorable tumor does not automatically make someone a good seed candidate if the urinary outlet is already severely compromised.
03How Is Low-Dose-Rate Seed Brachytherapy Performed?
The prostate is mapped and implanted through the perineum
LDR implantation is usually performed under general or spinal anesthesia.
A typical procedure includes:
- positioning the patient with access to the perineum;
- placing a transrectal ultrasound probe;
- mapping the prostate and nearby structures;
- positioning a template grid against the perineum;
- advancing implant needles into predefined prostate coordinates;
- depositing radioactive seeds according to the dose plan;
- checking seed geometry and urinary tract integrity;
- and removing the implant needles while the seeds remain behind.
How big are the seeds?
The sealed sources are very small—roughly comparable to a grain or seed.
The exact number implanted depends on:
- prostate volume;
- isotope;
- source strength;
- prescription dose;
- and the geometry required to cover the target.
A fixed seed count should therefore not be used as a quality measure.
What happens to the seeds after treatment?
They stay in the prostate permanently.
The radioactive material loses activity over time until the residual radiation becomes negligible.
The inactive seed capsules generally remain in place without needing surgical removal.
Is the patient radioactive after an LDR implant?
A permanent LDR implant gives off a small amount of radiation for a period after treatment.
NCI advises that patients with permanent implants may need temporary precautions around other people, especially pregnant people and young children, depending on the source and treatment plan.
Specific instructions should come from the treating radiation-safety team because the required precautions depend on:
- which isotope was used;
- source strength;
- implant geometry;
- and local radiation-safety rules.
Can a seed come out?
Seed loss is uncommon but possible.
Some centres give instructions to strain urine briefly after implantation or use temporary sexual precautions because a seed can rarely be passed in urine or semen.
If a seed is found, it should be handled according to the radiation-safety instructions from the treatment centre rather than picked up casually.
What is recovery like after seed implantation?
Common early effects include:
- perineal bruising or tenderness;
- blood in the urine;
- blood in the semen;
- urinary frequency;
- urgency;
- burning;
- weaker stream;
- and temporary difficulty emptying the bladder.
Urinary symptoms often become more noticeable over the first several weeks as swelling and radiation irritation develop, then improve gradually over subsequent months.
Can acute urinary retention occur?
Yes.
A small proportion of patients can become unable to urinate and need temporary catheter drainage.
Risk rises with worse baseline urinary symptoms, larger prostate volume and greater obstructive anatomy.
What is post-implant dosimetry?
After LDR implantation, CT or other imaging can be used to reconstruct the final seed positions and calculate the radiation dose actually delivered to:
- the prostate;
- urethra;
- rectum;
- and surrounding tissues.
This is an important quality-control step because the delivered implant can differ from the pre-implant plan.
LDR quality is not measured by how many seeds were used. The meaningful question is whether the final implant achieved adequate target coverage while respecting urethral and rectal dose constraints.
04How Does HDR Brachytherapy Work, and When Is Brachytherapy Used as a Boost?
HDR uses temporary catheters and a remote afterloader
HDR implantation also uses transperineal access under anesthesia.
Instead of depositing permanent seeds, the radiation oncologist places hollow treatment catheters through the perineum into the prostate.
Imaging is then used to reconstruct:
- the prostate;
- each catheter path;
- the urethra;
- rectum;
- bladder;
- and sometimes a dominant tumor target.
What is remote afterloading?
The catheters themselves are not radioactive.
During treatment, a shielded machine sends a high-activity source into each catheter.
The source stops at programmed dwell positions for calculated amounts of time.
Changing the dwell time and positions allows the team to sculpt a high radiation dose through the prostate without permanently implanting material.
Is someone radioactive after HDR treatment?
No.
Once the source has returned to the afterloader, there is no radioactive source left inside the body.
NCI states that after a temporary brachytherapy source and applicator are removed, it is safe for others—including children and pregnant people—to be near the patient.
Can HDR be used without EBRT?
Yes, in selected patients.
EAU notes that fractionated HDR monotherapy can be offered to selected intermediate-risk patients in very experienced centres, while also emphasizing that the evidence base is smaller than for more established LDR monotherapy and EBRT strategies.
EAU reports five-year PSA control above 90% in these experienced-centre series, with late grade 3 or higher urinary toxicity below 5% and minimal severe gastrointestinal toxicity.
What is a brachytherapy boost?
A boost combines:
- EBRT to the prostate and selected surrounding tissues;
- plus an additional concentrated LDR or HDR dose inside the prostate.
The goal is to increase local tumor dose beyond what EBRT alone can safely deliver to the whole pelvic anatomy.
Who is considered for a brachytherapy boost?
Current EAU guidance allows:
- LDR or HDR boost for selected unfavorable intermediate-risk patients with good urinary function, combined with EBRT and short-term ADT;
- LDR or HDR boost for selected high-risk patients with good urinary function, combined with EBRT and long-term ADT;
- and selected locally advanced patients as part of multimodal treatment.
The next page in this management chain covers Androgen Deprivation Therapy for Prostate Cancer.
Does adding EBRT to brachytherapy improve intermediate-risk outcomes?
Not automatically.
NRG Oncology RTOG 0232 randomized 588 men with intermediate-risk prostate cancer to:
- brachytherapy alone;
- or EBRT followed by a brachytherapy boost.
At five years, there was no statistically significant improvement in freedom from progression with the combination.
Using the Phoenix biochemical definition:
- five-year freedom from progression was 88.0% with EBRT + brachytherapy;
- versus 85.5% with brachytherapy alone.
But late grade 2 or higher GU/GI toxicity was:
- 42.8% with combination treatment;
- versus 25.8% with brachytherapy alone.
Late grade 3 or higher toxicity was 8.2% versus 3.8%.
The trial therefore supports brachytherapy alone as a standard option for appropriately selected intermediate-risk patients rather than assuming EBRT must always be added.
What about higher-risk disease?
ASCENDE-RT tested a different question in an intermediate- and high-risk population, most of whom had high-risk disease.
All patients received:
- 12 months of ADT;
- pelvic EBRT;
- then either an EBRT dose-escalation boost or an LDR brachytherapy boost.
At approximately 10 years, time to biochemical progression favored the LDR boost:
- 85% with LDR brachytherapy boost;
- versus 67% with the dose-escalated EBRT boost.
However, that improvement did not translate into a statistically significant overall-survival or distant-metastasis advantage in the updated analysis.
The stronger local dose also came with more severe urinary toxicity. EAU summarizes late grade 3 or higher genitourinary toxicity at approximately:
- 18% with the LDR boost;
- versus 8% with the EBRT boost.
What is the correct interpretation of those two trials?
They answer different clinical questions.
RTOG 0232 shows that adding EBRT to brachytherapy in an intermediate-risk population can add toxicity without improving progression control.
ASCENDE-RT shows that in a more aggressive risk population already receiving pelvic EBRT and ADT, an LDR boost can intensify biochemical control—but at a significant urinary cost.
Brachytherapy boost is dose escalation, not automatically “better radiation.” In higher-risk disease it can improve biochemical control, but the urinary toxicity trade-off is real and should be discussed explicitly.
05What Are the Side Effects, PSA Changes and Long-Term Outcomes After Brachytherapy?
Urinary effects are the dominant early trade-off
Because the urethra passes directly through the implanted prostate, urinary symptoms are common after both LDR and HDR procedures.
Possible early symptoms include:
- frequency;
- urgency;
- nocturia;
- burning;
- slower urinary flow;
- sensation of incomplete emptying;
- and temporary urinary retention.
Alpha-blocker medication is often used around the treatment period to reduce obstructive and irritative symptoms.
What late urinary complications can occur?
Late complications can include:
- persistent lower urinary tract symptoms;
- urethral stricture;
- hematuria;
- urinary retention requiring a procedure;
- and, less commonly, urinary incontinence.
Risk rises when baseline urinary function is poor or when treatment is intensified with combined EBRT and brachytherapy boost.
What bowel effects can occur?
Brachytherapy usually exposes less rectal volume than broad external-beam fields, but the posterior prostate sits immediately beside the rectal wall.
Possible effects include:
- rectal urgency;
- discomfort;
- minor bleeding;
- or chronic radiation proctitis in a minority of patients.
How does brachytherapy affect erections?
Erectile function can decline gradually after treatment.
The risk depends on:
- age;
- erectile function before treatment;
- vascular health;
- radiation dose to neurovascular and penile structures;
- and whether EBRT or ADT is added.
Unlike radical prostatectomy, brachytherapy does not remove the prostate or seminal vesicles, so ejaculation can persist, although semen volume, fertility and ejaculatory function can change.
How does PSA behave after brachytherapy?
The prostate remains in place.
PSA therefore:
- declines gradually rather than immediately becoming undetectable;
- can take years to reach its lowest value;
- and can show a temporary PSA bounce before declining again.
A PSA bounce is particularly well recognized after prostate brachytherapy and does not automatically mean recurrence.
How is biochemical recurrence defined?
As with other definitive radiation treatments, the classic Phoenix definition uses:
PSA nadir + 2 ng/mL.
A concerning PSA pattern can still justify earlier imaging or investigation when the result would change management.
What does brachytherapy achieve in favorable localized disease?
Long-term observational series report high biochemical control in appropriately selected low- and intermediate-risk patients.
A large long-term cohort of 1,457 patients treated mainly with brachytherapy alone reported:
- 93.2% biochemical progression-free survival at 10 years;
- 89.2% at 15 years.
Those numbers come from a retrospective cohort rather than a randomized comparison and should not be applied as an individual prediction.
Can brachytherapy be used after cancer recurs following prior radiation?
Yes, but this is a specialized salvage setting.
EAU considers carefully selected patients with:
- good performance status;
- originally localized disease;
- good urinary function;
- and biopsy-proven local recurrence;
potential candidates for salvage HDR or LDR brachytherapy in experienced centres.
The toxicity risk is higher because normal pelvic tissues have already been irradiated.
Outcome statistics should be read in context. A favorable-risk LDR monotherapy cohort, an intermediate-risk randomized trial and a high-risk brachytherapy-boost trial are different populations and cannot be ranked by raw PSA-control percentages alone.
→LDR vs HDR Brachytherapy at a Glance
| Feature | LDR brachytherapy | HDR brachytherapy |
|---|---|---|
| Radiation source | Multiple small sealed seeds. | One high-activity source moved through temporary catheters. |
| Source permanence | Seeds remain permanently in prostate. | Source is completely removed after treatment. |
| Dose delivery | Continuous low-dose emission over time. | High dose delivered over programmed dwell positions during treatment. |
| Implant guidance | TRUS + transperineal template / needles. | Imaging + transperineal catheter reconstruction. |
| Radiation precautions afterward | Temporary source-specific precautions may be required. | No retained radioactivity after source/catheters are removed. |
| Monotherapy role | Established option for appropriately selected favorable localized disease. | Used as monotherapy in selected patients, particularly in experienced centres. |
| Boost role | Can be combined with EBRT for selected unfavorable intermediate/high-risk disease. | Can also be combined with EBRT for dose intensification. |
| Main functional limitation | Urinary irritation/obstruction, retention and late urethral toxicity. | Similar urinary concern; toxicity depends on dose, fractionation and catheter geometry. |
| Quality metric | Final implant dosimetry and clinical outcomes—not seed count. | Target coverage, dwell optimization, constraints and audited outcomes. |
Key Points
- Brachytherapy is internal radiation placed directly inside or next to the prostate tumor target.
- LDR brachytherapy leaves permanent radioactive seeds in the prostate.
- HDR brachytherapy uses temporary catheters and removes the radioactive source completely after treatment.
- Both techniques usually require anesthesia and transperineal access.
- Transrectal ultrasound is commonly used to define the prostate and guide implantation.
- Good baseline urinary function is central to brachytherapy selection.
- EAU defines a practical favorable LDR urinary profile as IPSS <12 and maximum urinary flow >15 mL/s.
- Large prostate volume is not an automatic exclusion but can increase technical and urinary difficulty.
- Previous TURP is not an absolute contraindication when anatomy, healing and dose distribution are appropriate.
- LDR monotherapy is an established definitive radiation option for appropriately selected favorable localized disease.
- HDR monotherapy can be used in selected patients at experienced centres, but its evidence base is smaller.
- Unfavorable intermediate- and high-risk disease can use LDR or HDR as a boost with EBRT and risk-appropriate ADT.
- NRG/RTOG 0232 found no progression benefit from adding EBRT to brachytherapy in its intermediate-risk population, while late toxicity increased.
- ASCENDE-RT found better 10-year biochemical control with an LDR boost in a higher-risk population but substantially more severe urinary toxicity.
- Urinary frequency, urgency, weak flow and temporary retention are common early trade-offs.
- Late urethral stricture and other genitourinary toxicity are important risks, particularly after intensified combination treatment.
- Permanent LDR implants can require temporary radiation-safety precautions; the treatment centre should provide individualized instructions.
- HDR patients are not radioactive after the source and catheters are removed.
- PSA falls gradually after brachytherapy and may temporarily bounce.
- The classic radiation biochemical-recurrence threshold remains PSA nadir + 2 ng/mL.
Clinical bottom line: brachytherapy is one of the most concentrated ways to deliver prostate radiation because the source is placed inside the gland. LDR treatment permanently implants low-activity seeds; HDR temporarily inserts catheters and moves a high-activity source through planned positions before removing it completely. The procedure is most attractive when the cancer risk matches the intended role of the implant and urinary function is good enough to tolerate swelling and urethral radiation. Favorable localized disease can be treated with brachytherapy alone in selected patients, while unfavorable intermediate- and high-risk disease can use brachytherapy as a dose-escalating boost with EBRT and ADT. The trade-off is important: higher intraprostatic dose can improve biochemical control, but urinary retention, irritation and late urethral toxicity can increase. Technique, patient selection and implant-team experience therefore matter as much as whether the source is labeled LDR or HDR.
Medical disclaimer: This article provides general medical education about prostate brachytherapy. Implant suitability, LDR versus HDR selection, urinary thresholds, prostate-volume constraints, prior-TURP eligibility, isotope, dose, fractionation, use of EBRT, ADT, anesthesia and radiation-safety precautions vary according to cancer risk, anatomy, urinary function, medications, comorbidity and treatment-centre expertise. Individual treatment should be planned with a radiation oncologist and multidisciplinary prostate-cancer team.
For the full radiation framework, return to Radiation Therapy for Prostate Cancer. The preceding modality guide covers External Beam Radiation Therapy. The next management guide covers Androgen Deprivation Therapy for Prostate Cancer. For the overall treatment sequence, review Prostate Cancer Treatment. Long-term urinary, sexual and PSA follow-up is covered in Prostate Cancer Survivorship.
Evidence Sources
- European Association of Urology — Prostate Cancer Treatment: current LDR/HDR indications, urinary-function selection, TURP considerations, monotherapy, brachytherapy boost, ADT combinations and toxicity.
- European Association of Urology — Prostate Cancer Follow-up: follow-up after LDR/HDR brachytherapy and PSA-based recurrence principles after curative radiation.
- AUA/ASTRO — Clinically Localized Prostate Cancer Guideline: LDR and HDR brachytherapy as definitive radiation options and risk-adapted combination therapy.
- National Cancer Institute — Brachytherapy to Treat Cancer: permanent versus temporary implants, catheter/applicator concepts and radiation-safety principles.
- National Cancer Institute — Prostate Cancer Treatment PDQ, Patient Version: prostate seed implantation, image guidance and role of internal radiation in localized disease.
- NRG Oncology RTOG 0232 randomized trial — brachytherapy alone versus EBRT plus brachytherapy for intermediate-risk disease, including freedom-from-progression and toxicity outcomes.
- ASCENDE-RT updated 10-year analysis — LDR brachytherapy boost versus dose-escalated EBRT boost for intermediate/high-risk prostate cancer.
- Long-term brachytherapy cohort — 10- and 15-year biochemical progression-free survival after prostate brachytherapy in low/intermediate-risk disease.
