Prostate Cancer Seed Implant: LDR Brachytherapy, Benefits, Side Effects & Who Qualifies

What Is Prostate Brachytherapy?

Brachytherapy is radiation delivered from inside or immediately next to the prostate.

This allows a high radiation dose to the prostate while limiting exposure to surrounding tissues such as the rectum and bladder.

There are two main forms:

What Is LDR “Seed Implant” Brachytherapy?

LDR brachytherapy is the treatment most people mean when they talk about prostate cancer seed implants.

Very small radioactive seeds—about the size of grains of rice—are inserted through thin needles passed through the perineum, the skin between the scrotum and anus.

Transrectal ultrasound and computerized treatment planning help the team position the seeds throughout the prostate.

The seeds remain in place permanently, but the radioactive material gradually decays until the seeds no longer deliver a meaningful radiation dose.

How Many Seeds Are Implanted?

There is no fixed number.

The legacy version of this page stated that 40–60 seeds are usually used. That can be too low for many contemporary implants.

The exact number depends on:

• prostate size;
• the isotope used;
• prescribed dose;
• seed strength;
• treatment-planning technique; and
• the individual anatomy.

Some implants use around 70–100 seeds or more, while others use fewer. The important issue is not the seed count itself but whether the planned radiation dose adequately covers the prostate while protecting the urethra, rectum and bladder.

Which Radioactive Seeds Are Used?

Current LDR prostate brachytherapy may use:

• iodine-125 (I-125) — the most common isotope;
• palladium-103 (Pd-103); or
• cesium-131 (Cs-131) in some centers.

These isotopes have different half-lives and dose-delivery characteristics, but all are designed to deliver highly localized radiation inside the prostate.

Who Is a Good Candidate for Seed Implant Brachytherapy?

The old page restricted treatment almost entirely to men with:

• PSA below 10 ng/mL;
• Gleason score 6 or less; and
• a tumor fully contained within the prostate.

Those criteria are now too narrow.

Current guidance makes the decision based on the patient’s overall risk group and urinary function.

Low-Risk Prostate Cancer

When definitive radiation treatment is chosen, permanent LDR seed implantation is an established treatment option for appropriately selected low-risk patients.

However, many men with low-risk disease are better candidates for active surveillance and may not need immediate treatment.

Favorable Intermediate-Risk Prostate Cancer

Current EAU guidance strongly supports LDR brachytherapy for men with favorable intermediate-risk disease who have good urinary function.

The guideline uses examples such as:

• IPSS below 12; and
• maximum urinary flow rate above 15 mL/second.

The 2022 AUA/ASTRO guideline similarly recognizes permanent LDR seed implantation and temporary HDR implantation as appropriate radiation options for low- or favorable intermediate-risk localized prostate cancer.

What About Unfavorable Intermediate-Risk Prostate Cancer?

Brachytherapy can still play an important role, but treatment is often more intensive.

Current EAU guidance allows consideration of:

• external-beam IMRT/VMAT;
• LDR or HDR brachytherapy boost; and
• short-term ADT for approximately 4–6 months.

The goal of the brachytherapy boost is to deliver a very high biological radiation dose inside the prostate.

Can Brachytherapy Be Used for High-Risk Prostate Cancer?

Yes, in selected men—but generally as part of combined treatment rather than as seed implantation alone.

For men with high-risk localized disease and good urinary function, current EAU guidance allows:

external-beam radiation + LDR or HDR brachytherapy boost + long-term ADT.

Long-term ADT is generally given for approximately 2–3 years in this setting.

This is substantially different from the old idea that seed implantation is only for a small, non-aggressive tumor.

Does Brachytherapy Improve Cancer Control?

Brachytherapy can provide excellent long-term biochemical control in appropriately selected patients.

For unfavorable intermediate- and high-risk disease, adding an LDR brachytherapy boost can improve PSA-based disease control compared with external-beam radiation alone.

However, that improvement comes at the cost of more urinary toxicity.

In the ASCENDE-RT randomized trial, the LDR boost improved long-term PSA progression-free outcomes, but late severe genitourinary toxicity was higher.

What Is HDR Brachytherapy?

HDR brachytherapy does not leave radioactive seeds inside the prostate.

Instead:

1. thin catheters are placed temporarily through the perineum into the prostate;
2. a computer-controlled radioactive source—usually iridium-192—is moved through those catheters;
3. the source delivers a high radiation dose over several minutes; and
4. the radioactive source is removed completely.

The catheters are removed after the planned treatment session or sessions.

Once the radioactive source is removed, the patient is not radioactive.

Can HDR Brachytherapy Be Used Alone?

Fractionated HDR monotherapy can be offered to selected patients with intermediate-risk disease at experienced centers.

However, current EAU guidance notes that evidence comes from relatively limited series.

Importantly, single-fraction HDR monotherapy should not be used because long-term biochemical control has been inferior to fractionated HDR schedules.

How Is an LDR Seed Implant Procedure Performed?

Although exact techniques vary, a typical procedure includes:

1. pre-treatment assessment and imaging;
2. anesthesia—general or spinal/neuraxial depending on the center;
3. placement of an ultrasound probe in the rectum;
4. computerized mapping of the prostate;
5. insertion of hollow needles through the perineum;
6. placement of radioactive seeds according to the treatment plan;
7. verification of implant position; and
8. recovery before discharge.

A radiation oncologist, physicist and often a urologist work as part of the brachytherapy team.

Is General Anesthesia Always Required?

No.

Many procedures are performed under general anesthesia, but spinal or other regional anesthesia may also be used.

The choice depends on the center, patient health and procedural approach.

How Long Does the Procedure Take?

The implant itself commonly takes roughly 1–2 hours, although total time in the treatment facility is longer because of anesthesia, preparation, imaging and recovery.

Many patients go home the same day or after a short observation period.

What Tests Are Needed Before Brachytherapy?

Assessment commonly includes:

• PSA;
• biopsy Grade Group/Gleason score;
• clinical stage;
• prostate MRI where appropriate;
• prostate-volume assessment;
• baseline urinary symptom scoring, often with IPSS;
• urinary flow assessment in selected patients;
• review of prior TURP or other prostate procedures; and
• staging imaging where indicated by risk group.

A CT scan is not routinely performed simply to make sure the pelvic bones do not block the needles, as the old page suggested. Imaging is used more broadly for treatment planning, staging and anatomy.

Why Does Baseline Urinary Function Matter?

Brachytherapy commonly causes temporary swelling and irritation of the prostate and urethra.

A man who already has severe:

• weak urinary stream;
• high residual urine;
• frequent retention;
• severe urgency/frequency; or
• very high IPSS

may have a greater risk of significant urinary problems after treatment.

This is why urinary function is one of the most important factors when selecting patients for brachytherapy.

Does Prostate Size Matter?

A very large prostate can make needle placement and radiation planning more difficult.

Large lateral lobes or pubic-arch interference may limit access to parts of the gland.

In selected patients, several months of ADT may be used before brachytherapy to reduce prostate size.

But there is no single universal prostate-volume cutoff that determines eligibility in every center.

Can You Have Brachytherapy After TURP?

A previous transurethral resection of the prostate (TURP) is not necessarily an absolute contraindication.

Current EAU guidance states that brachytherapy may be feasible after an appropriately performed TURP if sufficient prostate tissue remains and careful dose planning is used.

EAU recommends waiting at least approximately 3 months after TURP to allow healing.

However, individual urinary anatomy and incontinence risk still matter.

What Are the Main Benefits of Seed Implant Brachytherapy?

Potential advantages include:

• highly localized radiation dose;
• one implantation procedure rather than weeks of daily treatment for LDR monotherapy;
• outpatient or short-stay treatment in many centers;
• excellent cancer control in appropriately selected localized disease;
• low rates of severe bowel toxicity when performed well; and
• lower risk of urinary incontinence than radical prostatectomy for many men.

Is Seed Implantation “As Good as Surgery”?

This question does not have one universal answer.

Both surgery and brachytherapy can provide excellent long-term cancer control for appropriately selected localized prostate cancer.

But there is limited randomized evidence directly comparing radical prostatectomy with modern brachytherapy.

Choice therefore depends on:

• risk group;
• age and life expectancy;
• urinary function;
• sexual function;
• other medical conditions;
• patient preference; and
• local expertise.

It is more accurate to say that brachytherapy is an established curative radiation option for selected localized disease—not that it has been proven universally equal or superior to surgery.

What Are the Most Common Side Effects?

Urinary Frequency and Urgency

Urinary irritation is one of the most common short-term effects.

Men may notice:

• more frequent urination;
• urgency;
• night-time urination;
• burning;
• weaker stream; and
• difficulty starting urination.

Symptoms may worsen during the first weeks and can take several months to settle.

Urinary Retention

Temporary prostate swelling can occasionally make it impossible to empty the bladder.

Blood in the Urine

A small amount of blood in the urine is common for a short time after seed implantation.

Heavy bleeding, large clots, inability to urinate or worsening symptoms should be reported promptly.

Perineal Bruising or Tenderness

Because needles pass through the perineum, temporary:

• bruising;
• swelling;
• tenderness; and
• minor bleeding

are common immediately after treatment.

Bowel and Rectal Side Effects

The prostate lies directly in front of the rectum, so radiation can irritate rectal tissue.

Possible symptoms include:

• rectal discomfort;
• more frequent bowel movements;
• urgency;
• mucus;
• minor rectal bleeding; and
• rarely more serious late rectal injury.

Severe long-term gastrointestinal toxicity is uncommon with modern prostate brachytherapy.

Sexual Side Effects

Erectile dysfunction can develop gradually after brachytherapy.

The risk is influenced by:

• age;
• erectile function before treatment;
• diabetes and vascular disease;
• radiation dose;
• whether external-beam radiation is also used; and
• whether ADT is given.

Some men also notice reduced semen volume or eventually a dry orgasm.

Does Brachytherapy Cause Urinary Incontinence?

Severe urinary incontinence is generally uncommon after primary brachytherapy and tends to occur less often than after radical prostatectomy.

However, risk can be higher in men with previous prostate surgery such as TURP or substantial pre-treatment urinary dysfunction.

Urethral Stricture

Radiation can rarely cause scar tissue that narrows the urethra.

Symptoms can include:

• progressively weaker stream;
• straining;
• incomplete emptying; and
• recurrent urinary retention.

Some strictures require a urological procedure.

Are the Seeds Dangerous to Other People?

After LDR permanent seed implantation, very small amounts of radiation may temporarily be detectable outside the body.

The radiation travels only a short distance, so exposure to others is low.

However, the treatment team may advise temporary precautions such as:

• limiting prolonged close contact with pregnant people;
• limiting prolonged close contact with babies or very young children;
• following specific distance/time instructions for several weeks or months; and
• carrying treatment documentation when traveling because some radiation detectors can occasionally identify the implant.

Instructions vary according to isotope, dose and local radiation-safety policy, so follow the treating center’s guidance rather than generic internet rules.

Can a Seed Come Out?

Rarely, a seed can migrate from its original position or pass through the urinary tract.

Some centers advise patients to:

• strain urine temporarily;
• use a condom during intercourse for a specified period; and
• contact the radiation team if a seed is found.

Modern linked or stranded seed techniques can reduce migration risk.

Are Radiation Precautions Needed After HDR?

No.

HDR radioactive material is removed before treatment is complete.

Once the source has been removed, there is no radioactive material left in the patient and no radiation exposure risk to family members.

How Fast Can You Return to Normal Activity?

Recovery from the implantation procedure itself is usually fairly quick.

Many men return to light activities within a few days.

However, centers often advise avoiding:

• heavy lifting;
• vigorous exercise;
• bicycling; and
• other activities that put substantial pressure on the perineum

for a short period.

The exact timing should follow the treatment center’s instructions.

What Happens to PSA After Seed Implantation?

Unlike prostatectomy, brachytherapy leaves the prostate gland in place.

Therefore, PSA is not expected to become immediately undetectable.

PSA usually falls gradually over months or years.

EAU notes that after definitive radiation, reaching the lowest PSA level can take up to three years or more.

What Is a PSA Bounce?

A PSA bounce is a temporary rise in PSA followed by another decline.

It can occur after both external-beam radiation and brachytherapy, often within the first few years.

NCI specifically notes that PSA bounce does not automatically mean the cancer has returned.

How Is Recurrence Defined After Radiation?

For definitive radiation therapy, including brachytherapy-based treatment, the commonly used Phoenix definition of biochemical recurrence is:

PSA rise of more than 2 ng/mL above the lowest post-treatment PSA (nadir).

This differs from prostatectomy, where PSA is expected to fall to very low or undetectable levels because the prostate has been removed.

Does Brachytherapy Affect Fertility?

Yes.

Radiation to the prostate and reproductive tract can significantly reduce fertility, and semen volume may decline.

Men who may want biological children in the future should discuss sperm banking before treatment.

Can Prostate Cancer Seed Implantation Be Repeated?

It is not normally repeated routinely after successful primary treatment.

However, carefully selected men with biopsy-proven local recurrence after previous radiotherapy can sometimes undergo salvage LDR or HDR brachytherapy at experienced centers.

Salvage brachytherapy has greater potential for urinary and rectal toxicity and requires careful confirmation that the cancer is truly localized and that distant metastases are absent.

How Does Seed Implantation Compare With External-Beam Radiation?

For the complete radiation overview, see radiation therapy for prostate cancer.

Questions to Ask Before Choosing Seed Implantation

1. Am I low-, intermediate- or high-risk?
2. Would active surveillance be reasonable for me?
3. Should brachytherapy be used alone or as a boost with external-beam radiation?
4. Is LDR or HDR more appropriate?
5. How good is my baseline urinary function?
6. What is my IPSS and urinary flow rate?
7. Is my prostate size/anatomy suitable?
8. Will I need ADT?
9. How often does your center see urinary retention or urethral stricture?
10. What radiation precautions will I need?
11. How will PSA be monitored afterward?
12. What should I expect regarding erectile function and fertility?

Medical information notice: Prostate brachytherapy requires careful selection by an experienced radiation oncology team. Risk group, prostate anatomy, urinary function, previous prostate procedures and the need for external-beam radiation or ADT all influence whether seed implantation is appropriate.