Prostate Ablation and Brachytherapy

Beyond surgery and external-beam radiation, localized prostate cancer can be treated by energy ablation (whole-gland or focal) and by brachytherapy (implanted radioactive seeds). Ablation destroys tumour with cold, heat, or electrical energy while sparing surrounding tissue; brachytherapy delivers a high radiation dose to the gland from within. Focal ablation rests on the index-lesion hypothesis (the largest, highest-grade focus drives tumour behaviour) — around 20% of cancers are unifocal — and aims to control disease with less morbidity than radical treatment. Patient selection, risk stratification, and radiation concepts are covered in the Prostate Cancer topic; whole-gland surgery on the Radical Prostatectomy page; this page is the procedural reference.

Patient Selection and Disease Localization

• Focal therapy is offered per AUA to selected, informed intermediate-risk patients (trial enrolment prioritised) — not routinely for low-risk (active surveillance) or high-risk (insufficient data) disease. The target lesion must be visible on mpMRI, concordant with histology, and clinically significant (generally Gleason 3+4 or higher and volume > 0.2 mL).
• Accurate localization is mandatory: an mpMRI plus a transperineal template mapping biopsy (3D template-mapping, e.g. the 20-zone modified Barzell scheme, up to ~90 cores at 5-mm sampling) is the restaging protocol before focal treatment — see the Prostate Biopsy page.
• Whole-gland cryoablation suits clinical stage T1c–T3 without metastasis, of any grade or hormonal status, in men with a 5–10-year life expectancy (including those unfit for surgery/radiotherapy); a gland > 50 mL may be downsized with neoadjuvant hormones. Absolute contraindications: a urethrorectal fistula, extensive periurethral cancer, or distorted pelvic anatomy. Salvage cryoablation after radiation failure needs biopsy-proven local recurrence and a negative metastatic workup — a PSA > 10 ng/mL or a doubling time under 6 months suggests metastasis and contraindicates salvage.
• Brachytherapy is risk-stratified: low-risk → seeds alone (no ADT); intermediate-risk → 6 months of ADT (or seeds + EBRT); high-risk → trimodal seeds + EBRT + ADT (T3 disease is not a candidate for seeds alone). A gland > 60 cc is hard to image/implant and can be reduced ~30% with 3 months of neoadjuvant ADT.

Ablative Modalities at a Glance

Modality	Mechanism	Energy / agent	Status
Cryotherapy	Freezing → coagulative necrosis + microvascular injury	Argon cool / helium thaw	Established
HIFU	Focused ultrasound heat (80–100°C) + cavitation	Ultrasound 0.8–4 MHz	Established
RFA	Resistive heat (~100°C) → coagulative necrosis	RF 450–1200 kHz, ≤ 100 W	Emerging
Photodynamic (vaPDT)	Light-activated drug → singlet oxygen	Photosensitiser + laser light	Experimental
Irreversible electroporation	Non-thermal membrane nanopores	Electrical pulses (NanoKnife)	Experimental
Focal laser ablation	Laser thermal coagulation	Diode laser 6–25 W	Experimental

Cryotherapy

Mechanism

Very low sub-zero temperatures cause coagulative necrosis through two mechanisms: direct ice-crystal formation with dehydration and membrane disruption, and microvascular injury producing ischaemic necrosis beyond the visible iceball. Modern systems use argon to cool and helium to thaw (Joule-Thomson effect) through 17-gauge percutaneous probes. Crucially, the iceball seen on ultrasound (the 0°C edge) is larger than the cytocidal zone — the lethal −40°C isotherm is smaller, so probe spacing must account for it.

Technique

• Dorsal or extended lithotomy; a biplanar transrectal ultrasound probe with a brachytherapy template guides transperineal probe placement, and a urethral warmer circulates fluid at 40–43°C to protect the urethra/sphincter.
• Probes: either 5–6 larger V-Probes (2.4 mm) or 12–15 fine 17-gauge CryoNeedles. Place them within 1 cm of the capsule, more than 0.5 cm from the rectum and urethra, and less than 2 cm apart (a "stick" freeze anchors the first probe). Position thermosensors at Denonvilliers' fascia, a neurovascular bundle, and the prostate.
• Freeze: activate the anterior probes first (their iceball "blacks out" the view), aiming for a minimum intraprostatic −40°C with the iceball carried 2–4 mm into periprostatic tissue but not into the rectal wall. Two freeze-thaw cycles are used (freeze ~8 min for V-Probes, ~10 min for CryoNeedles), with passive (gradual) thawing to maximise cell kill; a pull-back treats a gland longer than 3.5 cm. Remove the probes only after thawing past 5°C — pulling a still-frozen probe fractures the gland and bleeds.
• Focal cryoablation aims for −40°C anteriorly and 0°C at Denonvilliers' fascia and the external sphincter, with the urethral warmer removed ~2 hours postoperatively.

Postoperative Care and Complications

A suprapubic or urethral catheter stays 1–2 weeks; PSA is checked at 3 and 6 months. Focal-cryotherapy complications include LUTS (~1 in 3), erectile dysfunction (1–2 in 10), pad-requiring incontinence (~1 in 20–40), infection (~5%), and rare bowel injury or fistula.

High-Intensity Focused Ultrasound (HIFU)

Mechanism

A transducer focuses ultrasound (0.8–4 MHz, ~10,000× the energy of diagnostic ultrasound) to a point where the temperature reaches 80–100°C in seconds, causing coagulative necrosis by heat and by cavitation (microbubble formation and collapse); tissue outside the focus is spared.

Technique

• Extended lithotomy (Sonablate) or right lateral decubitus (Ablatherm), with an endorectal treatment probe and rectal cooling. Nitrous oxide is avoided (it causes prostatic microbubbles that disrupt targeting). For whole-gland therapy, a mini-TURP 4–6 weeks before (or a suprapubic catheter) reduces stricture risk.
• The Sonablate (treats prostates ≤ 40 mL, lesions 10–12 mm) allows operator-adjusted power; the Ablatherm (predefined power, lesions 19–26 mm) adds automated rectal-wall monitoring. The urethral catheter stays 5–10 days.

Postoperative Care and Complications

Discharge is usually same-day; alpha-blockers for up to 14 days. Retrograde ejaculation/anejaculation is common (~50%), UTI and epididymo-orchitis each 5–10%, pad-requiring incontinence 1–2%, and acute retention 1–2%; the most serious complication is a rectourethral fistula (~1 in 500), and about 1 in 5 men need a second treatment.

Emerging Ablative Modalities

• Radiofrequency ablation — resistive heating to ~100°C via monopolar or bipolar electrodes (a generator up to 100 W at 450–1200 kHz); RF conducts poorly through fat, giving the rectal wall and neurovascular bundles natural protection. Used for localized or hormone-resistant recurrence; complications (< 5%) are self-limiting bleeding, infection, and pain, with rectourethral fistula < 1%.
• Vascular-targeted photodynamic therapy (vaPDT) — an intravenous photosensitiser (e.g. WST-11) activated by laser light in the presence of oxygen generates cytotoxic singlet oxygen; vascular agents activate within minutes and clear rapidly (little skin/retinal accumulation). Used in trials for radiorecurrent and focal disease; the characteristic risk is a photosensitivity "sunburn" reaction, with rare rectourethral fistula.
• Irreversible electroporation (IRE, NanoKnife) — non-thermal cell death by membrane nanopores, sparing vessels, nerves, and collagen. Delivered as ~90 pulses (70–90 ms) generating 20–40 A (< 20 A risks undertreatment, > 40 A risks thermal injury); needles are placed no more than 2 cm apart (3–4 needles, so tumours > 3 mL are difficult) with a 5 mm margin from the urethra and apex, under full muscle paralysis (cardiac synchronisation is not needed for the prostate).
• Focal laser ablation (FLA) — laser thermal coagulative necrosis, notable for MR compatibility (real-time MR thermometry). Diode-laser energy is delivered for 60–120 seconds at 6–25 W; suited to low-to-intermediate-risk disease (PSA < 15 ng/mL, Gleason 6–7, < T3a), with tumours > 2 cc difficult to treat in one application.

Brachytherapy

Permanent prostate brachytherapy (PPB) implants radioactive seeds transperineally under TRUS guidance for durable cancer control with low morbidity.

Isotopes

• Iodine-125 — half-life 60 days, average energy 0.028 MeV; prescription 144–160 Gy monotherapy. Its longer half-life suits well-to-moderately differentiated tumours (87.5% of decay in the first 6 months).
• Palladium-103 — half-life 17 days, higher dose rate; chosen for Gleason 7 or higher (≥ 124 Gy monotherapy, 100 Gy with EBRT, 115 Gy salvage).
• Cesium-131 — half-life 9.7 days. No isotope has proven superior.

Technique

Extended dorsal lithotomy with a TRUS probe and template. Following the Paterson-Parker principle (homogeneous dose from inhomogeneous source distribution), ~75% of activity is placed peripherally, with seeds delivered by a Mick applicator, preloaded needles, or strands under real-time planning. Peripheral needles go in first (they shift and distort the gland, so the plan is recaptured), then 5–7 interior needles. Dosing targets (I-125): D90 180–190 Gy, urethral UD30 < 150% of prescription, rectal V100 < 1.3 mL. Seminal vesicles are implanted for T3 disease (~100 Gy Pd-103). A final fluoroscopy and cystogram check for seeds in the bladder (1–5%, removed if present).

Postoperative Care and Complications

• CT post-implant dosimetry within 30 days (optimal 16 ± 4 days for Pd-103, 30 ± 7 days for I-125); the gland ultimately shrinks 40–50%.
• Acute urinary retention from prostatic oedema is managed with catheterisation/CIC, alpha-blockers, and NSAIDs; a post-implant TURP is deferred until 3–4 half-lives pass (Pd-103 ~51 days, I-125 ~180 days) because of a high late-incontinence risk (prolonged CIC is preferred).
• Radiation urethritis (irritative symptoms; earlier and briefer with Pd-103) and occasional proctitis (steroid suppositories). Radiation safety: use a condom for the first few ejaculations (a seed may be ejected) and avoid close contact with pregnant women and small children for at least one isotope half-life.