Brachytherapy — How It Works, Benefits & Recovery — Procedure Guide, Recovery & Risks | MyMedicPlus

Brachytherapy is a form of internal radiation therapy in which radioactive sources are placed directly inside or immediately adjacent to a tumour, delivering highly concentrated radiation doses from within the body rather than from an external beam. The word derives from the Greek 'brachy' meaning short distance, reflecting the centimetre-scale proximity of the radiation source to the target tissue. Two principal modalities exist: high-dose rate (HDR) brachytherapy, which uses a single high-activity iridium-192 source temporarily introduced into applicator catheters or needles for treatment sessions of 10–30 minutes each, and low-dose rate (LDR) brachytherapy, which uses permanently implanted radioactive seeds — typically iodine-125 or palladium-103 for prostate cancer — that emit radiation slowly over weeks to months as they decay. A third modality, pulsed-dose rate (PDR) brachytherapy, delivers intermittent pulses approximating LDR biology in specialist gynaecological cancer centres. The physics principle underlying brachytherapy is the inverse square law: radiation intensity falls off with the square of distance, so doubling the distance reduces the dose to one quarter. This steep dose gradient is clinically exploited to deliver very high tumour doses while the bowel, bladder, rectum, and other critical structures centimetres away receive dramatically lower radiation. Brachytherapy can be used as a definitive primary treatment, as a boost to external beam radiotherapy, or as salvage treatment after external radiation.

Brachytherapy is indicated across several cancer types where the tumour anatomy allows close source placement. Prostate cancer: LDR permanent seed implant is a definitive curative treatment for low- and favourable-intermediate-risk localised prostate cancer; HDR brachytherapy is used as a boost after external beam radiotherapy for higher-risk disease, delivering a single high-dose fraction directly to the gland. Cervical cancer: HDR brachytherapy with intracavitary applicators (tandem and ring or ovoid) placed in the uterine cavity and vaginal fornices is the standard of care following external pelvic radiotherapy and concurrent cisplatin chemotherapy, critical to achieving local control rates above 85% for locally advanced disease. Endometrial and vaginal cancer: vaginal vault brachytherapy using a cylinder applicator reduces local recurrence after hysterectomy. Breast cancer: partial breast irradiation via implanted catheters or SAVI applicator delivers accelerated treatment over 5 days as an alternative to whole-breast radiotherapy in selected low-risk patients. Head and neck, skin, and bile duct brachytherapy complete the range of clinical applications. Patient selection considers tumour size, location, proximity to critical structures, and prior treatments.

The specific technique varies by tumour site. For prostate LDR seed implant, the patient is positioned in dorsal lithotomy under spinal or general anaesthesia. Transrectal ultrasound guidance is used to image the prostate in real time as hollow needles are inserted transperineally through a template grid. Between 80 and 120 titanium seed capsules, each 4.5 mm long and containing radioactive iodine-125, are deposited via the needles throughout the prostate volume using a pre-planned seed distribution calculated to achieve a prescribed dose of 145 Gy (iodine-125) to 90% of the prostate. For HDR brachytherapy of the cervix, an intracavitary applicator set (tandem inserted through the cervical os into the uterine cavity and ring or ovoids positioned in the vaginal fornices) is placed under general or spinal anaesthesia and secured with vaginal gauze packing. CT or MRI images are acquired with the applicator in situ. A radiation oncologist and physicist contour the high-risk clinical target volume and organs at risk, calculate a treatment plan, and the iridium-192 source is driven remotely through the applicator in a sequence of dwell positions and times to achieve the planned dose distribution. Applicators are removed after each fraction. Treatment is delivered over 2–5 fractions on sequential or alternate days.

The defining clinical benefit of brachytherapy is the ability to deliver biological radiation doses to the tumour that would be impossible with external beam techniques alone, because the dose gradient protects surrounding normal tissue. For low-risk prostate cancer, LDR brachytherapy achieves 10-year biochemical control rates of 85–92% in a single outpatient procedure without the 7–8 weeks of daily hospital visits required by conventional external beam radiotherapy. The same-day or next-day discharge with rapid return to normal activities is a major quality-of-life advantage over surgical alternatives. For cervical cancer, the addition of HDR brachytherapy to chemoradiotherapy increases the probability of local tumour control by 15–20 percentage points compared with external beam radiotherapy alone and reduces radiation doses to the rectum and bladder by exploiting the brachytherapy dose gradient. Survival rates for locally advanced cervical cancer treated with modern image-guided adaptive brachytherapy (IGABT) have improved to 65–75% at 5 years in major European studies (EMBRACE study). Partial breast brachytherapy condenses a 6-week radiotherapy course into 5 days with equivalent local control at 5 years, offering significant convenience and equivalent cosmetic outcomes in selected patients.

Side effects of brachytherapy depend on the treated site and the technique used. Prostate LDR implant: urinary frequency, urgency, and obstructive symptoms occur in 50–70% of patients in the first 3–6 months due to prostatic oedema from the needle insertion; these resolve as the radioactivity decays. Urinary retention requiring catheterisation occurs in 5–15% and is more common in men with pre-existing benign prostatic hypertrophy. Erectile dysfunction develops gradually over 2–5 years in 30–50%. Rectal irritation and bleeding are less common than with external beam radiotherapy due to the sharp dose gradient. Cervical HDR brachytherapy causes acute vaginal mucositis, pelvic discomfort, and Eustachian tube-like pressure during applicator placement. Late effects include vaginal stenosis (requiring regular use of a vaginal dilator), bladder haemorrhage, and rectal fistula (less than 2% with image-guided planning). Seed migration from the prostate to the lung has been reported in LDR implant but is clinically insignificant. All brachytherapy patients require radiation protection advice relevant to the specific modality used.

HDR brachytherapy recovery is rapid: most patients are discharged on the day of or the day after each fraction with mild analgesics. For cervical cancer patients, cumulative fatigue from concurrent chemotherapy and external radiotherapy is the dominant challenge. Prostate LDR seed implant requires a brief hospital stay of up to 24 hours. Patients are advised to use a urine strainer for the first 2 weeks to capture any seeds that may pass into the urine (rare but possible). Radiation precautions for prostate seed patients include avoiding close prolonged contact with pregnant women and children under 10 for 2 months; sitting more than 15 cm from others poses no risk. Activity can be resumed within 3–5 days, with avoidance of strenuous exercise for 2 weeks. Alpha-blocker medication is usually prescribed for 3–6 months to ease urinary symptoms. Follow-up PSA measurements at 3, 6, and 12 months, then annually, monitor oncological response. Cervical cancer patients receive vaginal dilators and lubricants to prevent stenosis and are followed with gynaecological examination and pelvic MRI at 3 months.