Brachytherapy — Internal Radiation Therapy

Brachytherapy, sometimes referred to as sealed-source radiotherapy, involves inserting radioactive isotopes enclosed within protective capsules, wires, seeds, or ribbons directly into or near malignant tissue. The treatment is categorised by its placement technique: interstitial brachytherapy places sources directly into tissues, such as the prostate gland, whereas intracavitary brachytherapy places them within naturally occurring body cavities, such as the cervix or uterine cavity. It may also be applied onto surface tissues via specialised moulds or plaques.

Techniques are further defined by the dose rate administered. Low-dose-rate (LDR) brachytherapy delivers continuous, gentle radiation over several days or permanently via implanted seeds. In contrast, high-dose-rate (HDR) brachytherapy delivers concentrated doses through temporary applicators over a series of brief outpatient sessions lasting only a few minutes each. Both modalities allow radiation oncologists to escalate the tumour dose safely beyond standard external beam radiotherapy limitations.

Brachytherapy plays a pivotal role in cancer management because it provides an effective balance between eradicating malignant tissue and preserving vital organ function. For cancers located near sensitive structures, such as the bladder, bowel, or rectum, delivering external radiation alone can sometimes lead to undesirable long-term side effects. Brachytherapy permits a higher curative radiation dose to be delivered directly to the target volume. Patients often experience shorter overall treatment schedules, faster recovery periods, and a lower risk of chronic complications, thereby maintaining their quality of life during and after treatment.

Before brachytherapy, detailed imaging is essential to delineate the exact tumour dimensions and surrounding anatomy. Magnetic resonance imaging (MRI), computed tomography (CT), and transrectal ultrasound (TRUS) are routinely employed for precise computerised treatment planning. Pathological grading, such as the Gleason score in prostate cancer, and clinical staging assessments determine patient eligibility. Whilst brachytherapy is not a biomarker itself, tumours undergo routine histological confirmation and molecular profiling to confirm they are suitable candidates for localised radiation therapy.

Brachytherapy is most frequently used in the management of prostate cancer, cervical cancer, and uterine (endometrial) cancer. It is also an established treatment modality for early-stage breast cancer following lumpectomy, head and neck malignancies, soft tissue sarcomas, vaginal cancer, and certain eye tumours like choroidal melanoma. In cervical cancer, brachytherapy is widely regarded as a fundamental component of curative treatment alongside chemoradiotherapy.

Brachytherapy is used either as a standalone curative treatment or in combination with external beam radiation therapy, chemotherapy, or surgery. In prostate cancer, it can be applied as monotherapy for low-risk disease or as a 'boost' combined with external beam radiation and hormone therapy for intermediate- or high-risk disease. For gynaecological malignancies, it typically follows concurrent chemoradiation. Side effects are largely localised and temporary, commonly involving urinary frequency, bowel irritation, or pelvic soreness.