Radiation Therapy — Procedure Guide, Recovery & Risks | MyMedicPlus

Radiation therapy (radiotherapy) is a cornerstone treatment modality in oncology that uses high-energy ionising radiation to damage the DNA of cancer cells, impairing their capacity to replicate and triggering cell death through apoptosis and mitotic catastrophe. Unlike systemic therapies that circulate throughout the body, radiation therapy is a localised treatment -- precisely directed at the tumour volume while minimising dose to surrounding healthy tissues, a principle described as the therapeutic ratio.

The principal delivery modalities are external beam radiotherapy (EBRT) and brachytherapy. EBRT uses a linear accelerator (LINAC) to generate high-energy photon (X-ray) beams in the 6-18 MV range, directed at the patient from outside the body via a rotating gantry. Advanced EBRT techniques include intensity-modulated radiotherapy (IMRT), which modulates beam intensity across multiple fixed angles to sculpt dose around critical structures; volumetric modulated arc therapy (VMAT), which delivers IMRT continuously as the gantry rotates; and stereotactic body radiotherapy (SBRT), which delivers ablative doses in 1-5 fractions with extreme precision for small tumours. Stereotactic radiosurgery (SRS) -- delivered via Gamma Knife, CyberKnife, or LINAC-based systems -- provides intracranial single-fraction ablative treatment for brain metastases, arteriovenous malformations, and trigeminal neuralgia.

Brachytherapy delivers radiation internally by placing radioactive sources directly within or immediately adjacent to the tumour. High-dose rate (HDR) brachytherapy uses iridium-192 afterloaded remotely via applicators placed in the cervix, prostate, or bronchus. Low-dose rate (LDR) brachytherapy permanently implants iodine-125 or palladium-103 seeds in the prostate. Brachytherapy achieves biologically effective doses substantially higher than EBRT alone, improving local control for cervical and prostate cancer.

Radiation therapy is used across more than 50% of all cancer diagnoses -- both for curative-intent treatment and for palliation of symptoms -- making it one of the most widely used cancer treatments globally alongside surgery and systemic therapy.

Radiation therapy is indicated across a broad spectrum of malignant and selected benign conditions, used with curative intent, as adjuvant or neo-adjuvant therapy, in combination with systemic treatment, or for palliation of symptoms.

Curative-intent radiotherapy: - Head and neck cancers: Definitive concurrent chemoradiotherapy with cisplatin achieves cure in the majority of patients with stage III-IV squamous cell carcinoma of the oropharynx, hypopharynx, and larynx, preserving organ function. HPV-positive oropharyngeal cancer has a particularly favourable prognosis with chemoradiation. - Prostate cancer: EBRT or HDR brachytherapy achieves 10-year biochemical control of 85-90% for low-risk and 70-80% for intermediate-risk localised prostate cancer. - Cervical cancer: Concurrent cisplatin chemoradiotherapy with HDR brachytherapy boost achieves 5-year survival of 65-80% for locally advanced disease. - Early-stage lung cancer (SBRT): 3-5-fraction SBRT achieves 3-year local control of 85-95% in medically inoperable stage I non-small cell lung cancer. - Hodgkin lymphoma: Involved-site radiotherapy (ISRT) following chemotherapy provides excellent long-term disease control with reduced late toxicity compared with older extended-field techniques.

Adjuvant radiotherapy (after surgery): - Breast cancer: Whole-breast or partial-breast radiotherapy after lumpectomy reduces 10-year ipsilateral recurrence from approximately 25% to under 7%. - Rectal cancer: Post-operative pelvic radiotherapy reduces local recurrence risk for high-risk stage II-III disease with close margins or nodal involvement. - High-grade glioma (glioblastoma): Temozolomide concurrent chemoradiotherapy to 60 Gy (Stupp protocol) after debulking surgery is the standard of care. - Soft tissue sarcoma: Adjuvant radiotherapy significantly reduces local recurrence risk after limb-sparing surgery for high-grade, large (over 5 cm) tumours.

Neo-adjuvant radiotherapy (before surgery): Long-course chemoradiotherapy for rectal cancer achieves pathological complete response in 15-25% of patients and significantly improves oncological outcomes. Short-course radiotherapy (5 Gy x 5 fractions) is an effective alternative for resectable rectal cancer with equivalent long-term results.

Palliative radiotherapy: Short-course palliative radiotherapy (1-10 fractions) provides meaningful symptom relief for: bone metastases (pain control in 60-80% of patients, with a single 8 Gy fraction as effective as multi-fraction schedules for uncomplicated disease); spinal cord compression (prevents or reverses neurological deterioration); brain metastases (stereotactic radiosurgery for 1-4 lesions, whole-brain for multiple metastases); and obstruction of the airway, oesophagus, or superior vena cava.

Benign conditions: Targeted low-dose radiotherapy treats: keloid scars after excision (reducing recurrence from 50-80% to under 20%); heterotopic ossification after hip replacement; and -- via stereotactic radiosurgery -- arteriovenous malformations and trigeminal neuralgia refractory to medication.

Contraindications: Absolute contraindications include pregnancy (particularly first trimester with abdominal fields), prior radiation at or near tolerance doses to the same field, and active connective tissue disease (systemic lupus erythematosus with pulmonary involvement). Pacemakers and cochlear implants in the treatment field require specialist dosimetric assessment before proceeding.

Treatment planning begins with CT simulation and tumour volume delineation. IMRT delivers dose from multiple angles with intensity modulation to sculpt dose around critical structures. VMAT delivers continuous arc therapy in a single rotation. SBRT delivers large doses in 1–5 fractions. Brachytherapy places sealed radioactive sources (iridium-192 for HDR, iodine-125 for LDR) within or adjacent to the tumour. Treatment planning begins with CT simulation and tumour volume delineation. IMRT delivers dose from multiple angles with intensity modulation to sculpt dose around critical structures. VMAT delivers continuous arc therapy in a single rotation. SBRT delivers large doses in 1–5 fractions. Brachytherapy places radioactive sources directly within or adjacent to the tumour via catheters, seeds, or applicators. Proton therapy uses proton beams with a Bragg peak to deposit dose at precise depth with minimal exit dose. Image-guided radiotherapy (IGRT) uses daily cone-beam CT or X-ray imaging to align the patient to the planned target volume, correcting for inter-fraction positioning variation. Adaptive radiotherapy re-plans treatment mid-course to account for tumour regression or patient anatomical changes. Each external beam fraction takes 10–20 minutes on the linear accelerator; treatment courses range from a single fraction (for pain palliation) to 33–35 daily fractions over 7 weeks for definitive curative treatment.

Acute side effects (fatigue, skin erythema, mucositis, dysphagia depending on site) peak at week 3–4 and resolve within 2–6 weeks of treatment completion. Patients are reviewed weekly during treatment. Late effects (fibrosis, lymphoedema, hormonal changes) may emerge months to years later and require long-term follow-up. Acute side effects (fatigue, skin erythema, mucositis, dysphagia depending on site) peak at week 3–4 and resolve within 2–6 weeks of treatment completion. Patients are reviewed weekly during treatment. Late effects (fibrosis, lymphoedema, hormonal changes) may emerge months to years later and require long-term surveillance and specialist management. Salivary gland dysfunction after head and neck radiotherapy is managed with saliva substitutes, pilocarpine, and dental fluoride prophylaxis. Pelvic radiotherapy late effects (bowel and bladder dysfunction) are managed by gastroenterology and urology teams using evidence-based algorithms.

Acute side effects vary by site: mucositis and xerostomia (head and neck), radiation pneumonitis (lung), enteritis (abdomen/pelvis), and cystitis (prostate). Late effects include fibrosis, secondary malignancy (0.5–1% lifetime risk), neurocognitive changes (brain), lymphoedema, and bowel dysfunction. IMRT significantly reduces late toxicity versus conventional radiotherapy. Acute side effects vary by site: mucositis and xerostomia (head and neck), radiation pneumonitis (lung), enteritis (abdomen/pelvis), and cystitis (prostate). Late effects include fibrosis, secondary malignancy (0.5–1% lifetime risk), neurocognitive changes (brain), lymphoedema, and bowel dysfunction. Modern IMRT and proton therapy significantly reduce late toxicity by sparing organs at risk. Radiation recall — skin reaction in previously irradiated fields triggered by chemotherapy (doxorubicin, gemcitabine) — is managed by drug dose modification. Prostate radiotherapy late effects include erectile dysfunction and urinary incontinence in a minority of patients; these are managed similarly to post-surgical deficits.

Curative radiotherapy achieves 5-year local control of 80–90% for early-stage prostate cancer, 85–95% for early laryngeal cancer, and 60–80% for localised non-small cell lung cancer treated with SBRT. Palliative radiotherapy provides meaningful pain relief in 60–80% of patients with bone metastases within 4 weeks. Curative radiotherapy achieves 5-year local control of 80–90% for early-stage prostate cancer, 85–95% for early laryngeal cancer, and 60–80% for localised non-small cell lung cancer treated with SBRT. Palliative radiotherapy provides meaningful pain relief in 60–80% of patients with bone metastases within 2 weeks. Concurrent chemoradiotherapy with cisplatin or carboplatin improves survival for head and neck, cervical, oesophageal, and lung cancers by 10–15% absolute at 5 years compared to radiotherapy alone. Definitive radiotherapy for anal canal cancer (combined with mitomycin-C and 5-fluorouracil) achieves colostomy-free survival in 65–75%, preserving bowel function without surgery.