01Purpose and principlesWhat the treatment does and how it fits into care.
Radiotherapy aims to maximise tumour-control probability while constraining normal-tissue complication. External-beam planning uses simulation images and reproducible immobilisation to define visible tumour, subclinical-risk volumes and setup margins. Organs at risk are contoured and dose-volume constraints applied. Image guidance verifies position during treatment. Brachytherapy places a source close to or within the target and has separate procedural safety.
Fractionation exploits differences in repair, repopulation, redistribution and reoxygenation. Hypofractionation gives fewer larger fractions in evidence-based settings; conventional fractionation uses smaller repeated doses; stereotactic treatment delivers highly conformal ablative doses to selected small targets. Concurrent chemotherapy or radiosensitisers can improve control but increase acute and late toxicity.
Toxicity follows field, dose, fraction size, previous treatment and patient factors. Skin reaction, mucositis, oesophagitis, diarrhoea, urinary symptoms and fatigue are common acute patterns. Late effects include fibrosis, strictures, organ dysfunction, endocrine failure, cognitive change, fracture and second malignancy. New severe symptoms still require assessment for infection, thrombosis or cancer progression rather than automatic attribution to radiation.
Key points
- Radiotherapy deposits ionising energy that damages DNA directly and through free radicals; fractionation allows normal-tissue repair while repeated exposure accumulates tumour effect.
- Treatment may be definitive, neoadjuvant, adjuvant, consolidative or palliative and can use external beam, stereotactic techniques or brachytherapy.
- CT simulation, immobilisation, target and organ-at-risk contouring, dose planning and independent checks precede the first fraction.
- Dose and fractionation are tumour-, site- and intent-specific; use the current Royal College of Radiologists guidance and local protocol rather than memorised schedules.
- Radiosensitivity, oxygenation, concurrent systemic treatment, previous irradiation and normal-tissue reserve affect both control and toxicity.
- Acute effects occur in proliferating tissues during or soon after treatment; late fibrosis, vascular, neurological, endocrine and second-cancer effects can appear months or years later.
- Palliative radiotherapy can rapidly relieve bone pain, bleeding, obstruction or neurological risk, but emergency corticosteroid, surgery or stabilisation may also be needed.
- Pregnancy, implanted devices, transport burden and inability to reproduce position require early planning, not day-one improvisation.
02Indications, selection and cautionsWho may benefit, who needs urgent treatment and important alternatives.
Definitive or perioperative radiation is selected when local control contributes meaningfully to cure or durable disease control.
Painful bone metastasis, bleeding, compression or symptomatic local mass may improve with a shorter burden-sensitive course.
Erythema, mucositis, odynophagia, diarrhoea or cystitis appears in irradiated tissues during treatment and shortly afterwards.
Fibrosis, vascular change, endocrine loss, neuropathy, fracture or organ dysfunction can develop long after the acute reaction resolves.
Cord compression, airway compromise or cerebral oedema requires urgent multidisciplinary rescue; radiotherapy planning must not delay immediate stabilisation.
03Assessment before treatmentTests and checks that guide safe selection.
Read from the initial assessment onwards. Tests may run in parallel in urgent care; first-line, preferred, confirmatory, definitive and gold-standard labels appear only when the chapter explicitly states them.
- 01
Planning CT with immobilisationFirst step - Why
- Create the reproducible geometry used for target and organ contouring.
- Interpretation and limitations
- Position, bladder or bowel preparation and contrast must match treatment needs; movement or anatomy change can invalidate the plan.
- 02
MRI or PET image fusion - Why
- Improve target definition where soft tissue or biological information changes contouring.
- Interpretation and limitations
- Registration error and treatment-position differences matter; fused images supplement rather than replace planning geometry.
- 03
Dose-volume plan review - Why
- Verify target coverage and normal-tissue constraints before treatment.
- Interpretation and limitations
- The radiation oncologist and physics team assess hotspots, organ doses, previous irradiation and technical deliverability through independent checks.
- 04
On-treatment imaging - Why
- Confirm anatomy and positioning during the course.
- Interpretation and limitations
- Image guidance detects setup error and anatomical change; major weight loss, tumour shrinkage or organ filling may require replanning.
- 05
Toxicity and blood monitoring - Why
- Detect field- and combination-specific adverse effects.
- Interpretation and limitations
- Assess skin, mucosa, intake, bowel, bladder, marrow and organ function according to site and concurrent systemic treatment.
04Treatment approachPreparation, options, escalation and aftercare.
01PlanDefine intent and geometryFirst stepRadiotherapy is proposed after diagnosis and staging.+
- 1Agree curative or palliative intent, alternatives and the evidence-based dose-fractionation option at MDT and consultation.
- 2Complete simulation, immobilisation and image fusion, then contour targets and organs at risk using tumour-specific standards.
- 3Perform physics optimisation and independent verification, including previous-dose review and pregnancy or device precautions before first exposure.
02DeliverMaintain safe reproducibilityThe approved plan enters treatment within the planned cancer pathway.+
- 1Verify identity, site, consent, setup and image guidance at each attendance, following correction thresholds before beam delivery.
- 2Review acute toxicity, nutrition, analgesia and concurrent medicines during the course, interrupting only when benefit-risk and recovery require it.
- 3Replan when anatomy changes materially rather than continuing a geometrically invalid treatment for convenience.
03FollowManage response and late effectsThe course completes or palliative benefit is being assessed.+
- 1Provide expected timing of acute peak and recovery, field-specific self-care and emergency symptoms such as dehydration or neurological decline.
- 2Assess response at the tumour-appropriate interval because early imaging can reflect inflammation rather than final control.
- 3Monitor late organ effects and rehabilitation needs, preserving prior field and dose information for future procedures or re-irradiation decisions.
05Complications, monitoring and follow-upAdverse effects, response and longer-term review.
- Review setup images and delivery records throughout treatment, investigating repeated shifts rather than normalising them.
- Assess field-specific skin, mucosal, gastrointestinal, urinary, neurological and marrow effects at planned on-treatment reviews.
- Track weight, hydration, pain and nutrition, arranging dietetic or feeding support before severe depletion interrupts curative therapy.
- Document cumulative dose, fractionation, technique, field and organs at risk for lifelong access and any future re-irradiation.
- At follow-up separate expected treatment evolution from recurrence and screen for site-specific late endocrine, vascular, skeletal and functional effects.
06Special situationsVariants, exceptions and circumstances that change the usual approach.
Fraction is biological
The same total physical dose given in different fraction sizes can have different tumour and late-tissue effects.
Geometry is treatment
A technically perfect dose plan fails if the person cannot reproduce position or internal organs move outside the planned relationship.
Acute and late differ
Severe early mucosal reaction does not translate directly into every late effect, although field and combined treatment influence both.
Palliation can be short
Evidence-based shorter schedules reduce travel and treatment burden without implying that symptom relief is less active care.
Prior dose follows patients
Previous fields and organ doses constrain future surgery and radiotherapy even many years later.
07Common pitfallsFrequent interpretation and management errors.
- 01
Using one fractionation schedule for every tumour.
- 02
Treating planning CT as a diagnostic scan only.
- 03
Ignoring weight or anatomy change during treatment.
- 04
Attributing every new symptom to radiation.
- 05
Losing prior field and dose records.
- 06
Delaying emergency stabilisation for routine planning.