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Breast cancer — radiotherapy
Breast-conserving surgery almost always requires breast radiation; after mastectomy you irradiate when the risk of locoregional relapse is high; and every plan keeps the heart dose as low as possible.
Why it matters in the exam
The radiation part of the bank asks a lot about the breast: who can skip radiation, who suits partial breast irradiation (APBI), when chest wall radiation after mastectomy is needed, what the boost added in the EORTC trial, what the MA.20 trial found for nodal radiation, and what is known about cardiac toxicity. The stem gives age, tumour size, margins, nodes and receptors, and the answer depends on the risk factors for local relapse.
The exam also asks about the axilla — when dissection can be skipped and when radiation replaces it.
Key points
- Breast conservation = surgery plus radiation; hypofractionation is standard today.
- The boost reduces local relapse, mainly in young women, with no survival benefit.
- Older low-risk patients on endocrine therapy may omit radiation.
- PMRT is given for 4 or more nodes, T4 or positive margins; 1 to 3 nodes — individual.
- Cardiac toxicity depends on dose with no safe threshold; DIBH reduces it.
Summary table
| Situation | Recommendation | Exam detail |
|---|---|---|
| After breast-conserving surgery | Whole-breast radiation, usually hypofractionated | 40 Gy in 15 fractions or 26 Gy in 5 fractions |
| Boost to the tumour bed | Mainly young age, high grade or close margins | Reduces local relapse; largest absolute benefit at age 40 and below; no survival gain |
| Omitting radiation | Age 65 or more, T1N0, HR-positive, clear margins, endocrine therapy | Slightly more local relapse, no loss of survival |
| Partial breast irradiation (APBI) | Age 50 or more, tumour up to 2 cm, clear margins, node-negative, ER-positive | Alternative to whole-breast radiation in low risk |
| After mastectomy (PMRT) | 4 or more nodes, T3 with nodes, T4 or positive margins | 1 to 3 nodes — individual decision; regional nodal radiation per MA.20 improves disease-free survival |
| Axilla with 1 to 2 positive sentinel nodes | After breast conservation and whole-breast radiation — axillary dissection can be omitted (Z0011) | Axillary radiation is an alternative to dissection with less lymphoedema (AMAROS) |
| Contraindications to breast conservation | Pregnancy needing radiation during it, prior chest radiation, diffuse malignant calcifications, repeatedly positive margins | Relative: active connective tissue disease such as scleroderma, and a large tumour-to-breast ratio |
In the full version for subscribers
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Sources
- NCCN Clinical Practice Guidelines in Oncology: Breast Cancer, 2026 — Principles of radiation therapy
- ASTRO Clinical Practice Guideline: Partial breast irradiation, 2023 — Patient selection
- Gunderson and Tepper's Clinical Radiation Oncology, 5th ed. (2021) — Early-stage breast cancer
Sources are given for further reading; the text is written afresh and not copied from them.
Reviewed by the Examqo AI Professor · 2026-11-06. The text may contain errors; when in doubt, check the source.