External-beam partial breast irradiation treats the tumor bed region instead of the whole breast. Plans are small and conformal, and the main measure of a good plan is how well it spares the rest of the breast, the lung and the heart.
Partial breast irradiation treats only the region around the tumor bed rather than the whole breast. Randomized trials such as IMPORT LOW support it for selected lower-risk patients; who is suitable is set out in the ASTRO 2023 guideline.
Common schedules include 40.05 Gy in 15 fractions, 30 Gy in 5 fractions on alternate days and 26 Gy in 5 fractions.
What changes for the planner:
As for whole breast, with extra attention to seeing the tumor bed.
The same positioning, wiring and scan used for whole-breast treatment. More →
Supine on a breast board (or prone), arms up, with breath hold considered to reduce heart and lung dose.
Small metal clips left in the walls of the lumpectomy cavity at surgery.
The tumor bed is drawn around the clips and any change in the surrounding tissue. A tumor bed that can't be clearly seen makes partial breast treatment unsuitable.
Image fusion aligns an outside scan with the planning CT so the target can be drawn using information the CT doesn't show. As for whole-breast treatment, any available pre-operative imaging — mammogram, ultrasound, MRI or PET/CT.
The whole partial-breast target is built around the tumor bed, so the pre-operative imaging helps confirm the bed is drawn in the right place. The bed itself is contoured on the planning CT from the clips and post-operative change; the breast's shape differs between the scans, so check any registration locally.
What each volume represents. Expansions come from your protocol.
The volume around the surgical clips and any change in the surrounding tissue architecture.
Every other target is built from it, so errors here carry through the whole plan.
The tumor bed expanded to cover microscopic disease, trimmed back from the skin and limited by the chest wall muscle.
It defines how much breast is treated; the uninvolved breast is everything outside it.
The CTV expanded for setup uncertainty, and an evaluation copy cropped away from the skin and limited by the pectoral muscle.
Coverage and hotspots are judged on PTV_Eval, which excludes the skin and build-up region where full dose isn't expected.
Click an organ for its anatomy, why it matters and contouring resources. Superscripts link to the source behind each value.
| Organ | All schedules40.05 Gy/15 fx · 30 Gy/5 fx · 26 Gy/5 fx |
|---|---|
| Uninvolved Ipsilateral BreastIpsilateral breast tissue minus PTV. | |
| Ipsilateral Lung |
|
| Contralateral Lung | |
| Heart / PericardiumVolume goals also apply and differ by side. | |
| LAD (Left Anterior Descending Artery)Keep as low as possible; no numeric limit found for partial breast. | — |
| Contralateral Breast |
|
| Thyroid |
|
Values quoted from eviQ 3658 (last reviewed 28 March 2024; review due 30 June 2028), checked by DoseLab on 2026-09-23. Verify against your protocol, institutional policy and physician directive before clinical use.
Five-year results of the UK IMPORT LOW trial comparing partial-breast with whole-breast radiotherapy. Citation as given in the eviQ reference list; not yet checked against the journal.
ASTRO clinical practice guideline on partial breast irradiation. eviQ takes all of its partial-breast organ goals from this guideline's planning table. Citation as given in the eviQ reference list; not yet checked against the journal.
Five-year results of the UK FAST-Forward trial, comparing one week of whole-breast or chest wall radiotherapy with three weeks. Citation as given in the eviQ reference list; not yet checked against the journal.
NRG Oncology's breast downloads page, which links the RTOG Breast Cancer Atlas for Radiation Therapy Planning, an NRG whole-breast radiation therapy template and the RADCOMP breast atlas.
Endorsed eviQ protocol for external-beam partial breast irradiation. Its organ goals are all taken from the 2023 ASTRO partial breast guideline and are expressed as a percentage of the prescription, so one set applies to every schedule. DoseLab's partial breast table reproduces selected values.