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Treating only the part of the breast around where the lump was, instead of the whole breast, on the grounds that almost all recurrences happen there. It works, but which schedule is used decides whether the breast looks better or worse afterwards.
Four randomised trials tested the idea and the disagreement between them is about delivery, not about the target.
IMPORT LOW randomised 2,018 women to whole-breast radiotherapy, whole-breast with reduced dose outside the tumour bed, or partial-breast treatment only, all 40 Gy in fifteen fractions using ordinary tangential fields simply shortened. Five-year local relapse was 0.5 percent with partial-breast treatment against 1.1 percent with whole-breast, non-inferior, with fewer reported changes in breast appearance. RAPID randomised 2,135 women to 38.5 Gy in ten fractions given twice a day: the eight-year recurrence rate was non-inferior at 3.0 against 2.8 percent, but late grade 2 or worse toxicity was 32 against 13 percent and adverse cosmesis was 17.7 percentage points more common at seven years. NSABP B-39/RTOG 0413 randomised 4,216 women to twice-daily partial-breast treatment by brachytherapy or external beam and found ten-year recurrence of 4.6 against 3.9 percent, a small absolute difference whose confidence interval crossed the equivalence margin, so equivalence was not established. TARGIT-A gave a single dose during the operation itself and met its non-inferiority margin, with five-year local recurrence of 2.11 against 0.95 percent.
The pattern is that once-daily external beam partial-breast treatment matches whole-breast treatment on both cancer control and appearance, while twice-daily schedules match on cancer control and lose on appearance. That is why NICE NG101 recommendation 1.13.6 says to use external beam radiotherapy when giving partial-breast treatment.
England restricts who is offered it. NICE NG101 recommendation 1.13.4 considers partial-breast radiotherapy for women who have had breast-conserving surgery for invasive cancer excluding lobular type, with clear margins, a low absolute risk of local recurrence defined as aged 50 or over with tumours of 3 cm or less, node-negative, oestrogen receptor-positive, HER2-negative and grade 1 to 2, and who will take endocrine therapy for at least five years. Recommendation 1.13.5 requires the discussion to say that five-year local recurrence is equivalent to whole-breast treatment, that the risk beyond five years is not yet known, and that late adverse effects may be fewer. Intraoperative radiotherapy is separately not recommended for routine commissioning by NICE TA501.
An open problem has appeared since the axillary de-escalation trials reported: every partial-breast trial required pathological nodal staging as part of its eligibility, and women who now have no sentinel node biopsy therefore fall outside the evidence.
Showing the technology this term belongs to: IMRT / IGRT (modern external beam).
Shares Tumour bed boost, IMPORT LOW, Lumpectomy (breast-conserving surgery), HER2-positive breast cancer.
Shares START-B (UK Standardisation of Breast Radiotherapy), FAST-Forward, Hypofractionation (fewer, larger radiotherapy doses), HER2-positive breast cancer.
Shares START-B (UK Standardisation of Breast Radiotherapy), FAST-Forward, Hypofractionation (fewer, larger radiotherapy doses), HER2-positive breast cancer.
Shares Leaving radiotherapy out, FAST-Forward, Hypofractionation (fewer, larger radiotherapy doses), HER2-positive breast cancer.
Shares Tumour bed boost, Lumpectomy (breast-conserving surgery), HER2-positive breast cancer, Breast cancer (all types).
Shares Leaving radiotherapy out, Lumpectomy (breast-conserving surgery), HER2-positive breast cancer, Breast cancer (all types).
Shares IMPORT LOW, RAPID (accelerated partial-breast irradiation), START-B (UK Standardisation of Breast Radiotherapy), FAST-Forward.
Shares Ductal carcinoma in situ (DCIS), HER2-positive breast cancer, Triple-negative breast cancer (TNBC), HR-positive / HER2-negative breast cancer.