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An extra dose of radiotherapy aimed at the place the lump came from cuts the chance of the cancer returning in that breast by about a third, but it does not help anyone live longer and it triples the chance of the breast becoming hard and scarred. That trade is the reason the extra dose is offered by risk rather than to everybody.
Between 1989 and 1996, EORTC 22881-10882 randomised 5,318 patients with stage I or II breast cancer, all of whom had a microscopically complete excision and 50 Gy of whole-breast irradiation over five weeks, to a further 16 Gy to the tumour bed or to nothing further. Overall survival was the primary endpoint. The twenty-year report is the one to read.
At a median 17.2 years, twenty-year overall survival was 59.7 percent with the boost and 61.1 percent without it (hazard ratio 1.05, 99 percent confidence interval 0.92 to 1.19, p=0.323): the boost does not change how long people live. What it changes is local control. Ipsilateral breast tumour recurrence was the first failure in 354 patients (13 percent) without the boost and 237 (9 percent) with it (hazard ratio 0.65, 99 percent confidence interval 0.52 to 0.81, p<0.0001), a twenty-year cumulative incidence of 16.4 against 12.0 percent. About three-quarters of those recurrences led to a mastectomy in both arms.
The cost is measurable and permanent: the twenty-year cumulative incidence of severe fibrosis was 1.8 percent without the boost and 5.2 percent with it (p<0.0001). The trial's own conclusion is that the absolute benefit is largest in young patients and that the extra dose can be avoided in most patients over 60. NICE NG101 recommendation 1.13.17 offers a boost to women at high risk of local recurrence, and 1.13.18 requires that the side effects be explained.
Numbers are from the trial as recorded here; see the source links in the table below. This is orientation, not medical advice: ask your team how closely the trial population matches you.
5,318 randomised.
99 percent confidence interval 56.3 to 63.0 · 99 percent confidence interval 57.6 to 64.3
Source99 percent confidence interval 9.8 to 14.4 · 99 percent confidence interval 14.1 to 18.8
Source99 percent confidence interval 3.9 to 6.4 · 99 percent confidence interval 1.1 to 2.5
Source| Endpoint | Arm | n | Value | HR (95% CI) | p | Source |
|---|---|---|---|---|---|---|
| Overall survival at 20 yearsprimary | 16 Gy tumour-bed boost | 2,661 | 59.7% | 1.05 | 0.323 | link |
| No boost | 2,657 | 61.1% | ||||
| Cumulative incidence of ipsilateral breast tumour recurrence at 20 years | 16 Gy tumour-bed boost | 2,661 | 12% | 0.65 | <0.0001 | link |
| No boost | 2,657 | 16.4% | ||||
| Cumulative incidence of severe fibrosis at 20 years | 16 Gy tumour-bed boost | 2,661 | 5.2% | - | <0.0001 | link |
| No boost | 2,657 | 1.8% |
Shares EORTC 10801, Lumpectomy (breast-conserving surgery), Resection margins (R0 / R1 / R2), HER2-positive breast cancer.
Shares IMPORT LOW, Hypofractionated radiotherapy, HER2-positive breast cancer, Breast cancer (all types).
Shares EORTC 10801, Lumpectomy (breast-conserving surgery), Resection margins (R0 / R1 / R2), HER2-positive breast cancer.
Shares Tumour bed boost, IMPORT LOW, Lumpectomy (breast-conserving surgery), HER2-positive breast cancer.
Shares IMPORT LOW, Lumpectomy (breast-conserving surgery), HER2-positive breast cancer, Breast cancer (all types).
Shares EORTC 10801, Lumpectomy (breast-conserving surgery), HER2-positive breast cancer, Breast cancer (all types).
Shares Tumour bed boost, Lumpectomy (breast-conserving surgery), HER2-positive breast cancer, Breast cancer (all types).
Shares Hypofractionated radiotherapy, HER2-positive breast cancer, Breast cancer (all types), IMRT / IGRT (modern external beam).