Loading
Treating only the part of the breast around the tumour worked as well as treating all of it, but giving the dose twice a day made the breast look worse years later. The lesson is about the timetable, not the target.
RAPID randomised 2,135 women aged 40 or over with ductal carcinoma in situ or node-negative breast cancer at 33 centres in Canada, Australia and New Zealand between 2006 and 2011, to external beam accelerated partial-breast irradiation of 38.5 Gy in ten fractions given twice daily over five to eight days, or to whole-breast irradiation of 42.5 Gy in sixteen or 50 Gy in twenty-five daily fractions.
At a median 8.6 years, the eight-year cumulative rate of ipsilateral breast tumour recurrence was 3.0 percent with partial-breast treatment (95 percent confidence interval 1.9 to 4.0) and 2.8 percent with whole-breast treatment (1.8 to 3.9), a hazard ratio of 1.27 (90 percent confidence interval 0.84 to 1.91), which met the pre-specified non-inferiority margin.
The toxicity split in two directions. Acute grade 2 or worse toxicity was less common with partial-breast treatment, 28 against 45 percent (p<0.0001). Late grade 2 or worse toxicity was much more common, 32 against 13 percent (p<0.0001), and adverse cosmesis was more common at three years (absolute difference 11.3 percent), five years (16.5 percent) and seven years (17.7 percent).
The trial's own interpretation is that the twice-daily timetable, not the smaller volume, is the likely cause, and that once-daily partial-breast schedules should be studied. IMPORT LOW, which delivered partial-breast treatment once a day in fifteen fractions with ordinary tangential fields, found fewer changes in breast appearance than whole-breast treatment, which supports that reading. The record is marked mixed because the cancer endpoint was met and the cosmetic endpoint was not.
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.
2,135 enrolled.
95 percent confidence interval 1.9 to 4.0 · 95 percent confidence interval 1.8 to 3.9
Source| Endpoint | Arm | n | Value | HR (95% CI) | p | Source |
|---|---|---|---|---|---|---|
| Ipsilateral breast tumour recurrence at 8 yearsprimary | Accelerated partial-breast irradiation, 38.5 Gy in 10 twice-daily fractions | 1,070 | 3% | 1.27 (0.84 to 1.91) | - | link |
| Whole-breast irradiation | 1,065 | 2.8% | ||||
| Late radiation toxicity, grade 2 or worse | Accelerated partial-breast irradiation | 1,070 | 32% | - | <0.0001 | link |
| Whole-breast irradiation | 1,065 | 13% |
Shares IMPORT LOW, Partial-breast irradiation, Hypofractionation (fewer, larger radiotherapy doses), HER2-positive breast cancer.
Shares Partial-breast irradiation, Hypofractionation (fewer, larger radiotherapy doses), Hypofractionated radiotherapy, HER2-positive breast cancer.
Shares Partial-breast irradiation, Hypofractionation (fewer, larger radiotherapy doses), Hypofractionated radiotherapy, HER2-positive breast cancer.
Shares IMPORT LOW, Hypofractionated radiotherapy, HER2-positive breast cancer, Breast cancer (all types).
Shares Hypofractionation (fewer, larger radiotherapy doses), Hypofractionated radiotherapy, HER2-positive breast cancer, Breast cancer (all types).
Shares Partial-breast irradiation, Hypofractionation (fewer, larger radiotherapy doses), HER2-positive breast cancer, Breast cancer (all types).
Shares Hypofractionation (fewer, larger radiotherapy doses), Hypofractionated radiotherapy, HER2-positive breast cancer, Breast cancer (all types).
Shares Ductal carcinoma in situ (DCIS), HER2-positive breast cancer, Triple-negative breast cancer (TNBC), HR-positive / HER2-negative breast cancer.