{"entity":{"id":"rapid","kind":"trial","name":"RAPID (accelerated partial-breast irradiation)","aka":["RAPID trial","OCOG RAPID"],"tldr":"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.","summary":"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.\n\nAt 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.\n\nThe 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).\n\nThe 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.","status":"mixed","asOf":"2026-09-25","links":[{"label":"ClinicalTrials.gov NCT00282035","url":"https://clinicaltrials.gov/study/NCT00282035"},{"label":"RAPID (The Lancet 2019)","url":"https://doi.org/10.1016/S0140-6736(19)32515-2"}],"tags":[],"related":[],"cancers":["breast-cancer","breast-hr-positive","breast-her2-positive","tnbc","ductal-carcinoma-in-situ"],"sections":[],"technologies":["imrt-igrt","hypofractionated-radiotherapy"],"targets":[],"drugs":[],"companies":["cctg"],"institutions":[],"pathways":[],"terms":["partial-breast-irradiation","hypofractionation"],"trials":["import-low","nsabp-b39","targit-a"],"people":[],"bottlenecks":[],"keyPapers":[],"journals":[],"dependsOn":[],"notes":[],"nct":"NCT00282035","phase":"3","setting":"Women aged 40 or over with ductal carcinoma in situ or node-negative breast cancer after breast-conserving surgery: external beam accelerated partial-breast irradiation of 38.5 Gy in ten fractions twice a day over five to eight days, against whole-breast irradiation, with ipsilateral breast tumour recurrence as the primary endpoint","sponsor":"Ontario Clinical Oncology Group","result":"Eight-year ipsilateral breast tumour recurrence 3.0 percent with twice-daily partial-breast irradiation against 2.8 percent with whole-breast irradiation (non-inferior), with late toxicity 32 against 13 percent and adverse cosmesis 17.7 percentage points more common at seven years.","yearReported":2019,"enrolled":2135,"enrolledBasis":"registry","outcomes":[{"endpoint":"Ipsilateral breast tumour recurrence at 8 years","primary":true,"unit":"%","arms":[{"name":"Accelerated partial-breast irradiation, 38.5 Gy in 10 twice-daily fractions","n":1070,"value":3,"note":"95 percent confidence interval 1.9 to 4.0"},{"name":"Whole-breast irradiation","n":1065,"value":2.8,"note":"95 percent confidence interval 1.8 to 3.9"}],"hr":1.27,"ci":[0.84,1.91],"source":"https://doi.org/10.1016/S0140-6736(19)32515-2"},{"endpoint":"Late radiation toxicity, grade 2 or worse","unit":"%","arms":[{"name":"Accelerated partial-breast irradiation","n":1070,"value":32},{"name":"Whole-breast irradiation","n":1065,"value":13}],"p":"<0.0001","source":"https://doi.org/10.1016/S0140-6736(19)32515-2"}],"replication":"IMPORT LOW and NSABP B-39/RTOG 0413 tested partial-breast irradiation in the same population with different schedules and reached different conclusions about cosmesis, so the schedule, not the idea of treating part of the breast, is what the three trials disagree about."},"route":"/trials/rapid/","neighbours":{"cancer":[{"id":"breast-cancer","kind":"cancer","name":"Breast cancer (all types)","route":"/cancers/breast-cancer/"},{"id":"ductal-carcinoma-in-situ","kind":"cancer","name":"Ductal carcinoma in situ (DCIS)","route":"/cancers/ductal-carcinoma-in-situ/"},{"id":"breast-her2-positive","kind":"cancer","name":"HER2-positive breast cancer","route":"/cancers/breast-her2-positive/"},{"id":"breast-hr-positive","kind":"cancer","name":"HR-positive / HER2-negative breast cancer","route":"/cancers/breast-hr-positive/"},{"id":"tnbc","kind":"cancer","name":"Triple-negative breast cancer (TNBC)","route":"/cancers/tnbc/"}],"technology":[{"id":"hypofractionated-radiotherapy","kind":"technology","name":"Hypofractionated radiotherapy","route":"/technologies/hypofractionated-radiotherapy/"},{"id":"imrt-igrt","kind":"technology","name":"IMRT / IGRT (modern external beam)","route":"/technologies/imrt-igrt/"}],"company":[{"id":"cctg","kind":"company","name":"Canadian Cancer Trials Group (CCTG)","route":"/companies/cctg/"}],"term":[{"id":"hypofractionation","kind":"term","name":"Hypofractionation (fewer, larger radiotherapy doses)","route":"/terms/hypofractionation/"},{"id":"partial-breast-irradiation","kind":"term","name":"Partial-breast irradiation","route":"/terms/partial-breast-irradiation/"}],"trial":[{"id":"import-low","kind":"trial","name":"IMPORT LOW","route":"/trials/import-low/"},{"id":"nsabp-b39","kind":"trial","name":"NSABP B-39/RTOG 0413","route":"/trials/nsabp-b39/"},{"id":"targit-a","kind":"trial","name":"TARGIT-A (targeted intraoperative radiotherapy)","route":"/trials/targit-a/"}]}}