Breast
The case for a DCIS boost was extrapolated from invasive disease (EORTC boost). BIG 3-07/TROG 07.01 now tests it in a randomised trial in DCIS after BCS with ≥1 mm margins.
BIG 3-07/TROG 07.01 NCT00470236
ForNon-low-risk DCIS after BCS, ≥1 mm clear radial margins
TL;DRTumour bed boost after WBI in resected non-low-risk DCIS: 5-yr freedom from LR 97.1% vs 92.7%, HR 0.47 (0.31-0.72), p<0.001.
The boost gain held on a 42.5 Gy/16 fx WBI backbone as well as 50 Gy/25 fx, so boost is not tied to conventional fractionation. The cost is G2+ induration 14% vs 6%, which is the number to weigh when deciding boost vs omission after ≥1 mm margins in non-low-risk DCIS.
In a woman with resected non-low-risk DCIS and ≥1 mm margins planned for WBI, this supports offering a 16 Gy/8 fx boost against a higher G2+ induration and pain rate; it does not address low-risk DCIS or pts with <1 mm margins.
Boost 16 Gy/8 fx cut LR hazard (HR 0.47) on both 50 Gy/25 fx and 42.5 Gy/16 fx WBI backbones, so it transfers to hypofractionated practice. The trade is G2+ induration 14% vs 6%, which frames the boost-or-omit conversation in non-low-risk DCIS with ≥1 mm margins.
7 details 4 trials watching
International randomised, unmasked, factorial phase 3, 136 centres across six trial groups in 11 countries. N=1608 accrued 2007-2014; median f/u 6.6 yr.
Women ≥18y with unilateral, histologically proven non-low-risk DCIS after breast-conserving surgery with ≥1 mm clear radial margins.
WBI either 50 Gy/25 fx (n=831) or 42.5 Gy/16 fx (n=777), randomised in a 4-arm factorial or chosen per centre. Boost 16 Gy/8 fx to tumour bed after WBI.
Primary: time to local recurrence. Toxicity reported as G2+ breast pain and induration.
Boost raised G2+ breast pain (14% vs 10%, p=0.003) and G2+ induration (14% vs 6%, p<0.001).
Older DCIS trials (NSABP B-17, EORTC 10853) established WBI after lumpectomy but did not test boost; the EORTC boost trial tested it only in invasive disease. This is the first randomised boost evidence in DCIS.
The fractionation-sensitivity result is not reported in the source abstract, so hypofractionation non-inferiority in DCIS cannot be read from it. Toxicity is assessor-unmasked, and no survival endpoint is reported.
A boost roughly halves local recurrence hazard in non-low-risk DCIS at a real cost in G2+ breast morbidity. It does not settle which non-low-risk subsets carry enough baseline risk to justify that trade.
CONSORT flow
Adequately powered phase 3 RCT, primary endpoint hit with 6.6-yr median f/u; first randomised boost data in DCIS. Qualified by unmasked design and added G2+ toxicity.
- Which non-low-risk DCIS subsets derive most boost benefit
- Local recurrence with hypofractionated vs conventional WBI in DCIS n=301 · primary completion 2020-11 · randomised hypo vs standard WBI, DCIS eligiblen=72 · primary completion 2026-12 · 1-wk vs 3.1-wk WBI, DCIS eligible, local control EP
- Boost role with ultra-hypofractionated or partial-breast RT recruiting Ultra Hypo-fractionated Adjuvant Whole Breast Radiation Therapy With Simultaneous Integrated Boost for Early-Stage Breast Cancer (H-ASSIST) Phase 2n=90 · primary completion 2028-02 · 5-fx WBI + SIB tumour bed boost, DCIS includedrecruiting 5 vs. 9-day Course of Whole Breast Radiotherapy With Boost for Early-stage Breast Cancer Phase 2n=144 · primary completion 2030-05 · randomised 5 vs 9 day WBI with boost, DCIS eligible