Type of publication:
Conference abstract
Author(s):
Coles C., *Agrawal R., Ah-See M.L., Algurafi H., Alhasso A., Brunt A.M., Chan C., Griffin C., Harnett A., Hopwood P., Kirby A., Sawyer E., Syndikus I., Titley J., Tsang Y., Wheatley D., Wilcox M., Yarnold J., Bliss J.M.
Citation:
European Journal of Cancer, April 2016, vol./is. 57/(S4)
Abstract:
Background: IMPORT LOW is a randomised, multi-centre phase III trial testing partial breast radiotherapy (RT) using intensity modulated RT in women with low risk early stage breast cancer, for whom late complications of RT are the dominant hazard rather than local recurrence (LR). Materials and Methods: Women age >50 who had breast conservation surgery, for invasive adenocarcinoma (excluding classical lobular carcinoma) pT1-2 (<3 cm) N0-1, any grade, with minimum microscopic margins of ge;2 mm, were eligible. Patients were randomised (1:1:1) to 40Gy/15F to whole breast (control); 36Gy/15F to whole breast and 40Gy/15Fr to partial breast (test 1); or 40Gy/15F to partial breast (test 2). The primary endpoint is local tumour control in the ipsilateral breast. 1935 patients were required to exclude 2.5% inferiority for each test group (80% power, one-sided alpha 2.5%) assuming 2.5% local recurrence (LR) rate at 5 years in the control group. Key secondary endpoints were late adverse effects measured using a combination of clinical, photographic and patient self-assessments. Analysis was by intention to treat. Results: 2018 patients were recruited from 05/2007 to 09/2010 from 30 UK RT centres (675 control, 674 test 1, 669 test 2). Baseline characteristics were balanced with median age 63 (IQR 58-68); 43%, 47% and 10% were tumour grade 1, 2 and 3; 3% were pN+. Median follow-up is 68.3 (IQR 60.3-73.4) months. The 5-year rate of LR was 1.1% (95% CI 0.5, 2.3), 0.2% (95% CI 0.02, 1.2) and 0.5% (95% CI 0.2-1.4) in the control, test 1 and test 2 groups respectively. Absolute treatment differences in LR with control compared with test 1 is -0.83% (95% CI -1.04, 0.18) and -0.69% (-0.99, 0.44) compared with test 2. For each of the test groups non-inferiority, assessed against the pre-specified 2.5% threshold was demonstrated. Conclusions: At 5 years, partial breast RT was shown to be non-inferior to whole breast RT in women with low risk early breast cancer. LR rates were very low in all treatment groups and moderate and marked normal tissue events were also low across all groups. Follow-up is ongoing and 10 year LR rates will be reported. (Figure Presented).