Abstract ES4-1: Which patients can safely avoid radiation after breast conserving surgery?
Authors: Kunkler Ian H. 
Published: May 2015

Abstract
Whether or not there is a subgroup of patients from whom adjuvant RT can be safely omitted after breast conserving surgery (BCS) for invasive breast cancer (IBC) remains controversial. The Oxford overview (1) shows that whole breast RT (WBRT) after BCS for IBC halves the risk of first recurrence. However the absolute reduction in ipsilateral breast tumour recurrence (IBTR) in ER+ older patients is modest.Guidelines on the omission of RT after BCS vary. The issue is complicated by falling IBTR rates after BCS, adjuvant endocrine therapy (AET) and RT, now around 2-3% at 5 years. The CALGB 9343 trial in women with T1, ER+ tumours receiving tamoxifen and randomized to WBRT or not showed a 3% reduction in local recurrence at 5 years from RT (1% vs 4%,p=&lt;0.001) [2] At a median follow up of 10.5 years the difference in local recurrence had widened in favour of RT (2% RT+, 9% RT-)[3].The PRIME 2 trial randomised 1326 patients with T1-T2 (up to 3cm), pNO, hormone receptor positive tumours =/&gt;65 years after BCS and AET to WBRT or no WBRT. It showed a 2.8% reduction in IBTR from RT (4.1% vs 1.3%,p=0.002) at a median follow up of 5 years(4). An unplanned subgroup analysis by ER status showed a 2.1% reduction in local recurrence (1.2% RT+, 3.3% RT-) from RT but should be interpreted cautiously. However omission of WBRT might be discussed with such patients as an option. Modest absolute improvements in local control from WBRT have to be balanced against increased rates of major coronary events (5).The risk of IBTR is influenced by local therapy, systemic therapy and biology (6).To refine selection of low risk patients, molecular markers of low risk are needed. If molecular signatures of radiosensitivity for breast cancer (7) can be validated from mature RCTs of BCS +/RT, selection of patients cured by surgery and adjuvant endocrine therapy alone could be strengthened.
References:
1. Darby S, McGale P,Correa P et al. Effect of radiotherapy after breast conserving surgery on 10-year recurrence and 15 year breast cancer death: meta-analysis of individual patient data for 10,801 women in 17 randomised trials.Lancet 2011;378:1707-16.
2. Hughes KS, Schnaper LA, Berry D et al. Lumpectomy plus tamoxifen with or without irradiation in women 70 years or older with early breast cancer. N Engl J Med 2004;351:97-7.
3. Hughes KS, Schnaper LA, Bellon JR et al. Lumpectomy plus tamoxifen with or without irradiation in women aged 70 years or older with early breast cancer.Long term follow up of CALGB 9343. J Clin Oncol 2013;31:2382-2387.
4. Kunkler IH, Williams LW, Jack W et al. The PRIME 2 trial: wide local excision and adjuvant hormonal therapy +/- postoperative whole breast irradiation in women in women =/&gt; 65 years with early breast cancer. 2013 San Antonio Breast Cancer Symposium. Abstract S2-01.
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7. Speers C ,Balbin OA, Liu M et al. RadiotypeDX:identification and validation of a radiation sensitivity signature in human breast cancer.2013 San Antonio Breast Cancer Symposium. Abstract P6-06-05.
Citation Format: Ian H. Kunkler. Which patients can safely avoid radiation after breast conserving surgery? [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr ES4-1.