Omission of Radiotherapy After Breast-Conserving Surgery for Women With Breast Cancer With Low Clinical and Genomic Risk: 5-Year Outcomes of IDEA
Reshma Jagsi, Kent A. Griffith, Eleanor Harris, Jean L. Wright, Abram Recht, Alphonse G. Taghian, Lucille Lee, Meena S. Moran, William Small, Candice Johnstone, Asal Rahimi, Gary M. Freedman, Mahvish Muzaffar, Bruce G. Haffty, Kathleen C. Horst, Simon N. Powell, Jody Sharp, Michael S. Sabel, Anne F. Schott, Mahmoud El‐Tamer
Abstract
PURPOSE: Multiple studies have shown a low risk of ipsilateral breast events (IBEs) or other recurrences for selected patients age 65-70 years or older with stage I breast cancers treated with breast-conserving surgery (BCS) and endocrine therapy (ET) without adjuvant radiotherapy. We sought to evaluate whether younger postmenopausal patients could also be successfully treated without radiation therapy, adding a genomic assay to classic selection factors. METHODS: Postmenopausal patients age 50-69 years with pT1N0 unifocal invasive breast cancer with margins ≥2 mm after BCS whose tumors were estrogen receptor-positive, progesterone receptor-positive, and human epidermal growth factor receptor 2-negative with Oncotype DX 21-gene recurrence score ≤18 were prospectively enrolled in a single-arm trial of radiotherapy omission if they consented to take at least 5 years of ET. The primary end point was the rate of locoregional recurrence 5 years after BCS. RESULTS: Between June 2015 and October 2018, 200 eligible patients were enrolled. Among the 186 patients with clinical follow-up of at least 56 months, overall and breast cancer-specific survival rates at 5 years were both 100%. The 5-year freedom from any recurrence was 99% (95% CI, 96 to 100). Crude rates of IBEs for the entire follow-up period for patients age 50-59 years and age 60-69 years were 3.3% (2/60) and 3.6% (5/140), respectively; crude rates of overall recurrence were 5.0% (3/60) and 3.6% (5/140), respectively. CONCLUSION: This trial achieved a very low risk of recurrence using a genomic assay in combination with classic clinical and biologic features for treatment selection, including postmenopausal patients younger than 60 years. Long-term follow-up of this trial and others will help determine whether the option of avoiding initial radiotherapy can be offered to a broader group of women than current guidelines recommend.