As reported in the Journal of Clinical Oncology by Reshma Jagsi, MD, DPhil, and colleagues, a 5-year analysis of the IDEA trial showed a very low rate of recurrence with the omission of radiotherapy after breast-conserving surgery in patients at low clinical and genomic risk for disease recurrence.
Reshma Jagsi, MD, DPhil
Study Details
In the U.S. multicenter study, 200 patients who received no radiotherapy if they consented to ≥ 5 years of endocrine therapy were enrolled between June 2015 and October 2018. The study included postmenopausal women aged 50 to 69 years with pT1N0 unifocal invasive breast cancer and margins ≥ 2 mm after breast-conserving surgery. For inclusion in the study, patients had to have estrogen receptor–positive, progesterone receptor–positive, HER2-negative tumors; an Oncotype DX 21-gene recurrence score ≤ 18; and could not be a carrier of a known breast cancer predisposition mutation. The primary outcome measure was rate of locoregional recurrence at 5 years after breast-conserving surgery.
Key Findings
Median follow-up was 5.21 years (interquartile range = 5.01–5.97 years). The mean 21-gene recurrence score was 11.2. Tumors were grade 1 in 85 patients, grade 2 in 109, and grade 3 in 6. Mean tumor size was 10 mm. Lymphovascular invasion was present in 16 patients, and an extensive intraductal component was present in 11.
Among 186 patients with follow-up of at least 56 months, 5-year rates of overall survival and breast cancer–specific survival were both 100%. Five-year freedom from any disease recurrence was 99% (95% confidence interval [CI] = 96%–100%). Of the two patients with events occurring within 5 years, one had an isolated ipsilateral axillary recurrence at 21 months, and the other had an ipsilateral breast event at 49 months.
Six additional patients had a recurrence at > 5 years after breast-conserving surgery, including five with ipsilateral breast events and one with an ipsilateral breast event plus a regional recurrence. No distant recurrences were observed. Crude rates of ipsilateral breast events for the entire follow-up period were 3.3% (2 of 60 patients) for patients aged 50 to 59 years, and 3.6% (5 of 140 patients) for those aged 60 to 69 years. Crude rates of overall recurrence were 5.0% (3 of 60 patients) and 3.6% (5 of 140 patients), respectively.
The investigators concluded, “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.”
Dr. Jagsi, of the Department of Radiation Oncology, Winship Cancer Institute of Emory University, Atlanta, is the corresponding author for the Journal of Clinical Oncology article.
Disclosure: The study was supported by the Susan G. Komen Foundation and others. For full disclosures of the study authors, visit ascopubs.org.
