The overwhelming majority of postmenopausal patients aged 50 to 69 years with favorable-risk stage I hormone receptor–positive (HR+) breast cancer who opted out of radiation therapy were disease-free 5 years after surgery, according to results of the IDEA trial. Among 186 evaluable patients who were on endocrine therapy for 5 years, 100% were alive 5 years after lumpectomy, and 99% were breast cancer–free at the time results were presented at the 2023 San Antonio Breast Cancer Symposium by lead author Reshma Jagsi, MD, Emory University School of Medicine and Winship Cancer Institute, and published simultaneously in the Journal of Clinical Oncology.1
Women enrolled in the trial were identified as low risk according to the Oncotype DX Recurrence Score. “This is the first trial to combine a genomic assay and endocrine therapy and to consider younger post-menopausal women aged 50 to 69 years with favorable-risk stage I [HR+] breast cancer for omission of radiotherapy. The omission of radiotherapy plus 5 years of endocrine therapy achieved very low rates of recurrence using the 21-gene [Oncotype DX] recurrence score in combination with classic clinical and biological features for radiation selection. Although 5 years is an early timepoint for these women, long-term follow-up will help determine whether the option of avoiding initial radiation can be offered to a broader range of women than recommended in current guidelines,” stated Dr Jagsi.
“But up till now, trials in younger patients have been equivocal, and it remains unclear whether younger patients can safely opt out of adjuvant radiotherapy,” Dr Jagsi noted. The IDEA trial was designed to shed light on this issue.
Study Description
The prospective, single-arm IDEA trial was conducted at 13 sites and included women with stage I breast cancer and negative surgical margins following lumpectomy. Women were aged 50 to 69 (median age, 63) years and had unifocal, HR+/HER2-negative, node-negative stage I disease. Surgical margins were 2 mm or larger.
The Oncotype DX Recurrence Score was used to determine risk of recurrence based on the genetic profile of each participant’s tumor. A recurrence score of ≤18 was used to select women for omission of radiotherapy after breast-conserving surgery. Those with a recurrence score of ≤18 (n=200) were eligible to omit radiotherapy after breast-conserving surgery, but they were treated with standard-of-care adjuvant endocrine therapy for ≥5 years. Median follow-up was 5.2 years.
At 5 years, 2 ipsilateral recurrences were reported. In addition, 6 recurrences were reported after 5 years. There were no distant recurrences. The crude rates of ipsilateral recurrence were 5% for patients aged 50 to 59 years and 3.6% for those aged 60 to 69 years.
Dr Jagsi cautioned listeners about the characteristics of patients enrolled in the study. “Don’t generalize these findings to patients with less-extensive surgery than the pathological nodal evaluation and margin requirements of this study. Also, exercise caution if compliance to endocrine therapy is not assured.
“The take-away message from this trial is that younger post-menopausal women who meet the criteria of the IDEA trial should be enrolled in clinical trials. Newer radiation techniques have much lower toxicity, and we don’t want the headline of the news to scare off women from radiation therapy. If the recurrence score is high and/or you have an indication that the disease is aggressive, you should offer radiotherapy,” she added.
Reference
- Jagsi R, Griffith KA, Harris EE, et al. Omission of radiotherapy after breast-conserving surgery for women with breast cancer with low clinical and genomic risk: 5-year outcomes of IDEA. J Clin Oncol. 2024;42:390-398.