Radiotherapy Omission Among Younger, Postmenopausal Patients With PT1N0 Unifocal Breast Cancer and Favorable Tumor Biology

Long-term follow-up results from the IDEA study suggest that younger postmenopausal patients with PT1N0 unifocal invasive breast cancer harboring favorable biological features can potentially omit radiotherapy and experience high disease control when breast-conserving surgery is followed by endocrine therapy alone.

“Multiple studies have shown a low risk of ipsilateral breast events (IBEs) or other recurrences for selected patients aged 65-70 years or older with stage I breast cancers treated with breast-conserving surgery and endocrine therapy without adjuvant radiotherapy,” stated Reshma Jagsi, MD, DPhil, Emory University, Atlanta, Georgia, and coauthors. In the current analysis, researchers “evaluate whether younger postmenopausal patients could also be successfully treated without radiation therapy, adding a genomic assay to classic selection factors.” 

In this study, 200 postmenopausal patients aged 50 to 69 years with pT1N0 unifocal invasive breast cancer with estrogen receptor (ER)-positive, progesterone receptor (PR)-positive, and human epidermal growth factor receptor 2 (HER2)-negative tumors with an Oncotype DX 21-gene recurrence score ≤18 were enrolled into a single-treatment arm. Within 90 days of breast-conservation surgery, 186 patients with post-surgical margins ≥2 mm underwent at least 5 years of endocrine therapy without radiotherapy followed by 10 years of surveillance. The primary end point was rate of locoregional recurrence 5-years post–breast-conserving surgery.

At a median follow-up of 56 months, overall and breast cancer specific survival rates were 100% and the 5-year freedom from any recurrence was 99% (2 isolated ipsilateral axillary recurrences occurred at 21 and 49 months). Crude rates of IBEs for the entire follow-up period was 3.3% for patients aged 50 to 59 and 3.6% for patients aged 60 to 69. Crude rates of overall recurrence were 5% and 3.6%, respectively.

Dr Jagsi and coauthors concluded, “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.” 

“The IDEA trial highlights the impact of tumor biology, providing support for the ongoing DEBRA trial and foreshadowing a future of even more individualized treatment decisions,” added Journal of Clinical Oncology Senior Deputy Editor Kathy D. Miller, MD, Indiana School of Medicine, Indianapolis. 

Source: 

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. Published online: December 7, 2023. doi:10.1200/JCO.23.02270