Younger postmenopausal patients with early-stage breast cancer may be able to safely omit adjuvant radiotherapy

Almost all postmenopausal patients aged 50-–69 years with stage I hormone receptor (HR)-positive breast cancer and low scores on a common genetic test who opted out of adjuvant radiotherapy were disease free five years after surgery, according to results from the IDEA clinical trial presented at the San Antonio Breast Cancer Symposium, held December 5–9, 2023.

Results were simultaneously published in the Journal of Clinical Oncology.

Patients who are diagnosed with stage I HR-positive breast cancer typically undergo breast-conserving surgery followed by adjuvant radiotherapy and endocrine therapy to reduce the risk of disease recurrence, explained Reshma Jagsi, MD, DPhil, the Lawrence W. Davis professor and the chair of radiation oncology at the Emory University School of Medicine and a researcher at the Winship Cancer Institute of Emory University.

She added that, in recent studies, patients 65 years and older who opted out of adjuvant radiotherapy had a low risk of disease recurrence, suggesting that older patients may be able to safely skip radiotherapy after breast-conserving surgery. However, it remained unclear whether younger patients could safely opt out of adjuvant radiotherapy.

"Although techniques of radiation treatment have improved dramatically, and it is far more efficient and tolerable now than it used to be, patients appreciate having a choice about their treatments," Jagsi noted.

To determine if omitting radiotherapy would be feasible for younger postmenopausal patients with early-stage breast cancer, Jagsi and colleagues conducted the IDEA clinical trial, which enrolled patients between 50 and 69 years of age who had stage I HR-positive, HER2-negative breast cancer.

The Oncotype DX recurrence score was used to determine each patient's risk of recurrence based on the genetic profiles of their tumors. Patients with a low risk of recurrence were eligible to skip radiotherapy after breast-conserving surgery while still receiving standard-of-care adjuvant endocrine therapy for at least five years.

Two hundred patients enrolled in the study were eligible to skip radiotherapy (60 patients 50-59 years old and 140 patients 60–69 years old). Among 186 evaluable patients, 100% were alive five years after surgery, and 99% (184 patients) were breast cancer free at this time.

"These findings indicate that younger postmenopausal patients with stage I breast cancer who skip radiotherapy after breast-conserving surgery have a very low risk of disease recurrence within five years," said Jagsi. "However, five years is an early time point for this population, and longer-term follow-up of this study and others will be essential to determine whether this option can be safely offered to women in this age group.

"Studies like this one are important for identifying ways to improve the patient experience, both by identifying multiple treatment options to help patients regain a sense of control that a cancer diagnosis can seem to take away, and by ensuring that all patients are informed and empowered to make the decisions that are right for them," Jagsi said.

Limitations of the study include the short follow-up time and the small sample size.