FOR YEARS, the standard of care for many women with early-stage hormone receptor (HR)-positive breast cancer has included chemotherapy to shrink the tumor, followed by surgery and radiation.

A study presented at the San Antonio Breast Cancer Symposium in December 2023 and published Feb. 1, 2024, in the Journal of Clinical Oncology found some postmenopausal women ages 50 to 69 who had lumpectomy or other breast-conserving surgery for stage I HR-positive breast cancer and skipped radiation had low recurrence rates and 100% five-year survival. This study builds on previous research that found women 65 and older with this type of cancer can omit radiation—and its potential side effects—without impacting overall survival. Side effects of radiation can include fatigue, skin changes, and swelling at the radiation site or in the lymph nodes.

“This is important to study because, although techniques of radiation treatment have improved dramatically, patients appreciate having a choice about what treatments to receive,” says Reshma Jagsi, a radiation oncologist at the Emory Winship Cancer Institute in Atlanta and the study’s lead author.

The study, known as the IDEA trial, followed 186 women with stage I HR-positive, HER2-negative breast cancer. Participants had no cancer cells in the outer edge of tissue removed during surgery. They took the Oncotype DX 21-gene test, which indicated their cancers were unlikely to recur. All participants agreed to receive at least five years of endocrine therapy after surgery and did not receive radiation. After five years, all were alive, and all but two had not had a recurrence.

“Five years is an early time point for this population, and longer-term follow-up of this study and others will be absolutely essential to determine whether this option can be offered to younger women safely,” Jagsi says. “We must continue to follow these patients and those on other trials investigating similar approaches before the standard of care can change.”

Chirag Shah, a radiation oncologist at the Cleveland Clinic who was not involved with the IDEA study, agrees the results are promising but similarly cautions more follow-up is needed. “There are very few developments in breast radiation that are practice-changing with only five years of data,” he says. “We really want 10-year and 15-year follow-up data to show us that something is safe and effective.”

The IDEA study is part of recent research efforts to look at how to de-escalate, or de-intensify, cancer therapy to lessen potential side effects.

For Shah, treatment de-escalation is about learning what matters most to patients and then tailoring their treatment accordingly. “Studies like this give us a starting point to have good conversations with our patients about shared decision-making and how to achieve the lowest risk of recurrence with the lowest risk of side effects,” he says. He notes that previously published research shows women 65 and older who received breast-conserving surgery and endocrine therapy alone have a 10% risk of local recurrence at 10 years. “I have some women aged 65-plus who think a 10% risk of cancer recurrence at 10 years is good enough, and they choose to avoid radiotherapy. Others make the opposite choice.”

Given the improvements in radiation for breast cancer, Shah says he would like future studies to explore patient preference on radiation versus endocrine therapy. “There are many patients who would rather have five treatments of targeted radiation or partial breast irradiation in lieu of endocrine therapy,” he says. “We know that many patients end up not completing their course of endocrine therapy due to side effects, which can include hot flashes, joint pain and bone health issues. Even so, this study is a step in the right direction of treatment de-intensification.”