Biomarker Guidance May Allow Patients Aged 55 or Older With Low-Grade Luminal A–Type Breast Cancer to Avoid Radiation Therapy

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Based on guidance from biomarker screening, patients with low-grade luminal A–type breast cancer aged 55 and older may need endocrine therapy alone following breast-conserving surgery and may be able to avoid radiation therapy entirely, according to new research findings presented by Timothy Joseph Whelan, MD, FASCO, and colleagues at the 2022 ASCO Annual Meeting (Abstract LBA501).

In 2022, an estimated 287,850 new cases of invasive breast cancer are expected to be diagnosed in the United States. Luminal A is the most common subtype of breast cancer and represents 50% to 60% of all breast cancers diagnosed annually.

Timothy Joseph Whelan, MD, FASCO

Timothy Joseph Whelan, MD, FASCO

“Previous studies have shown that other tumor biomarkers can identify patients at very low risk of recurrence, thereby omitting chemotherapy as it is unlikely to offer benefit. The LUMINA [trial] results show that women with low levels of the Ki67 biomarker can avoid outcomes related to radiotherapy, including significant acute and late side effects; such effects include fatigue and rare life-threatening side effects of cardiac disease and second cancers,” said lead author Dr. Whelan, Professor in the Department of Oncology and Canada Research Chair in Breast Cancer Research at McMaster University, and a radiation oncologist at the Juravinski Cancer Centre in Hamilton, Ontario, Canada.

Low-grade breast cancer is usually slow-growing and less likely to spread than high-grade cancer. Localized breast cancer represents 63% of all breast cancer cases and has a 90% or higher 5-year survival rate. Regional breast cancer, which has spread to nearby lymph nodes, represents 29% of all breast cancer diagnoses and has a 75% to 85% 5-year survival rate.

Patients with a low-grade breast cancer diagnosis usually have the tumor surgically removed while maintaining the breast. Surgery is often followed by endocrine therapy to block or keep estrogen hormone levels low. Historically, these patients have undergone radiation therapy to reduce the risk of recurrence of the original tumor, but such therapy can be costly and may result in toxicity later in life. Also, with improved mammography and surgical techniques, as well as effective endocrine therapy, the risk of local recurrence following breast-conserving surgery has decreased in recent years.

A study that looked back at earlier cases of the disease found that women older than age 60 with low-grade luminal A–type breast cancer who underwent breast-conserving surgery alone had a low rate of local recurrence. Previous studies in women older than age 70 showed a risk of local recurrence of about 4% to 5%. The LUMINA findings suggest that in luminal A–type breast cancer, the risk is lower, even in women between the ages of 55 and 75.

About the Study

The single-arm prospective phase III LUMINA trial enrolled 500 patients from 26 centers in Canada who had a Ki67 tumor cell count of 13.25% or less. The patients had to be older than 55 and have node-negative, grade 1 or 2 tumors smaller than 2 cm that had been removed by breast-conserving surgery. Biopsy results had to show the cancers were luminal A–type tumors. Participants were followed for a median of 5 years. The median age of the participants was 67, and 88% of the patients were younger than age 75.

Enrollees had breast-conserving surgery for low-grade breast cancer, defined as the luminal A subtype, which is estrogen and progesterone receptor–positive and HER2-negative, and they had a low Ki67 cell count. Patients were not offered radiation therapy. They were followed every 6 months for the first 2 years and then yearly.

Key Findings

The 5-year rates in the study follow:

  • A 2.3% chance of local recurrence, the primary outcome
  • A 1.9% chance of breast cancer developing in the opposite breast
  • A recurrence-free survival rate of 97.3%
  • A disease-free survival rate of 89.9%
  • An overall survival rate of 97.2%.

The patients in the study will continue to be followed for up to 10 years for effects on long-term recurrence and survival.

ASCO Perspective

“This exciting data is very reassuring and could impact a large number of patients with cancer who have very low chances of their breast cancer returning even without radiation therapy. These findings are the first of a number of recent trials in breast cancer looking at reducing treatments that are still commonly used but that may not be necessary for appropriately selected patients,” said Corey Wayne Speers, MD, PhD, an ASCO expert in radiation oncology.

Disclosure: LUMINA was sponsored by the Canadian Breast Cancer Foundation and the Canadian Cancer Society. For full disclosures of the study authors, visit


The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.