Endocrine therapy after breast-conserving surgery may be the only treatment needed in patients aged ≥55 years with low-grade luminal type-A breast cancer, sparing them radiation therapy, including its side effects, financial burden, and inconvenience, according to the single-arm LUMINA clinical trial reported at the 2022 ASCO meeting. Low levels of Ki67, a marker of cancer-cell proliferation, was a criterion for enrollment. According to several speakers at the meeting, these results highlight the importance of biomarker screening in patients with breast cancer.
All 501 patients enrolled in the study had surgery followed by 5 years of endocrine therapy. Radiation therapy was omitted. The results showed that the outcomes in these patients were similar to historical patients observed after radiation therapy.
At 5 years, the rate of local recurrence was 2.3% (the primary end point); the rate of contralateral breast cancer was 1.9%; the recurrence-free survival was 97.3%; the disease-free survival was 89.9%; and the overall survival was 97.2%. In all, 1 of 13 deaths resulted from breast cancer.
“Previous studies have…suggested that radiation can be omitted for older women age 65 or older with low-grade breast cancer. The LUMINA results show that women with luminal type-A breast cancer and low levels of the Ki67 biomarker can avoid outcomes related to radiotherapy, including significant acute and late effects, such as fatigue and rare life-threatening side effects of cardiac disease and second cancers,” said lead investigator Timothy Joseph Whelan, MD, FASCO, Canada Research Chair in Breast Cancer Research, McMaster University, and Radiation Oncologist, Juravinski Cancer Centre, Hamilton, Ontario, Canada.
“These results could apply to 30,000 to 40,000 women in North America. The findings indicate that there is a significant subset of patients with breast cancer—not just older women—who can avoid radiation therapy. This could be practice-changing,” Dr Whelan emphasized.
Luminal A subtype is associated with the lowest risk for recurrence among the 4 subtypes of breast cancer. Luminal A is hormone receptor–positive, HER2-negative breast cancer with low levels of Ki67. Patients with this subtype are treated with breast-conserving surgery, followed by endocrine therapy, and many patients undergo radiation to reduce the risk for local recurrence. However, radiation therapy is associated with acute and late adverse events, as well as increased costs and the inconvenience of coming to the clinic daily for as long as 5 weeks.
Studies have suggested that in women aged >60 years who receive only breast-conserving surgery, the rate of local recurrence is approximately 4% to 5%. The LUMINA study evaluated women aged ≥55 years.
Follow-up will continue for 10 years to determine the effects of treatment on long-term recurrence and survival.
Commenting on the study, Corey Speers, MD, PhD, Assistant Professor of Radiation Oncology, University of Michigan Rogel Cancer Center, Ann Arbor, said, “Congratulations on this very important trial. We have known for a long time from prospective early-stage trials that many women with luminal A subtype are cured with surgery or radiation therapy alone. Historically, we have tried to identify variables such as stage, grade, and size of surgical margins, that are associated with better outcomes, and indeed, we can find some patients who would do well without radiation, but this study is the first molecularly stratified test to evaluate whether we can add intrinsic molecular subtype to clinical pathologic factors to identify women who can safely avoid radiation.”
“A local recurrence rate of less than 5%, really 2.3% at 5 years, is reassuring,” Dr Speers said.