Source / Disclosures
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Whelan TJ et al. Abstract LBA501. Presented at: ASCO Annual Meeting. 3-7 June 2022; Chicago.
Disclosures: Whelan reports research funding for his foundation from Exact Sciences. Please see the summary of all relevant financial disclosures for other researchers.
CHICAGO — Patients 55 or older with low-grade luminal A breast cancer who receive endocrine therapy can safely avoid radiation therapy after breast-conserving surgery, according to a prospective study presented at the ASCO annual meeting.
“We estimate that these findings could apply to up to 30,000 to 40,000 women per year who could avoid the morbidity, inconvenience, and cost of radiotherapy,” Timothy Joseph Whelan, MD, VascoAnd the Professor of Oncology and Canada Research Chair in Breast Cancer Research at McMaster University, said during a presentation.
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Background and styles
Whelan said that adjuvant radiotherapy is common after breast-conserving surgery and has been associated with a 67% reduction in the risk of local recurrence. However, daily treatments for up to 5 weeks can be inconvenient and expensive for patients, and can lead to significant acute and delayed toxicity, as well as rare, life-threatening adverse effects.
Given the lower risk of local recurrence and improved surgical techniques and systemic therapies, Whelan and colleagues sought to determine whether biomarker screening results could be used to identify patients with very low-risk disease for whom adjuvant radiotherapy could be omitted.
Timothy Joseph Whelan
The single-arm LUMINA Phase 3 study included 500 patients aged 55 years or older (mean age, 67 years; median tumor size, 1.1 cm) with node-negative breast cancer and luminal type A tumors, which were defined As ER of 1% or greater, PR greater than 20%, HER2 negative and Ki67 13.25% or less. The Ki67 protein has been associated with cancer cell proliferation.
The patients, collected between August 2013 and July 2017 from 26 centers across Canada, underwent breast-conserving surgery and received endocrine therapy for at least 5 years.
Local redundancy served as a primary outcome. Secondary outcomes included contralateral breast cancer, as well as recurrence, DFS and OS.
The median follow-up was 5 years.
Main results
The results showed 10 local recurrence events, all invasive, with a 5-year local recurrence rate of 2.3% (90% CI, 1.3-3.8). The researchers observed a similar 5-year rate for contralateral breast cancer (1.9%; 90% CI, 1.1-3.2; n = 8) and a rate of 2.7% (90% CI, 1.6-4.1) for any recurrence (n = 12). Whelan reported a 5-year DFS rate of 89.9% (90% CI, 87.5-92.2) and a 5-year OS rate of 97.2% (90% CI, 95.5-98.4). Only one patient died of breast cancer.
Ramifications
“Women 55 or older with T1N0, grade 1 to grade 2 luminal A breast cancer after breast-conserving surgery treated with endocrine therapy alone had a very low local recurrence rate at 5 years,” Whelan said. “The prospective and controlled nature of this multicenter study supports that these patients are candidates for radiotherapy to be omitted.”
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Deborah M Axelrod, MD
More than two thirds of breast cancers are luminal A cancers. They are ER positive, PR and HER2 negative and have low levels of Ki67 protein, reflecting cell growth. In this study, women had luminal A carcinomas with a Ki67 of 13%, which is considered to be on the lower side, and lymph nodes negative. They are the most favorable of the invasive cancers.
In the past decade, we have gained more knowledge about the behavior of breast cancers based on molecular sub-classification. The results of such studies have given us information about which cancers need more treatment and which cancers we can treat less. Improving this further, it is about reducing disease rates and improving quality of life without compromising oncological outcome.
The great strength of this study is that it is prospective and many centers have participated in it. It has been supported by other studies as well, and will identify patients with newly treated breast cancers for whom we can ignore radiation, which was the standard of care. These results also confirm the results of the PRIME II study.
The study has several limitations, including the fact that it was a single-arm, no-arm study compared to radiotherapy, and included older patients with smaller tumors. The local recurrence of ER-positive cancers continues to rise after 5 years, so long-term follow-up will be important. In addition, some older patients may prefer radiotherapy—particularly 1-week accelerated partial breast irradiation—to 5 years of endocrine therapy, which was commissioned in this study.
Omission of radiotherapy should be considered as an option for older women with localized breast cancer with favorable features who are receiving endocrine therapies. At New York University, our Department of Radiation Oncology participates in trials that divide breast cancer beyond its clinical and pathological features, such as the PRECISION trial, in which we use a genomic test called PAM50 (Prosgina, Veracyte) and the DEBRA trial, which uses the Oncotype DX assay (Exact Sciences ).
Deborah M Axelrod, MD
Perlmutter Cancer Center
New York University Langone Health
Disclosures: Axelrod does not report any relevant financial disclosures.
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Kamran Ahmed, MD
LUMINA is an important clinical trial that examined the role of radiotherapy omission in low-risk and early-stage breast cancer. I followed the results of PRIME II and CALGB 9343, looking specifically at patients with luminal A disease.
5-year data presented at ASCO showed a reduced risk of recurrence with adjuvant endocrine therapy alone. As we await further data maturation, it is important to note that not all patients with early-stage breast cancer are the same and that patients have an ad-hoc discussion with their radiation oncologist regarding the unique risk-benefit ratio in deciding their radiotherapy plan.
Kamran Ahmed, MD
Moffett Cancer Center
Disclosures: Ahmed did not report any relevant financial disclosures.
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