Source / Disclosures
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.
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.
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.
“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.”