medwireNews: Combining clinicopathologic factors with the luminal A subtype could help identify women with a very low risk for breast cancer local recurrence after breast-conserving surgery, making them good candidates for adjuvant radiotherapy omission, suggests the LUMINA study.
“Over 300,000 women are diagnosed yearly with invasive breast cancer in North America,” and “we estimate that these results could apply to as many as 30,00 to 40,000 women per year who could avoid the morbidity, inconvenience, and cost of radiotherapy,” commented study author Timothy Whelan (McMaster University, Hamilton, Ontario, Canada) at the 2022 ASCO Annual Meeting, held in Chicago, Illinois, USA.
Outlining the rationale for the study, he explained that clinicopathologic parameters alone, such as age and tumor size, “have been limited in their ability to identify very low-risk patients who could be spared radiotherapy.”
The researchers therefore sought to assess whether molecularly defined intrinsic subtypes, which are known to be prognostic for recurrence, could provide additional information to guide decision making in this setting.
They screened women aged 55 years or older on adjuvant endocrine therapy after breast-conserving surgery for clinical stage T1N0, grade 1–2 invasive ductal disease. Participants were required to have at least 1% estrogen receptor-positive cells and at least 20% progesterone receptor-positive cells on immunohistochemical analysis, as well as be negative for HER2.
Following central Ki67 testing, patients with Ki67 levels no greater than 13.25% – that is, those confirmed to have luminal A disease – were enrolled in the study and not given radiotherapy, while those with higher Ki67 levels received radiotherapy off study.
Among the 500 enrolled patients, there were 10 cases of local recurrence – all invasive – in the first 5 years, giving a cumulative rate of 2.3%. The upper limit of the 90% confidence interval was 3.8%, which is “well below” the prespecified boundary of 5.0%, noted Whelan.
There were eight cases of contralateral breast cancer in the cohort and 12 cases of any recurrence, equating to respective cumulative 5-year rates of 1.9% and 2.7%.
And the disease-free survival and overall survival rates at the 5-year mark were 89.9% and 97.2%, respectively.
“The prospective and controlled nature of this multicenter study supports” that patients with low-risk clinicopathologic factors and luminal A disease “are candidates for omission of radiotherapy,” summarized the presenter.
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2022 ASCO Annual Meeting; Chicago, Illinois, USA: 3–7 June
Abstract link https://meetings.asco.org/abstracts-presentations/208258
Author: Shreeya Nanda