Timothy J Whelan, Sally Smith, Sameer Parpia, Anthony W Fyles, Anita Bane, Fei-Fei Liu, Eileen Rakovitch, Lynn Chang, Christiaan Stevens, Julie Bowen, Sawyna Provencher, Valerie Théberge, Anna Marie Mulligan, Zuzana Kos, Mohamed A Akra, K David Voduc, Tarek Hijal, Ian S Dayes, Gregory Pond, James R Wright, Torsten O Nielsen, Mark N Levine
BACKGROUND: Adjuvant radiotherapy is prescribed after breast-conserving surgery to reduce the risk of local recurrence. However, radiotherapy is inconvenient, costly, and associated with both short-term and long-term side effects. Clinicopathologic factors alone are of limited use in the identification of women at low risk for local recurrence in whom radiotherapy can be omitted. Molecularly defined intrinsic subtypes of breast cancer can provide additional prognostic information. METHODS: We performed a prospective cohort study involving women who were at least 55 years of age, had undergone breast-conserving surgery for T1N0 (tumor size <2 cm and node negative), grade 1 or 2, luminal A-subtype breast cancer (defined as estrogen receptor positivity of ≥1%, progesterone receptor positivity of >20%, negative human epidermal growth factor receptor 2, and Ki67 index of ≤13...
August 17, 2023: New England Journal of Medicine