The New England Journal of MedicineOmitting Radiotherapy after Breast-Conserving Surgery in Luminal A Breast Cancer

Findings suggest a possible new perspective on luminal A breast cancer treatment.

The standard practice of prescribing adjuvant radiotherapy after breast-conserving surgery for luminal A breast cancer has been challenged by a recent prospective cohort study. The study aimed to assess the risk of local recurrence in women more than 55 years of age with specific tumor characteristics, without the use of radiotherapy. The findings may offer a new approach to treatment, potentially reducing costs and side effects associated with radiotherapy.

Study Design:

• Participants: Women at least 55 years old, with T1N0 (tumor size <2 cm and node negative), grade 1 or 2, luminal A–subtype breast cancer, receiving adjuvant endocrine therapy.
  • 740 registered patients, 500 eligible patients enrolled
• Methods: Prospective cohort study, omitting radiotherapy for patients with a Ki67 index of 13.25% or less.
• Primary Outcome: Local recurrence in the ipsilateral breast, with an acceptable risk boundary set at less than 5% at 5 years.

Key Findings:

• 5-year recurrence rate: 2.3% (90% CI, 1.3 to 3.8; 95% CI, 1.2 to 4.1), meeting the prespecified boundary.
• Contralateral breast cancer occurrence: 1.9% (90% CI, 1.1 to 3.2).
• Recurrence of any type: 2.7% (90% CI, 1.6 to 4.1).

Conclusion:

• Omitting radiotherapy in the specified patient group resulted in a low incidence of local recurrence at 5 years, suggesting a potential change in treatment approach for luminal A breast cancer.

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Did You Know?
Luminal A subtype breast cancer accounts for approximately 40% of all breast cancer cases, making this study’s findings potentially impactful for a significant portion of patients.