When can radiation therapy be omitted in breast cancer treatment?

When to Omit Radiation Therapy in Breast Cancer Treatment

Radiation therapy can be safely omitted in women ≥70 years with early-stage, hormone receptor-positive breast cancer who meet specific criteria and will receive adjuvant endocrine therapy. 1

Patient Selection for Radiation Omission

Criteria for Safe Omission of Radiation Therapy

• Age ≥70 years 2, 1
• Tumor characteristics:
  • T1N0 (tumor size <2 cm, node-negative) 2, 1
  • Estrogen receptor-positive 2, 1
  • Clear surgical margins 2, 1
  • Grade 1 or 2 tumors 1, 3
• Treatment plan:
  • Patient has undergone breast-conserving surgery 2, 1
  • Patient will receive and adhere to 5 years of adjuvant endocrine therapy 2, 1

Emerging Evidence for Radiation Omission in Other Populations

Recent evidence suggests radiation might also be safely omitted in:

• Women ≥65 years with similar criteria as above 3
• Women ≥55 years with T1N0, grade 1-2, luminal A subtype breast cancer (defined by molecular testing with Ki67 ≤13.25%) 4

Expected Outcomes with Radiation Omission

Benefits

• Avoids radiation-related side effects 1
• Reduces treatment burden 1
• No impact on overall survival 2, 1, 3
• No impact on distant metastasis risk 1, 3

Risks

• Modest increase in local recurrence risk:
  • Approximately 8-10% at 10 years without RT vs. 2% with RT 1
  • PRIME II study: 4.1% without RT vs. 1.3% with RT at 5 years 1

When Radiation Therapy Should NOT Be Omitted

Radiation therapy remains strongly recommended for:

• Younger patients (<70 years) who don't meet specific criteria 2
• Patients with higher risk features:
  • Positive lymph nodes 2
  • Larger tumors (>2 cm) 2
  • Higher grade tumors 1, 3
  • Hormone receptor-negative disease 2, 1
  • Close or positive margins 2
• Patients who refuse or cannot tolerate endocrine therapy 2, 1
• Patients with DCIS (ductal carcinoma in situ) 5

Post-Mastectomy Radiation Therapy Indications

Radiation after mastectomy is indicated for:

• Patients with ≥4 positive axillary nodes (category 1 recommendation) 2
• Patients with T3-T4 tumors regardless of nodal status 2
• Consider for patients with 1-3 positive nodes, especially with additional risk factors 2

Clinical Implications and Pitfalls

Common Pitfalls

• Omitting radiation in patients who don't meet all criteria - This can lead to unacceptably high recurrence rates 6
• Poor adherence to endocrine therapy - Critical for the safety of omitting radiation 1
• Assuming DCIS can be treated without radiation - Studies show higher rates of salvage mastectomy when radiation is omitted for DCIS 5

Important Considerations

• Patient preference should be considered after thorough discussion of risks and benefits 1
• Regular follow-up with clinical exams and mammography is essential for patients who omit radiation 2
• The decision to omit radiation should be made in a multidisciplinary setting with radiation oncology input 1

The evidence clearly supports that carefully selected older patients with early-stage, hormone-positive breast cancer can safely omit radiation therapy without compromising overall survival, though with a small increase in local recurrence risk that must be discussed with the patient.