Rethinking Sentinel Lymph Node Biopsy in Early Breast Cancer: SOUND & INSEMA Trials

Evolution of Axillary Management

• 🏥 Historically, breast cancer surgery involved aggressive radical mastectomies and axillary lymph node dissections (ALD) due to the understanding of cancer spread by direct extension.
• 💡 Over time, the understanding shifted to cancer spreading via blood and lymph, leading to de-escalation strategies starting with sentinel lymph node biopsy (SLNB) for clinically node-negative women.
• 📉 Landmark trials like NSABP32 demonstrated SLNB equivalence to ALD, and the Akazogi III study showed safety in omitting completion ALD for low-volume axillary disease.
• 👵 Studies in women over 70 also indicated that omitting axillary staging entirely is safe and improves quality of life.

Sentinel Lymph Node Biopsy: Pros and Cons

• ✅ Benefits of Omission: Reduced surgical morbidity, lower risk of lymphedema (2-5%), decreased wound infections, improved shoulder function, shorter recovery, potential avoidance of general anesthesia, and lower healthcare costs.
• ⚠️ Risks of Omission: Loss of crucial nodal staging information, potentially missing positive nodes in ~15% of cases, which can impact adjuvant therapy decisions, prognosis, and eligibility for clinical trials.
• 🤝 Shared decision-making is paramount, as axillary staging impacts radiation and systemic therapy decisions, and patient preferences vary.

SOUND and INSEMA Trial Findings

• 🔬 The SOUND trial randomized over 400 women with small (<2cm), clinically node-negative breast cancers (primarily ER+, HER2-) to SLNB vs. no axillary surgery. It found identical distant disease-free survival (97.7% vs. 98%) and no difference in overall survival or recurrence.
• 📊 The INSEMA trial, with over 5,500 patients, also randomized clinically node-negative patients to SLNB vs. omission. It reported no difference in 5-year disease-free survival (92% in both groups) and confirmed fewer complications with omission.
• 🎯 Both trials predominantly enrolled older, post-menopausal patients with hormone receptor-positive, HER2-negative, smaller tumors, suggesting these are the select populations where omission is being studied.

Patient Selection and Adjuvant Therapy Implications

• 🎯 Patients who should still receive nodal staging include premenopausal patients with ER+/HER2- cancer, and all patients with HER2+ or triple-negative breast cancer, as nodal status strongly impacts adjuvant therapy decisions.
• 📈 Low-risk patients for nodal metastases include those with low-grade tumors, no lymphovascular invasion, and potentially older age.
• ⚠️ Higher-risk patients for nodal positivity include those with high Ki-67, larger tumor sizes, lymphovascular invasion, and younger age.
• 💊 Omission of SLNB can affect eligibility for newer agents like CDK46 inhibitors, which are often indicated for high-risk ER+/HER2- disease, and nodal status can be a criterion for their use.
• 💡 Genomic profiling (e.g., Oncotype DX) is increasingly driving chemotherapy decisions, especially in post-menopausal women, potentially diminishing the role of nodal staging for this specific aspect.

Integrating New Evidence into Practice

• 🏥 Institutions are developing multidisciplinary consensus criteria for SLNB omission, often focusing on post-menopausal women with specific low-risk tumor characteristics (e.g., small, low-grade, ER+/HER2-).
• 🗺️ Routine pre-operative axillary imaging (ultrasound) is becoming standard to identify eligible patients.
• 🚧 Barriers to adoption include integrating SLNB omission with radiation planning (e.g., eligibility for partial breast radiation) and the need for continued education and provider comfort.
• 🚀 Future research aims to fine-tune patient selection, potentially re-evaluating the necessity of negative axillary ultrasound, and harmonize trial eligibility to allow broader access to de-escalated therapies.