In which patient population may sentinel lymph node biopsy (SLNB) be omitted?

Sentinel Lymph Node Biopsy May Be Omitted in Clinically Node-Negative Women Over 70 Years Old with Hormone Receptor-Positive, HER2-Negative Breast Cancer

The correct answer is A: Clinically node-negative women over 70 years old with hormone receptor-positive, HER2-negative breast cancer may safely omit sentinel lymph node biopsy (SLNB), particularly when they are committed to taking endocrine therapy. 1

Evidence-Based Rationale

Why Option A is Correct

The 2025 ASCO guideline update provides the strongest evidence supporting SLNB omission in this specific population 1:

• Women ≥70 years with cT1N0M0, ER-positive, HER2-negative breast cancer who will take endocrine therapy can safely omit both SLNB and radiation therapy 1
• The low incidence of nodal positivity (only 15.3% overall, and as low as 7.8% in grade 1, T1 tumors) coupled with low locoregional recurrence risk supports this de-escalation 2
• The Society of Surgical Oncology Choosing Wisely Campaign specifically recommends against routine SLNB in this population 1
• Five-year breast cancer-specific survival is excellent at 96% in this population, and survival is similar between SLNB-positive and SLNB-negative patients when they receive hormone therapy 3

Expanded Criteria from Recent Trials

The SOUND and INSEMA trials (2024) have further expanded omission criteria beyond just elderly patients 1, 4:

• SOUND trial: Patients with tumors ≤2 cm and negative preoperative axillary ultrasound showed equivalent 5-year distant disease-free survival with SLNB omission versus SLNB (locoregional relapse: 1.6% vs 1.7%) 1
• INSEMA trial: Patients with cN0, T1-T2 (≤5 cm) invasive breast cancer undergoing breast-conserving surgery demonstrated non-inferior 5-year invasive disease-free survival (91.9% without axillary surgery vs 91.7% with SLNB) 1
• Morbidity reduction: Omitting axillary surgery resulted in dramatically lower rates of arm/shoulder mobility restriction (2.0% vs 3.5%), lymphedema (1.8% vs 5.7%), and pain (2.0% vs 4.2%) 4, 5

Why Other Options are Incorrect

Option B (Premenopausal women with triple-negative disease): This population requires complete staging because:

• Triple-negative breast cancer has higher rates of nodal involvement and more aggressive biology 1
• Nodal status critically impacts decisions regarding adjuvant chemotherapy regimens 1
• These patients do not meet the low-risk criteria established by SOUND/INSEMA trials 1

Option C (Inflammatory breast cancer): SLNB is contraindicated, not simply omitted:

• These patients require upfront systemic therapy followed by complete axillary lymph node dissection 1
• Inflammatory breast cancer is clinically node-positive by definition (cN2-N3) 1

Option D (Biopsy-proven nodal metastasis): These patients need axillary dissection, not SLNB omission:

• Patients with proven nodal disease require either completion axillary lymph node dissection or targeted axillary dissection after neoadjuvant therapy 4
• SLNB is bypassed because the nodes are already known to be positive 4

Clinical Algorithm for SLNB Omission

Strict Criteria for Safe Omission (Based on ASCO 2025 Guidelines)

Primary criteria 1, 4:

• Age ≥70 years (or ≥50 years if meeting SOUND/INSEMA criteria)
• Tumor size ≤2 cm (cT1)
• Grade 1-2 disease
• Hormone receptor-positive
• HER2-negative
• Invasive ductal carcinoma
• Clinically node-negative (cN0)
• Negative preoperative axillary ultrasound
• Breast-conserving surgery planned
• Patient committed to endocrine therapy for at least 5 years 1

Critical Preoperative Requirement

Adjuvant therapy decisions MUST be discussed before surgery when omitting SLNB, since nodal status will remain unknown and cannot guide systemic therapy escalation 4:

• Confirm patient is not a candidate for abemaciclib (which requires ≥4 positive nodes or 1-3 positive nodes with high-risk features) 1
• Confirm patient is not a candidate for ribociclib based on primary tumor characteristics alone 1
• Document patient understanding that nodal status will be unknown 1

Common Pitfalls to Avoid

Pitfall 1: Overuse Despite Guidelines

Despite Choosing Wisely recommendations, more than 80% of eligible elderly patients still undergo SLNB in the United States 1, 6:

• Patient desire for "peace of mind" drives unnecessary procedures 1
• Physician anxiety about multidisciplinary care and potential criticism from colleagues 6
• Solution: Emphasize high likelihood of positive breast cancer-specific outcomes while maintaining quality of life 1

Pitfall 2: Ignoring Grade 3 Disease

In patients with pT1, grade 3, hormone receptor-positive cancers, SLNB may still be prudent due to higher likelihood of positive nodes, which would make them candidates for ribociclib if nodes are positive 1:

• Use nomograms to predict likelihood of positive SLN 1
• Engage in shared decision-making regarding value of SLNB in these cases 1

Pitfall 3: Applying Criteria Too Broadly

The omission criteria are specific and should not be extrapolated to 1, 4:

• Patients undergoing mastectomy (most trial data involved breast-conserving surgery)
• Patients with lobular histology (less data available)
• Patients unwilling or unable to take endocrine therapy 1

Quality of Life Considerations

The morbidity reduction from SLNB omission is substantial and directly impacts long-term quality of life 4, 5:

• Lymphedema reduction: 1.8% vs 5.7% (68% relative reduction) 4
• Mobility restriction reduction: 2.0% vs 3.5% (43% relative reduction) 4
• Pain reduction: 2.0% vs 4.2% (52% relative reduction) 4
• These complications have profound long-term impacts on daily functioning and should not be dismissed as secondary concerns 5