What is the difference between Sentinel Lymph Node Biopsy (SLNB) and Axillary Lymph Node Dissection (ALND) in breast cancer treatment?

SLNB versus ALND in Early-Stage Breast Cancer

Sentinel lymph node biopsy (SLNB) has replaced routine axillary lymph node dissection (ALND) as the standard of care for axillary staging in early-stage breast cancer patients with clinically negative nodes, offering equivalent survival outcomes with significantly less morbidity. 1

Key Differences Between SLNB and ALND

Extent of Surgery

• SLNB removes only 1-3 lymph nodes (the first nodes draining the breast tumor) for pathologic examination 1
• ALND removes 10-20+ lymph nodes from levels I and II (sometimes III) of the axilla 1

Morbidity Profile

• SLNB results in an 11.5% reduction in postsurgical complications compared to ALND 1
• ALND causes significantly higher rates of lymphedema (13% vs 3%), axillary seroma, paresthesia, and nerve injury 1
• Infection rates are lower with SLNB alone 1

Diagnostic Accuracy

• SLNB has a false-negative rate of approximately 8-10% when performed by experienced surgeons using dual tracer technique (radioisotope plus blue dye) 1
• The negative predictive value of SLNB is 95-96% 1
• Successful mapping occurs in 97-98% of cases 1, 2

Current Evidence-Based Recommendations

When ALND Can Be Safely Omitted

Patients with Negative Sentinel Nodes:

• Completion ALND should NOT be performed in patients with negative sentinel nodes 1, 3
• 15-year follow-up data demonstrates no statistically significant differences in event-free survival (72.8% vs 72.9%) or overall survival (82.0% vs 78.8%) between SLNB alone and ALND 1, 4
• No axillary relapses occurred in the SLNB-only arm at 15-year follow-up 4

Patients with 1-2 Positive Sentinel Nodes Undergoing Breast-Conserving Surgery:

• ALND should NOT be recommended for women with early-stage breast cancer and 1-2 positive sentinel nodes who undergo breast-conserving surgery with whole-breast radiotherapy 1, 3
• This is based on strong evidence from the ACOSOG Z0011 trial showing no differences in overall survival or disease-free survival 1
• Lymphedema rates are significantly lower without ALND 1

Patients with 1-2 Positive Sentinel Nodes Undergoing Mastectomy:

• Post-mastectomy radiation with regional nodal irradiation (RNI) is recommended in place of completion ALND 1
• The 10-year axillary recurrence rate after RNI was 1.82% compared to 0.93% after ALND (HR 1.71, not statistically significant) 1
• No differences in overall survival (HR 1.17) or disease-free survival (HR 1.19) 1
• Lymphedema rates remain higher with ALND 1

When ALND Remains Indicated

Mandatory ALND scenarios:

• ≥3 positive sentinel nodes, followed by RNI radiation therapy 1, 3
• Failed or technically unsatisfactory SLNB procedure 1, 3
• Clinically suspicious or palpable axillary nodes after sentinel node removal 1, 3
• Inflammatory breast cancer or N2/N3 stage disease 3

Traditional approach (though increasingly questioned):

• Positive sentinel nodes detected by routine histopathologic examination traditionally prompted completion ALND 1
• However, 40-70% of patients with a positive sentinel node have no additional positive nodes on completion ALND 5

Technical Considerations

Optimal SLNB Technique

• Dual tracer method (both radioisotope and blue dye) reduces false-negative rates from 9.9% to 7.0% 1
• Removal of at least 3 sentinel nodes when possible improves accuracy 6
• Successful mapping rates >90% are associated with lower false-negative rates (6.3% vs 11.1%) 1

Pathologic Evaluation

• Routine hematoxylin and eosin staining is standard 1
• Immunohistochemistry can detect micrometastases in an additional 10% of cases, but clinical significance remains uncertain 1
• Isolated tumor cells detected only by specialized techniques do not currently mandate ALND 1

Common Pitfalls and Caveats

Critical warning: About half of patients with false-negative SLNB have clinically suspicious nodes palpable at surgery, as gross tumor involvement interferes with tracer uptake and lymph flow 1. Surgeons should maintain a low threshold for defaulting to ALND when nodes appear clinically suspicious.

Surgeon experience matters: SLNB should only be performed by surgeons with demonstrated low false-negative rates and high successful mapping rates 3. Studies with >100 patients show significantly lower false-negative rates (6.7% vs 9.0%) 1.

Special populations: SLNB can be performed in select circumstances including clinically node-negative patients with cT3-T4c tumors, multicentric tumors, DCIS treated with mastectomy, obese patients, male patients, pregnant patients, or those with prior breast/axillary surgery 3.

Highly select low-risk patients: SLNB may be omitted entirely in postmenopausal women ≥50 years with negative preoperative axillary ultrasound, grade 1-2, small (≤2 cm), hormone receptor-positive, HER2-negative breast cancer undergoing breast-conserving therapy 3.