What is the role of Sentinel Lymph Node Dissection (SLND) in the management of uterine, cervical, and vulval cancer?

Role of Sentinel Lymph Node Dissection (SLND) in Uterine, Cervical, and Vulval Cancer

Sentinel lymph node dissection (SLND) is an effective alternative to complete lymphadenectomy in selected patients with uterine, cervical, and vulval cancer, providing important prognostic information while reducing morbidity compared to traditional lymphadenectomy. The application of SLND varies by cancer type and stage, with specific technical considerations for each anatomical site.

Cervical Cancer

Indications

• SLND should be considered in FIGO stage I cervical cancer 1
• Most appropriate for tumors <4 cm, with highest detection rates in tumors <2 cm 1
• Can be performed prior to radical hysterectomy or fertility-sparing trachelectomy

Technique

• Tracer is injected directly into the cervix using:
  • Blue dye (Isosulfan Blue 1%)
  • Technetium-99m radiocolloid
  • Fluorescent indocyanine green (ICG) - increasingly preferred 2
• Sentinel nodes should be detected bilaterally 1
• SLND should be performed before tumor excision to preserve lymphatic mapping 3

Clinical Significance

• Provides important staging information with less morbidity than complete lymphadenectomy
• High sensitivity (92%) for detecting nodal metastases 3
• May allow for custom-designed treatment strategies based on nodal status

Endometrial Cancer

Indications

• SLND can be considered for surgical staging of apparent uterine-confined malignancy 1
• Appropriate when there is no metastasis on imaging and no obvious extrauterine disease at exploration 1
• Particularly valuable in low to intermediate-risk patients 1

Technique

• Cervical injection with:
  • Superficial (1-3 mm) and deep (1-2 cm) injections 1
  • Delivers dye to main lymphatic channels in cervix and corpus
  • ICG with near-infrared camera provides high detection rates 1
• Common SLN locations:
  • Medial to external iliac
  • Ventral to hypogastric
  • Superior part of obturator region
  • Less commonly in common iliac presacral region 1

Clinical Significance

• SLND is still considered experimental but large series suggest feasibility 1
• Increases detection of micrometastases through ultrastaging 1
• Implementation of SLND can reduce the number of radical lymph node dissections by nearly half 4
• SLN mapping should be performed before hysterectomy 1

Vulval Cancer

Indications

• SLND is an alternative standard-of-care approach to lymphadenectomy in select women with squamous cell carcinoma 1
• Candidates include:
  • Patients with negative clinical groin examination and imaging
  • Primary unifocal vulvar tumor <4 cm
  • No previous vulvar surgery that may have impacted lymphatic flow 1

Technique

• Increased sensitivity when both radiocolloid and dye are used:
  • Technetium-99m sulfur colloid (injected 2-4 hours before procedure)
  • Isosulfan Blue 1% (3-4 cc injected peri-tumorally using four-point technique)
• SLN procedure should be performed before vulvar tumor excision 1
• Gamma probe used to detect radiocolloid before making groin incision 1, 5

Clinical Significance

• Significantly reduces postoperative morbidity:
  • Traditional inguinofemoral lymphadenectomy: 20-40% wound complications, 30-70% lymphedema risk 1
  • SLND: decreased complications without compromising detection of metastases
• Complete inguinofemoral lymphadenectomy recommended if ipsilateral SLN is not detected 1
• High reliability in identifying nodal metastases in early vulvar cancer 5

Important Considerations

1. Technical expertise: SLND should be performed by high-volume surgeons with appropriate training 1

2. Detection methods:

   • Combined techniques (radiocolloid + dye) improve detection rates
   • ICG with near-infrared imaging is increasingly preferred due to:
     • Low toxicity
     • Confinement to vascular compartment
     • Rapid excretion
     • Rare allergic reactions (compared to blue dye) 2

3. Limitations and cautions:

   • For endometrial cancer: evidence still evolving, though increasingly accepted 1
   • For cervical cancer: most reliable in early-stage disease with smaller tumors 1
   • For vulvar cancer: established as standard of care for appropriate candidates 1

4. Management of positive SLNs:

   • May require complete lymphadenectomy and/or adjuvant radiation 1
   • In cervical cancer, treatment may be altered in approximately 26% of patients based on SLN findings 3

SLND represents an important advancement in gynecologic oncology, allowing for more precise staging with reduced morbidity when performed in appropriate patients by experienced surgeons.