Which group of lymph nodes are targeted in radiotherapy for endometrial cancer?

Lymph Node Groups Targeted in Endometrial Cancer Radiotherapy

Pelvic radiotherapy for endometrial cancer should target the lower common iliacs, external iliacs, internal iliacs, parametrium, upper vagina, and presacral lymph nodes (in patients with cervical involvement). 1

Standard Pelvic Radiation Fields

• Pelvic radiotherapy targets the following lymph node groups:
  • Lower common iliac nodes 1
  • External iliac nodes 1
  • Internal iliac nodes 1
  • Parametrial tissue 1
  • Presacral lymph nodes (especially in patients with cervical involvement) 1
  • Upper vagina 1

Extended-Field Radiotherapy

• Extended-field radiotherapy includes the standard pelvic volume plus:
  • Entire common iliac chain 1
  • Para-aortic lymph node region 1
  • The upper border should extend at least to the level of the renal vessels 1

Dosing and Technical Considerations

• External-beam doses for microscopic disease should be 45-50 Gy 1
• Multiple conformal fields based on CT-treatment planning should be used 1
• For vaginal brachytherapy after hysterectomy, the target should be limited to the upper vagina 1

Rationale for Nodal Coverage

• The obturator and internal iliac nodes are the most frequent sites of lymph node metastasis in endometrial cancer 2
• The lymph node spread pathway in endometrial cancer consists of:
  • Major route via the obturator node or internal iliac node with or without parametrial involvement 2
  • Less commonly, a direct para-aortic pathway 2

Special Considerations

• Circumflex iliac nodes distal to the external iliac nodes (CINDEIN) have a low risk of metastasis (2.8%) in intermediate and high-risk endometrial cancer 3
• Removal of CINDEIN can potentially be eliminated in patients with G1 endometrial cancer and patients with G2 endometrial cancer who have no pelvic node metastasis 3
• The 2021 NRG Oncology/RTOG Consensus Guidelines recommend including the para-aortic and inferior obturator nodal regions in the clinical target volume 4

Historical Context

• The earliest intracavitary radium treatment for uterine cancer was reported in 1908 5
• In the 1950s and 1960s, external beam radiation was introduced to eradicate cancer in regional lymphatic vessels, particularly for Stage II and III disease 5
• Modern radiation techniques now allow for more precise targeting of lymph node groups based on patterns of spread and risk stratification 5