Brachytherapy Alone for FIGO Stage IIB Endometrial Carcinoma
Brachytherapy alone can be considered for highly selected stage IIB patients with low-grade (Grade 1-2) endometrioid histology, no or minimal lymphovascular space invasion (LVSI), and who have undergone complete pelvic lymph node dissection with negative nodes (pN0), but external beam radiotherapy remains the standard recommendation for most stage IIB cases.
Risk Stratification Determines Treatment
The 2025 ESGO-ESTRO-ESP guidelines classify stage IIB endometrial cancer into different risk categories based on molecular classification and histopathologic features 1:
High-Intermediate Risk (Most Stage IIB Cases)
- Stage IIBm MMRd or NSMP low-grade with ER-positive disease falls into the high-intermediate risk category
- External beam radiotherapy is recommended for optimal pelvic control 1
- Vaginal brachytherapy alone is an alternative option specifically for patients who underwent lymph node staging and are pN0 1
When Brachytherapy Alone May Be Acceptable
The evidence supports brachytherapy alone only in a narrow subset:
Required criteria:
- Grade 1-2 endometrioid histology
- Microscopic (not macroscopic) cervical stromal invasion
- Complete pelvic lymphadenectomy performed with negative nodes
- No substantial LVSI
- Preferably younger age (<60 years)
Supporting evidence: A multi-institutional analysis of 106 stage II patients treated with vaginal brachytherapy alone showed excellent outcomes with 5-year vaginal failure of only 2.6%, pelvic nodal failure of 4.2%, and overall survival of 76.2% 2. However, 98.1% had microscopic (not macroscopic) cervical invasion, 88.6% had Grade 1-2 disease, and 89.6% underwent pelvic lymphadenectomy—highlighting the highly selected nature of this cohort.
Molecular Classification Changes Everything
The 2025 guidelines introduce molecular-based staging that can dramatically alter treatment:
- POLEmut stage IIB: Classified as LOW RISK—no adjuvant therapy recommended 1
- p53abn or high-grade/ER-negative stage IIB: Classified as HIGH RISK—requires external beam radiotherapy plus chemotherapy 1
Clinical Algorithm
Step 1: Obtain molecular classification (POLEmut, MMRd, NSMP, p53abn)
Step 2: If POLEmut → No adjuvant therapy needed
Step 3: If p53abn or high-grade → External beam RT + chemotherapy required
Step 4: If MMRd or NSMP low-grade:
- Complete lymph node dissection performed AND pN0 AND Grade 1-2 AND microscopic cervical invasion only → Consider brachytherapy alone
- Otherwise → External beam radiotherapy recommended
Critical Pitfalls to Avoid
Do not use brachytherapy alone for macroscopic cervical stromal invasion—only 1.9% of successfully treated patients in the research had macroscopic disease 2
Do not skip lymph node assessment—lack of pelvic node resection was a significant hazard for progression on multivariable analysis 2
Age matters—patients ≥60 years had significantly worse outcomes with brachytherapy alone 3
Substantial LVSI is a contraindication—this upstages patients and requires external beam RT 1
The Evidence Hierarchy
The 2025 ESGO-ESTRO-ESP guidelines 1 represent the highest quality, most recent evidence and clearly state that external beam radiotherapy is the standard for high-intermediate risk stage IIB disease, with brachytherapy alone reserved as an alternative for the pN0 subset. Older 2013 ESMO guidelines 4 suggested brachytherapy alone only for Grade 1-2 tumors with <50% myometrial invasion, negative LVSI, and complete surgical staging—criteria that align with current recommendations but are less molecularly refined.
The research data 2, 5, 3, 6 consistently shows that brachytherapy alone achieves excellent local control (>95% at 5 years) but only in highly selected patients meeting the strict criteria outlined above. Distant metastasis, not local failure, becomes the primary pattern of recurrence in these cases 5.