Vaginal Brachytherapy Boost Following EBRT in Endometrial Carcinoma
A vaginal brachytherapy boost after EBRT should NOT be routinely used in endometrial cancer, as it provides no clear benefit for vaginal control (approximately 2% vaginal recurrence at 5 years with either modality alone) while significantly increasing gastrointestinal toxicity. 1
When to AVOID Vaginal Brachytherapy Boost
The American College of Radiology and other guideline societies explicitly recommend against routine use of vaginal brachytherapy boost after EBRT because:
- Vaginal control rates are excellent with EBRT alone, with 5-year vaginal recurrence rates of approximately 2% 1, 2
- Adding VBT to EBRT significantly increases acute grade 1-2 gastrointestinal toxicity (53.8% with EBRT alone vs higher rates with combination) without improving local control 1, 2
- A retrospective study of 157 patients showed no difference in local failure between those receiving VBT boost (6.0%) versus those who did not (7.7%), but rectal bleeding/proctitis was significantly higher with the boost (18.6% vs 3.8%, p=0.01) 3
- Survival outcomes show no significant difference between EBRT alone and EBRT + VBT in stage I-II high-risk disease 4
The ONLY Clear Indication for VBT Boost After EBRT
The American Society for Radiation Oncology recommends considering vaginal brachytherapy boost after EBRT ONLY when there are positive vaginal surgical margins, as this is the only clear indication supported by evidence 1.
Additional Scenarios Where VBT Boost MAY Be Considered
While evidence is limited, a VBT boost after EBRT may be appropriate in highly selected cases:
- Stage II disease with cervical stromal involvement and close margins - An increased risk of vaginal recurrence may warrant brachytherapy boost, though no high-quality randomized evidence supports this practice 5
- Stage III disease with close or positive margins - Given the low added toxicity, a boost may be appropriate in patients at highest risk for vaginal cuff failure 5
- Select high-risk features including high grade, extensive invasion, and use of lower EBRT doses may be considered, though evidence is retrospective 6
Dosing When VBT Boost Is Used
If a vaginal brachytherapy boost is given after EBRT, the National Comprehensive Cancer Network recommends:
- 4-6 Gy × 2-3 fractions prescribed to the vaginal mucosa 7
- 5-6 Gy × 2 fractions to the vaginal mucosa 7
- Target should be limited to the upper vagina only 7
Treatment for Isolated Vaginal Relapse (Different Scenario)
For patients who develop isolated vaginal relapse after surgery WITHOUT prior adjuvant radiation:
- Combined EBRT and brachytherapy is recommended, achieving 89% complete remission rate with 77% remaining disease-free at median 44 months follow-up 5, 1
- This represents salvage treatment, not adjuvant boost therapy 5
Common Pitfalls to Avoid
- Do not routinely add VBT boost to EBRT - This increases toxicity without improving outcomes in most patients 1, 3
- Do not confuse adjuvant boost with salvage treatment - The evidence supporting combined EBRT + VBT applies to recurrent disease in previously unirradiated patients, not as routine adjuvant boost 5
- Do not neglect vaginal stenosis prevention - When VBT is used, counsel patients on vaginal dilators starting 2-4 weeks after treatment completion 7