Clinical outcomes following brachytherapy for endometrial cancer patients with narrow vaginal anatomy.

Abstract

Background: Adjuvant high-dose-rate (HDR) vaginal brachytherapy (VBT) for endometrial cancer (EC) is delivered with vaginal cylinders ranging from 2.0 to 4.0 cm in diameter. Dose heterogeneities as high as 170-210% can be observed with the narrowest 2.0 cm cylinders potentially increasing the risk of vaginal scarring. Therefore, use of larger diameter cylinders is favored when clinically feasible. Nonetheless, certain clinical scenarios necessitate the use of narrow cylinders despite their unfavorable dosimetry. This study reports the clinical outcomes of EC patients treated with 2.0 cm diameter cylinders at a single institution.

Methods: From an IRB-approved database of 770 EC patients treated with VBT (11/2015-07/2024), 45 (5.8%) treated with 2.0 cm diameter cylinders were retrospectively reviewed. All received 10 Gy x 3 fractions prescribed to the cylinder surface, to mitigate high surface doses. Patient demographics, recurrence rates, and toxicities were analyzed. Toxicities were assessed using CTCAE v4.0, and freedom from vaginal recurrence was determined by Kaplan-Meier analysis.

Results: The median age was 69 years, and 80% were nulliparous. Most had stage I-II disease (82%), and the most common histology was endometrioid (69%). The 2-year freedom from vaginal recurrence was 97% with only 1 in-field recurrence. No grade ≥2 gastrointestinal or urinary toxicities were observed. Freedom from grade ≥2 vaginal stenosis was 85%.

Conclusion: Use of the 2.0 cm diameter cylinder was rare and used in <6% of EC patients treated with VBT. The regimen of 10 Gy x 3 fractions to the cylinder surface was well-tolerated and achieved excellent local control.