Abstract Background: 74% of women have urogenital symptoms classified as Genito-urinary Syndrome of menopause (GSM) during breast cancer treatment. Promestriene is effective and safe in the treatment of GSM. However, some women and oncologists are not comfortable with long-term use. Therefore, new options for and alleviating GSM have been considered, such as microablative fractional CO2 laser (CO2L) and microablative fractional radiofrequency (RF). Objective: To compare the effect of promestriene, CO2L, and RF treatments of GSM in women with breast cancer in the use of antiestrogens therapy, concerning clinical and histological findings of vulvar vestibule. Methods: This is a secondary analysis of a Multi-arm randomized controlled trial (NCT04081805). Were eligible for the study 100 women with breast cancer using adjuvant endocrine therapy referring moderate to severe symptoms of GSM (itching, dyspareunia, fissures, thinning of vaginal rugae, and tropism reduction). After providing written informed consent, they were evaluated according to pre and post-treatmentpost-treatment protocol by filling the VAS of GSM and by clinical evaluation including a standardized gynecological exam with vestibular biopsy. Women were then randomized to either CO2L, RF or promestriene groups. The CO2L and RF groups received 3 consecutive monthly outpatient vulvovaginal energy applications. The CT was oriented for domiciliary use of promestriene, 1g/d for 21 days and, subsequently, twi4 month seek for 4 months. The follow-up visit was performed 120 days after interventions and also included an evaluation of global patient impression of improvement (5 points Likert scale). Results: 94 women were randomized as follows: 32 in the CO2L group, 32 in the RF and 30 in the promestriene. 70 patients concluded the treatment and had adequate pre and post-treatment material to analyze, 23 CO2L, 21 RF and 26 promestriene. Pre-treatment demographic and clinical data are presented on table 1. The evolution of GSM according to each treatment is demonstrated on table 2. Was also reported a high satisfaction after the treatment protocol in all groups evaluated by Likert Scale:CO2L 4,783 (0,518), RF 4,150 (0,813), CT 4,280 (1.13), p=0,055. The histological parameters were presented on table 3. Histological atrophy was surprisingly identified in only 4 women (5.7%), pre-treatment. No injuries to the histological structure of the vulvar vestibule or relevant clinical adverse events were identified post-treatments. Conclusion: CO2L, RF, and promestriene provided significant and similar improvement of GSM in women with breast cancer using anti-estrogens. The use of energies did not cause structural tissue damage or relevant clinical complications. Table 1. Clinical and demographic parameters before treatment Mean (standard deviation); BMI body mass index, Tukey test: Similar letters (a, b) mean similar results. Chi-Square Table 2. Evolution of GSM (VAS) after treatment with CO2L, RF, and promestriene Mixed ANOVA. VAS - Visual Analog Scale of GSM Symptoms, values expressed in mean (SD) Table 3. Histological parameters according groups and pre and post-treatment Citation Format: Angela Flavia L. Waitzberg, Andreia Fabiana V. Franco, Ana Maria Bianchi-Ferraro, Roberto Marcela, Gabriela Cantarelli, Chayane Dedonatto, Marisa Patriarca, Rita Dardes, Neila Speck, Zsuzsanna Jarmy-di Bella, Marair Sartotti, Joaquim Almeida. CO2 laser, radiofrequency, and promestriene in treatment of genitourinary syndrome of menopause in breast cancer survivors. Clinical and histological aspects of a randomized control trial [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P4-07-34.