Vaginal Laser Therapy for Genitourinary Syndrome of Menopause in Breast Cancer Survivors: A Modality-Specific Systematic Review of Efficacy, Durability, and Safety

Background: Genitourinary syndrome of menopause (GSM) is common among breast cancer survivors, particularly during endocrine therapy, and vaginal laser therapy has been proposed as a nonhormonal option; CO2 and Er:YAG devices differ technically and their effects should not be assumed equivalent. Objective: To assess the efficacy, durability, and safety of vaginal laser therapy for GSM in breast cancer survivors, treating CO2 and Er:YAG separately. Methods: Five databases and trial registries were searched from inception to 22 August 2026. Risk of bias was assessed with RoB 2, ROBINS-I, and the JBI cohort checklist; certainty with GRADE; and findings were synthesized narratively because of heterogeneity. Results: Thirty-five evidence reports represented 28 study families (19 CO2, six Er:YAG alone, one Er:YAG plus Nd:YAG versus Er:YAG, two other systems). Only two CO2 trials used sham controls, and neither showed a reproducible laser-specific benefit for dyspareunia or overall sexual function; one favored CO2 for daily dryness and selected objective measures but not intercourse dryness or dyspareunia. Active-comparator trials showed no consistent laser advantage, and uncontrolled cohorts reported short-term gains that attenuated with follow-up. No serious treatment-related adverse event was reported in the included studies; however, the evidence was insufficient to assess uncommon or delayed harms. Certainty was low to very low for sham-controlled CO2 effects and very low for Er:YAG versus hyaluronic acid; no study compared the modalities directly. Conclusions: Available evidence does not establish a consistent laser-specific benefit on the main patient-reported outcomes. CO2 has the larger evidence base, but this does not demonstrate greater efficacy; Er:YAG data rely mainly on active-comparator or uncontrolled studies. No direct CO2-versus-Er:YAG comparison is available, and neither modality superiority nor equivalence can be inferred. Durability and safety beyond the short term remain uncertain.