GRACE-trial: a Randomized Active-controlled Trial for vulvovaGinal atRophy in breAst Cancer Patients on Endocrine Therapy.

Inclusion Criteria: * breast cancer patient * current endocrine therapy (AI or SERM) * postmenopausal status, defined by: * 12 months amenorrhoea or * 6 months amenorrhoe and FSH level of \>40 mIU/mL or \*\>6 weeks after bilateral oophorectomy or * induced postmenopause (ovarian function suppression using GnRH-analogue) * presence of one or more symptoms of vulvovaginal atrophy (dyspareunia, dryness, irritation) Exclusion Criteria: * a history of vulvar or vaginal surgery (Inclusion is possible after hysterectomy. For these subjects no microbiome sampling will be performed. Microbiome analysis is not performed for these subjects.) * current other vulvar or vaginal disease * recent use of antibiotics/antifungals/corticosteroids (less than 1 month) * current use of vaginal hormonal treatment or vaginal moisturizer: inclusion is possible after a washout period of 4 weeks