Supplementary Material for: Vulvar metastasis from breast cancer treated with abemaciclib plus fulvestrant: a case report

Abstract

Introduction
Breast cancer is the most common malignant tumor in women, affecting approximately 1 in 9
women worldwide. In contrast, vulvar cancer remains rare, accounting for <1% of all cancers among women. Metastatic vulvar tumors are even rarer, constituting only 5 to 8% of all vulvar cancers. In some cases, breast cancer may metastasize to the vulva or vulvar tumors can arise from ectopic breast tissue.

Case Report
We report the case of a 78-year-old woman with vulvar metastasis of breast origin occurring 17 years after the diagnosis of primary breast cancer. The recurrence was identified by a PET scan concurrent with the patient reporting episodes of vaginal bleeding. Diagnosis was confirmed by clinical examination and biopsy. The proposed treatment was combined cyclin-dependent kinases 4 and 6 (CDK4/6) inhibitor abemaciclib and anti-estrogen agent fulvestrant. The patient demonstrated a good response, with a favorable clinical outcome as she is still in complete remission.

Conclusion
This case underscores the importance of long-term follow-up of hormone-sensitive breast cancer, including thorough clinical examinations. To the best of our knowledge, this is the first reported case of vulvar metastasis from breast cancer that was successfully treated with the combination of abemaciclib and fulvestrant, leading to a complete response. The use of CDK4/6 inhibitors for the treatment of vulvar metastases of breast origin represents a significant advance, offering a less invasive and potentially more effective alternative to current treatment protocols.