BACKGROUND Breast cancer-related lymphedema is a severe and life-long side-effect to breast cancer treatment. The condition increases the risk of infections and decreases health-related quality of life (HR-QOL) in patients. No prophylactic or curative treatment is currently available for this condition.

CD4+-cells plays a critical role in the development of lymphedema. The cells facilitate inflammation and fibrosis formation in the subcutaneous tissue which inhibits lymphatic regeneration. Tacrolimus is an immunosuppressive and anti-inflammatory macrolide that targets the CD4+-cells. Tacrolimus as treatment of lymphedema has already shown promising results in animal studies. Tacrolimus has the potential to cure an otherwise uncurable and life-long side-effect of BC and will therefore benefit a large number of patients who suffers from BCRL.

AIM To assess the effect of Tacrolimus treatment on breast cancer-related lymphedema METHOD Study design A pilot study with a planned inclusion of 20 patients with a 12 month follow-up period. The purpose of this study is to assess the effect of tacrolimus treatment on lymphedema and HR-QOL. Results are attained from objective measures and questionnaires.

The patients will be seen at a consultation prior to the treatment start and then 3 times hereafter (at 3, 6 and 12 months) as follow up consultations where effect of treatment is evaluated.

Primary endpoint:

- Arm volume measured with water displacement test.

Secondary endpoints:

• Arm volume measured with measuring tape and calculated with volume of a cone formula
• Patient-reported outcome measured through the Danish versions of , LYMPH-ICF, DASH and SF-36 questionnaires
• Bioimpedance
• Lymphangiography Primary- and secondary endpoint data will be collected at each of the 3 consultations (prior to treatment and 3 and 6 months after the treatment start).

CLINICAL IMPACT This will be the first clinical pharmacological study on regarding treatment of lymphedema with Tacrolimus. This study will test the feasibility and efficacy of Tacrolimus ointment in a population of breast cancer patients who have developed lymphedema. The study may lead to a routine clinical implementation of tacrolimus ointment to patients diagnosed with Lymphedema. Regardless of the outcome, the study will benefit the patients and future research in the field of lymphedema.

Inclusion Criteria:

• Age between 30-65 years
• Female
• Lymphedema diagnosis as a result of breast cancer treatment
• Active Lymphedema (excessive fluid)
• Significant lymphedema
• Grade I-II lymphedema
• Postmenopausal (Absence/lack of menstruation in at least 12 consecutive months) or continuously usage of contraceptive drugs (Spiral, birth-control pills, implant, transdermal patches, vaginal ring or depot injection). Contraceptive drugs must be used throughout the project and at least three weeks subsequent to the ending of the project (last application of the ointment).
• Clinically good general condition No lymphedema in the opposite arm (normal arm)
• Understands the purpose og the study and gives written consent to participate
• Can read and understand the danish language

Exclusion Criteria:

• Pregnant, breast-feeding or with wish of pregnancy within the next year
• Bilateral breast cancer
• Grade 0, III or IV lymphedema
• Known allergies for Tacrolimus or and other macrolide
• Removal of lymph nodes in the opposite armpit
• Suffers from psychiatric disorders that may affect the participation in the project
• Reduced kidney or liver function
• Defect skin-barrier
• Diagnosed immunodeficiency