The investigators hypothesize that Guaraná, a native plant from the Amazon, might improve chemotherapy-induced fatigue in breast cancer patients undergoing treatment. In order to assess this, the investigators randomized patients to either guaraná extract or to placebo, switching the assigned treatment mid-term through the cycles of Chemotherapy.

The aim of this study is evaluate the favourable effects of Guaraná in quality of life and Fatigue in patients undergoing Chemotherapy treatment for Breast Cancer. After approval by our Institutional Review Board, we included consenting patients with a histological diagnosis of Breast Cancer for whom Chemotherapy was indicated.

Patients who agreed to participate in the study were submitted initially to a screening interview with the Brief Fatigue Inventory questionnaire from MD Anderson. If the patient presented with a severe fatigue, anemia (HB<11.0), hypothyroidism or psychiatric disorders she was excluded. If she presented with a mild or moderate fatigue the follow up continued and the patient was assessed 21 days later after her first cycle of chemotherapy with the same questionnaire. If an increase in fatigue levels occurred from mild to moderate, mild to severe or moderate to severe the patient was randomly assigned to receive either Guaraná 50mg or a placebo p.o. q12 for 21 days. At this moment the patient answered a General questionnaire, FACIT-F, FACIT-ES, HADS, Pittsburgh Sleep Quality Index and Chalder Fatigue Questionnaire (Day 1).

After the second cycle of chemotherapy the patient underwent a "wash out" period of 7 days without any intervention, and after that period she received placebo or Guaraná according to the cross over design after answering for the second time the questionnaires above (Day 29) and also the Common Terminology Criteria for Adverse Events v3.0 (CTCAE). After 21 days (Day 42) she was assessed again with the same questionnaires used in the second interview.

The patient's cancer diagnosis, treatment history, concurrent medication was recorded during the pretreatment and The Brief Fatigue Inventory was answered before each assessment.

Inclusion Criteria:

• Histological diagnosis of Breast Cancer
• Patients undergoing Chemotherapy (First Cycle)
• 18 years old or older

Exclusion Criteria:

• Hypothyroidism
• Clinical Depression
• Prior Chemotherapy
• Anemia
• Unable to sign informed consent
• Severe Fatigue