Temozolomide as a Prophylaxis Against Brain Recurrence in Participants With Metastatic Breast Cancer (P05225 AM2)

Inclusion Criteria:

* Diagnosis of metastatic breast cancer.
* Participants must have completed first line of metastatic chemotherapy and have achieved complete or partial response or disease stability for at least 6 months from the first confirmation of disease stabilization.
* No clinical sign of brain progression.
* At least one of the following 3 conditions: HER2 +++, Young age (\< 50 years), and/or estrogen receptor (ER)-/progesterone receptor (PgR)-
* Eastern Cooperative Oncology Group (ECOG) performance status ≤2.
* Life expectancy ≥3 months.
* Neutrophils ≥1.5 x 10\^9/L, platelets ≥100 x 10\^9/L, hemoglobin ≥9 g/dL, lymphocytes ≥1 x 10\^9/L.
* Bilirubin level either normal or \<1.5 x ULN (upper limit of normal).
* AST (aspartate aminotransferase) and ALT (alanine aminotransferase) ≤2.5 x ULN (≤5 x ULN if liver metastases are present).
* Serum creatine \<1.5 x ULN.
* Effective contraception if the risk of conception exists.

Exclusion Criteria:

* Concurrent chronic systemic immune therapy not indicated in the study protocol.
* Any investigational agent(s) within 4 weeks prior to entry.
* Participants that have completed 2nd, 3rd, or 4th line metastatic chemotherapy or participant in active chemotherapy treatment.
* Clinically relevant coronary artery disease or a history of a myocardial infarction within the last 12 months.
* Acute or sub acute intestinal occlusion or history of inflammatory bowel disease.
* Known Grade 3 or Grade 4 allergic reaction to any of the components of the treatment.
* Known drug abuse/alcohol abuse.
* Legal incapacity or limited legal capacity.
* Medical or psychological condition which in the opinion of the investigator would not permit the participant to complete the study or sign meaningful informed consent.
* Women who are pregnant or breastfeeding.
* Any concurrent malignancy other than non-melanoma skin cancer, or carcinoma in situ of the cervix (participants with a previous malignancy but without evidence of disease for ≥5 years will be allowed to enter the trial).