Valganciclovir

This is a phase II trial with an initial safety lead-in evaluating the efficacy, safety, neurocognitive, and quality-of-life outcomes of anti-cytomegalovirus (CMV) therapy and standard-of-care (SOC) in patients with anti-human cytomegalovirus (HCMV)-reactivated brain metastases. Male and female patients, aged ≥18 years, who have metastatic breast cancer with progressive brain metastases and CMV viremia (\> 250 copies/ml) or positive CMV IgG or IgM will be eligible to participate in the trial. Patients can proceed with SRS as long as at least 1 lesion which is 2 cm or less in a noncritical area in the brain is spared as per the discretion of treating neurosurgeon/radiation oncologist. At least 10 patients will be enrolled in the initial safety lead-in followed by the Phase II trial which will include 18 patients. Anti-HCMV therapy, oral Valganciclovir will be given to patients at 900 mg twice a day for 2 weeks. After the induction period, the maintenance will be continued with valganciclovir at 450 mg twice daily for 4 weeks (28 days).