Results from an open-label, phase II, randomized clinical trial comparing docetaxel alone or in combination with PANVAC, a viral-vector cancer vaccine, in patients with metastatic breast cancer suggest that the vaccine may have some clinical benefit. The vaccine encodes for transgene CEA and MUC-1, as well as three costimulatory molecules. 

A total of 48 patients were randomized in the six-year study between May 2006 and February 2012. The patient and tumor characteristics were matched. Progression-free survival was 7.9 months with docetaxel and PANVAC, compared with 3.9 months for docetaxel alone. 

Patients received weekly docetaxel with or without PANVAC. The patients in the combination therapy arm received a priming dose of PANVAC three weeks before the first docetaxel dose and boosters on the first day of every docetaxel treatment. The patients in the combination arm received a median of five docetaxel cycles, and patients in the control arm received a median of three cycles. Patients in the combination group showed an increase in grade 1 and 2 edema, possibly associated with greater number of docetaxel doses, as well injection site reactions. 

According to the researchers, the results suggest that a cancer vaccine combined with standard chemotherapy agents may have some clinical benefit for patients with metastatic breast cancer. Further studies to identify a biomarker that predicts which patients are most likely to benefit from this approach are planned.