A retrospective study of women with metastatic breast cancer shows that the biological characteristics of their primary tumors - including estrogen, progesterone, and HER2 status - often changes when cancer spreads to the liver, requiring a change in therapy in more than 12 percent of patients.

"These results indicate that tumor biology often changes between primary and metastatic lesions, and suggest that biopsies of these secondary tumors should be performed whenever feasible," said co-author Giuseppe Curigliano, M.D., Ph.D., senior deputy director in the division of medical oncology at the European Institute of Oncology in Milan, Italy. "Traditionally, we start therapy according to the biological features of the primary tumor, and these results can influence treatment choices as many as 10 years later. Retesting secondary tumors will help us ensure that patients get the most effective therapy possible, which can have a dramatic impact on their overall outcome."

The choice of therapy for women with breast cancer is based on the status of key biological markers, such as estrogen and progesterone receptors and HER2. For example, trastuzumab (Herceptin) is only effective in women whose tumors overproduce HER2, while tamoxifen or aromatase inhibitors only work in breast cancer patients with estrogen receptor-positive tumors. But doctors don't routinely biopsy metastases, relying on the results of the primary tumor biopsy to guide treatment -- sometimes for many years.

In this study, researchers examined biopsy data from primary breast tumors and liver metastases in 255 women with metastatic breast cancer to determine the status of estrogen and progesterone receptors and HER2. They found changes in estrogen receptor status in the secondary tumor in 14.5 percent of women, progesterone status in 48.6 percent and HER2 status in 13.9 percent. This led to changes in therapy in 12.1 percent of the patients.