The survival benefits of longer-term therapy using tamoxifen may take at least nine years to develop, according to a new study published in the December 1, 2005 issue of Cancer, a peer-reviewed journal of the American Cancer Society.
A long-term study evaluating two versus five-year treatment with tamoxifen in women aged 50 years or older found it took nine years to demonstrate significant survival benefits of the longer-term treatment, and that improvements in survival were observed only in postmenopausal women younger than 55 years and with estrogen receptor (ER) positive tumors. In these patients prolonging tamoxifen to five years was associated with a 44 percent reduction in the risk of death.
While tamoxifen is the generally accepted as the standard of care for breast cancer after surgery for its demonstrated improvements in survival, the duration of therapy and the length of time to find significant survival improvements remain unclear. Data consistently suggest that longer duration of treatment results in longer disease-free survival. Data conflicts, however, on whether longer treatment results in longer overall survival and whether it takes many years after treatment to see its benefits.