Trends in Use of Adjuvant Multi-Agent Chemotherapy and Tamoxifen for Breast Cancer in the United States: 1975-1999

BACKGROUND: Understanding trends in the dissemination of findings from clinical research can help in estimating their population-level benefits. We evaluated trends in the use of adjuvant multi-agent chemotherapy, tamoxifen, and the combination of both treatments for early-stage breast cancer in the United States from 1975 through 1999. METHODS: Data on treatment of 217 508 patients diagnosed from 1975 through 1999 with stages I, II, and IIIA breast cancer were obtained from eight registries of the Surveillance, Epidemiology, and End Results (SEER) Program. Models of dissemination were developed from these data after adjustment based on information from a series of population-based Patterns of Care (POC) studies that randomly selected case patients from the SEER registries. The POC studies included 7116 patients diagnosed from 1987 through 1991 and in 1995 who were eliminated from the SEER data used in this analysis. RESULTS: The modeled disseminations were generally compatible with the POC-observed proportions of each treatment. The use of multi-agent chemotherapy was higher among premenopausal women, and the use of tamoxifen was higher among postmenopausal women. The use of multi-agent chemotherapy for postmenopausal women diagnosed with lymph node-positive stage II+ or stage IIIA cancer reached a peak in 1983 and then decreased through 1986, indicating its substitution with tamoxifen. After 1986, the combined use of multi-agent chemotherapy and tamoxifen increased for almost all stages and ages. After the early 1990s, tamoxifen use in postmenopausal women with stage II+ or stage III breast cancer declined. CONCLUSIONS: The observed dissemination patterns suggest that the results of clinical trials are disseminated fairly rapidly to community-based physicians and their patients.