Impact of a scientific presentation on community treatment patterns for primary breast cancer

Abstract

Background: The publication of results from randomized clinical trials can have a dramatic effect on treatment patterns, but the impact of oral presentations at national scientific meetings is unknown. We investigated the temporal association between the oral presentation of the results from the Cancer and Leukemia Group B (CALGB) Study 9344 at the May 1998 meeting of the American Society of Clinical Oncology, which showed that paclitaxel improves survival of women with lymph node-positive breast cancer, and use of taxane chemotherapy for breast cancer.

Methods: We studied chemotherapy use in 3341 women identified through the Surveillance, Epidemiology, and End Results-Medicare database who were diagnosed with stage I-III breast cancer in 1994-1999 at age 65 years or older and received adjuvant chemotherapy, as identified through claims data, within 1 year of diagnosis. We assessed the temporal association between the CALBG presentation and taxane use with piecewise regression analysis. Multivariable logistic regression analysis was used to determine which patient characteristics were associated with taxane use.

Results: The use of taxanes increased substantially after the CALGB presentation, with absolute rates of taxane use of 5.2% before May 1998 and 23.6% in May 1998 and later. Initially, this increase was confined to patients with lymph node-positive disease (40% of whom were receiving taxanes by the end of 1999), but over time it extended to patients with lymph node-negative disease (15% of whom were receiving taxanes by the end of 1999). In multivariable analysis, patients who were treated in May 1998 or later were statistically significantly more likely to have received a taxane than patients treated before this date (estimated relative risk = 6.84, 95% confidence interval = 5.71 to 8.07). Younger patient age, larger number of lymph nodes involved, higher tumor grade, and larger tumor size were also independently associated with adjuvant taxane use.

Conclusions: The oral presentation of a single study at a national conference was temporally associated with an increase in the use of taxanes for primary breast cancer, even before study publication or Food and Drug Administration approval.

Figures

Fig. 1

Timeline of major events around the approval of paclitaxel for primary breast cancer. The U.S. Food and Drug Administration (FDA) approved the use of paclitaxel for metastatic breast cancer in April 1994 (A). Results from Cancer and Leukemia Group B (CALGB) Study 9344 were presented at the American Society of Clinical Oncology Annual Meeting in May 1998 (B). FDA approved paclitaxel for lymph node–positive primary breast cancer I October 1999 (C). In November 2000, a National Institutes of Health Consensus Conference stated that “Currently available data regarding the use of taxanes in the adjuvant treatment of women with node-positive breast cancer are inconclusive, ” (21) (D). The CALGB study was published in March 2003 (E). The position of the study cohort relative to these events is shown below the timeline.

Fig. 2

Percentage of patients on chemotherapy who received a taxane as a part of their regimen, by calendar month of first chemotherapy claim. The lines show the estimated slope of taxane use, with the knot point at February 1998. The date of the ASCO meeting at which CALGB 9344 results were presented is indicated.

Fig. 3

Percentage of patients on chemotherapy who received a taxane as part of their regimen by calendar quarter of first chemotherapy claim, according to axillary lymph node status.