Recent Trends in Chemotherapy Use and Oncologists' Treatment Recommendations for Early-Stage Breast Cancer

Abstract

Background: There is growing concern about overtreatment of breast cancer as outcomes have improved over time. However, little is known about how chemotherapy use and oncologists' recommendations have changed in recent years.

Methods: We surveyed 5080 women (70% response rate) diagnosed with breast cancer between 2013 and 2015 and accrued through two Surveillance, Epidemiology, and End Results registries (Georgia and Los Angeles) about chemotherapy receipt and their oncologists' chemotherapy recommendations. We surveyed 504 attending oncologists (60.3% response rate ) about chemotherapy recommendations in node-negative and node-positive case scenarios. We conducted descriptive statistics of chemotherapy use and patients' report of oncologists' recommendations and used a generalized linear mixed model of chemotherapy use according to time and clinical factors. All statistical tests were two-sided.

Results: The analytic sample was 2926 patients with stage I-II, estrogen receptor-positive, human epidermal growth factor receptor 2-negative breast cancer. From 2013 to 2015, keeping other factors constant, chemotherapy use was estimated to decline from 34.5% (95% confidence interval [CI] = 30.8% to 38.3%) to 21.3% (95% CI = 19.0% to 23.7%, P < .001). Estimated decline in chemotherapy use was from 26.6% (95% CI = 23.0% to 30.7%) to 14.1% (95% CI = 12.0% to 16.3%) for node-negative/micrometastasis patients and from 81.1% (95% CI = 76.6% to 85.0%) to 64.2% (95% CI = 58.6% to 69.6%) for node-positive patients. Use of the 21-gene recurrence score (RS) did not change among node-negative/micrometastasis patients, and increasing RS use in node-positive patients accounted for one-third of the chemotherapy decline. Patients' report of oncologists' recommendations for chemotherapy declined from 44.9% (95% CI = 40.2% to 49.7%) to 31.6% (95% CI = 25.9% to 37.9%), controlling for other factors. Oncologists were much more likely to order RS if patient preferences were discordant with their recommendations (67.4%, 95% CI = 61.7% to 73.0%, vs 17.5%, 95% CI = 13.1% to 22.0%, concordant), and they adjusted recommendations based on patient preferences and RS results.

Conclusions: For both node-negative/micrometastasis and node-positive patients, chemotherapy receipt and oncologists' recommendations for chemotherapy declined markedly over time, without substantial change in practice guidelines. Results of ongoing trials will be essential to confirm the quality of this approach to breast cancer care.

Figure 1.

Trends in the marginal probability of a patient reporting chemotherapy receipt over time (by calendar year and quarter) by axillary lymph node involvement (node-positive, American Joint Committee on Cancer [AJCC] stage N1; node-negative/micrometastasis, AJCC stages N0 and N1mi), averaging over the demographic and clinical characteristics included in the model, as specified in the “Methods,” including the receipt of the 21-gene recurrence score and its interaction with lymph node status, in a sample of 2926 patients with estrogen receptor–positive, HER2-negative stage I–II breast cancer. The dotted lines represent the trends concurrent with the observed rate of testing, and the shaded areas represent the 95% confidence intervals. CI = confidence interval.

Figure 2.

Comparison of the effect of standardized vs changing rates of use of the 21-gene recurrence score (RS) on receipt of chemotherapy over time, stratified by axillary lymph node status (node-positive, American Joint Committee on Cancer [AJCC] stage N1; node-negative/micrometastasis, AJCC stages N0 and N1mi), in a sample of 2926 patients with estrogen receptor–positive, HER2-negative stage I–II breast cancer. Solid lines show estimated trends in chemotherapy use had there been no change in rates of RS use over time; dashed lines show the observed trends in chemotherapy use. RS = recurrence score.

Figure 3.

Trends in patients’ reports of medical oncologists’ recommendations about chemotherapy over time (by calendar year and quarter).

Figure 4.

Medical oncologists’ perspectives on recommending chemotherapy and ordering genomic testing in response to patient preference and genomic results for (A) node-negative and (B) node-positive disease.