Stanford, CA—With growing concern about overtreatment of breast cancer as outcomes have improved over time, not much research has been performed on how chemotherapy use, and oncologists’ recommendations, have changed in recent years.

A new study published online by the Journal of the National Cancer Institute sought to fill that gap.

A study team led by Stanford University researchers surveyed 5,080 women identified through two surveillance, epidemiology, and end results registries from the state of Georgia and the city of Los Angeles. Participants, who responded at a 70% rate, had all been diagnosed with breast cancer between 2013 and 2015.

The patients were asked about the chemotherapy they received, as well as their oncologist’s recommendations. At the same time, researchers surveyed 504 attending oncologists (60.3% response rate) about chemotherapy recommendations in node-negative and node-positive case scenarios. The analytic sample was 2,926 patients with stage I-II, estrogen receptor-positive, human epidermal growth factor receptor 2–negative breast cancer. 

Results indicated that, from 2013 to 2015, other factors kept constant, chemotherapy use was estimated to decline from 34.5% to 23.7%. Estimated decline in chemotherapy use was from 26.6% to 14.1% for node-negative/micrometastasis patients, and from 81.1% to 64.2% for node-positive patients. 

In trying to determine why that might have occurred, study authors report that use of the 21-gene recurrence score (RS) did not change among node-negative/micrometastasis patients, although increasing RS use in node-positive patients accounted for one-third of the chemotherapy decline. The RS assay is used to predict disease recurrence and the benefit of chemotherapy in estrogen receptor–positive, lymph node–negative early-stage breast cancer (EBC). Oncologists were much more likely to order it if patient preferences were at odds with their recommendations —67.4% versus 17.5%—but they also adjusted recommendations based on patient preferences and RS results.

Part of the issue appeared to be that oncologists didn’t recommend chemotherapy as often. Based on patient reports, researchers determined that oncologists’ recommendations for chemotherapy declined from 44.9% to 31.6% controlling for other factors. 

“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,” study authors concluded. “Results of ongoing trials will be essential to confirm the quality of this approach to breast cancer care.”
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