Oncologists' influence on receipt of adjuvant chemotherapy: does it matter whom you see for treatment of curable breast cancer?

Abstract

Purpose: We know little about whether it matters which oncologist a breast cancer patient sees with regard to receipt of chemotherapy. We examined oncologists' influence on use of recurrence score (RS) testing and chemotherapy in the community.

Methods: We identified 7810 women with stages 0-II breast cancer treated in 2013-15 through the SEER registries of Georgia and Los Angeles County. Surveys were sent 2 months post-surgery, (70% response rate, n = 5080). Patients identified their oncologists (n = 504) of whom 304 responded to surveys (60%). We conducted multi-level analyses on patients with ER-positive HER2-negative invasive disease (N = 2973) to examine oncologists' influence on variation in RS testing and chemotherapy receipt, using patient and oncologist survey responses merged to SEER data.

Results: Half of patients (52.8%) received RS testing and 27.7% chemotherapy. One-third (35.9%) of oncologists treated >50 new breast cancer patients annually; mean years in practice was 15.8. Oncologists explained 17% of the variation in RS testing but little of the variation in chemotherapy receipt (3%) controlling for clinical factors. Patients seeing an oncologist who was one standard deviation above the mean use of RS testing had over two-times higher odds of receiving RS (2.47, 95% CI 1.47-4.15), but a parallel estimate of the association of oncologist with the odds of receiving chemotherapy was much smaller (1.39, CI 1.03-1.88).

Conclusions: Clinical algorithms have markedly reduced variation in chemotherapy use across oncologists. Oncologists' large influence on variation in RS use suggests that they variably seek tumor profiling to inform treatment decisions.

Keywords: Breast cancer; Chemotherapy; Oncologist; Recurrence score assay.

Figure 1

Odds ratios (95% CI) for receipt of RS testing. This figure shows the estimated adjusted odds ratios for clinically pertinent patient factors and an attending oncologist identifier. The odds ratio listed for the oncologist effect represents the amount by which a patient’s odds of receiving RS testing are multiplied if she sees an oncologist with a propensity to use RS testing that is one standard deviation above the average oncologist’s (or in other words, an oncologist in the 84th percentile as opposed the 50th percentile for propensity to use RS).

Figure 2

Odds ratios (95% CI) for receipt of chemotherapy. This figure shows the estimated adjusted odds ratios including clinically pertinent patient factors and an attending oncologist identifier. The odds ratio listed for the oncologist effect represents the amount by which a patient’s odds of chemotherapy are multiplied if she sees an oncologist with a propensity to use chemotherapy that is one standard deviation above the average oncologist’s (or in other words, an oncologist in the 84th percentile as opposed the 50th percentile for propensity to use chemotherapy).