Factors influencing Oncotype DX use in the management of early breast cancer: a single centre experience.

BACKGROUND

Oncotype DX recurrence score is a multi-gene assay which quantifies the risk of distant recurrence in patients with hormone receptor-positive (HR+) early breast cancer (EBC) treated with tamoxifen, and predicts the magnitude of clinical benefit of adjuvant chemotherapy. This retrospective study examined factors that were associated with use of Oncotype DX assay at a tertiary care cancer centre in Ottawa, Canada.

METHODS

One hundred consecutive patients (pts) diagnosed with HR+, HER2/neu negative EBC (stage I-II), who underwent Oncotype DX testing (Test Group) between 1st April 2010, and 30th June 2011 were included in the study. A second cohort of 100 randomly selected patients with HR+, HER2/neu negative EBC diagnosed from the same time period who did not receive Oncotype DX testing were used as the control group (Control Group). Demographic and clinicopathologic data were obtained from review of charts. Logistic regression was performed to identify variables associated with Oncotype DX usage.

FINDINGS

Median age was 58 years (r: 26-77) in Test Group and 63 years (r: 30-81) in Control Group. Sixty-two patients in the Test Group had T1 tumours, compared with 71 in the Control Group. The median 10-year recurrence risks from Adjuvant! Online were 19% and 12% in the Test Group and Control Group, respectively. Factors significantly associated with the utilisation of Oncotype DX assay on multivariate analysis include age 50-64 (p=0.049), tumour size 10.1-20mm (p=0.008) and grade 2 histological grade (p=0.004).

INTERPRETATION

Usage of Oncotype DX assay is associated with several clinicopathological factors. These factors reflect the clinical uncertainty of benefit from chemotherapy in these subpopulations of patients and suggest how Oncotype DX assay could complement clinicopathological factors in helping clinicians on treatment selection.