Published in:
01-02-2017 | Epidemiology
The influence of 21-gene recurrence score assay on chemotherapy use in a population-based sample of breast cancer patients
Published in: Breast Cancer Research and Treatment | Issue 3/2017
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Purpose
To quantify the influence of RS assay on changing chemotherapy plans in a general practice setting using causal inference methods.
Methods
We surveyed 3880 newly diagnosed breast cancer patients in Los Angeles and Georgia in 2013–14. We used inverse propensity weighting and multiple imputations to derive complete information for each patient about treatment status with and without testing.
Results
A half of the 1545 women eligible for testing (ER+ or PR+, HER2−, and stage I–II) received RS. We estimate that 30% (95% confidence interval (CI) 10–49%) of patients would have changed their treatment selections after RS assay, with 10% (CI 0–20%) being encouraged to undergo chemotherapy and 20% (CI 10–30%) being discouraged from chemotherapy. The subgroups whose treatment selections would be changed the most by RS were patients with positive nodes (44%; CI 24–64%), larger tumor (43% for tumor size >2 cm; CI 23–62%), or younger age (41% for <50 years, CI 23–58%). The assay was associated with a net reduction in chemotherapy use by 10% (CI 4–16%). The reduction was much greater for women with positive nodes (31%; CI 21–41%), larger tumor (30% for tumor size >2 cm; CI 22–38%), or younger age (22% for <50 years; CI 9–35%).
Conclusion
RS substantially changed chemotherapy treatment selections with the largest influence among patients with less favorable pre-test prognosis. Whether this is optimal awaits the results of clinical trials addressing the utility of RS testing in selected subgroups.