There is a growing body of evidence supporting the omission of adjuvant chemotherapy in a subset of estrogen receptor (ER) positive (+) / Her2 receptor negative (-) breast cancer patients. We assessed recent trends in the administration of adjuvant chemotherapy thereby evaluating the role of the 70-gene signature (70-GS) testing in decision-making in the systemic treatment of lymph node negative (N0) and lymph node positive (N+) breast cancer patients.
Patients with a national guideline directed indication for 70-GS use treated between 2013-2016 were selected from the Netherlands Cancer Registry (NCR). Time trends in the administration of adjuvant chemotherapy were evaluated within guideline- and age delineated subgroups. The influence of the 70-GS on chemotherapy use was assessed with logistic regression.
During the study period, the overall administration of adjuvant chemotherapy decreased from 49% to 23%. For N0 patients, the decline in chemotherapy was independent of 70-GS use, whereas in N1a disease, the 70-GS was associated with a consistent lower proportion of patients receiving chemotherapy throughout the study period (OR 0.21 95% CI: 0.15-0.29). In patients <50 years and 50-59 years of age, the 70-GS use was associated with less chemotherapy administration and remained independently associated with less chemotherapy use after adjustment by multivariable logistic regression (OR 0.17, 95% CI: 0.13-0.23 and OR 0.53 95% CI: 0.43-0.65).
During a period that chemotherapy administration declined in ER+ breast cancer, the 70-GS contributed to the observed decrease in node positive disease and in younger patients. In N0 patients, the decline in chemotherapy use was independent of the 70-GS. A more selective use of gene-expression analyses is propagated.
Netherlands Comprehensive Cancer Organisation.
Has not received any funding.
All authors have declared no conflicts of interest.