The use of genomic assays reduces rates of chemotherapy: a single-institution experience.

Introduction: The National Institute for Clinical Excellence recommends the use of tumour profiling tests to guide adjuvant chemotherapy in breast cancer. The Oncotype DX™ score (Genomic Health) has superseded more traditional tools such as PREDICT in appropriate patients (ER + ve, HER2-ve, lymph node negative and with a Nottingham Prognostic Index [NPI] ≥ 3.4). The aim of this study was to see whether the introduction of Oncotype DX within our institution resulted in an overall reduction in rates of chemotherapy.

Method: Data was collected retrospectively using the Somerset Cancer Register, Pathology department databases and the institution's own online medical records system. Two groups were compared: (1) pre-oncotype (Jan 2012-Dec 2014) and (2) post-oncotype (Jan 2016-July 2018).

Results: During the pre-oncotype period, 28/82 (34%) patients who would have been eligible for testing (patients who were ER + ve, HER2-ve, and a NPI ≥ 3.4) received chemotherapy compared to 34/135 (25%) who were sent for oncotype during the second study period (p = 0.157). For grade 3 cancers, and those aged under 50, the results were more marked: grade 3 pre-oncotype 23/43 (53%), post-oncotype 29/76 (38%) (p = 0.101), aged under 50 pre-oncotype 8/15 (53%), post-oncotype 10/31 (32%) (p = 0.197).

Conclusion: Within our institution, overall rates of chemotherapy have reduced since the introduction of Oncotype DX with the results more marked in subgroups of traditional indicators of tumour aggression. As genomic assays provide a more accurate prediction of the benefit of chemotherapy, its overall reduction has potential cost saving implications as well as reducing risk in patients who will derive little benefit.