Changing paradigms in breast cancer management: introducing molecular genetics into the treatment algorithm.

Advances in molecular genetics aimed at individualizing breast cancer treatment have been validated. We examined the use of gene assays predictive of distant recurrence in breast cancer and their impact on adjuvant treatment. A retrospective chart review of 58 T1/T2, node-negative, estrogen-receptor positive breast cancer patients that underwent Oncotype DX gene assay testing between January and December 2006 was performed. We compared treatment received after gene assay evaluation to treatment based on National Comprehensive Cancer Network guidelines. Patients were grouped using these recommendations: Low-risk group (T1a/T1b), no chemotherapy; High-risk group (T1c/T2), chemotherapy. Oncotype DX recommendations are as follows: Low recurrence risk, no chemotherapy; high recurrence risk, chemotherapy. A change in management was defined as chemotherapy for T1a/T1b disease and no chemotherapy for T1c/T2 disease. Two T1a/T1b patients had high risk of recurrence per gene assay scores and were treated with chemotherapy (P < 0.05). Eighteen T1c/T2 patients had low recurrence risk scores; 13 (72%) were spared chemotherapy. The recurrence score increased the number of patients classified as low risk of recurrence by 12 per cent and downstaged 63 per cent of high-risk patients (P < 0.003). Gene assay results changed management in 15 of 58 (26%) patients (P < 0.05). The use of gene assays allowed us to better tailor treatment in a significant number of our patients.