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.