Despite Early Breast Cancer Signs Test Predicts Who Could Avoid Chemotherapy
New data shows for the first time the predictive value of the 21-gene Recurrence Score (RS) assay in patients with node-positive breast cancer. The Breast Cancer Intergroup of North America trial conducted by the Southwest Oncology Group (SWOG 8814) originally showed that patients treated with 6 cycles of chemotherapy with cyclophosphamide, doxorubicin, and 5-fluorouracil followed by 5 years of tamoxifen (CAF-T) had superior disease-free survival (DFS) and overall survival (OS) compared with patients treated with tamoxifen alone. This RS assay was performed on the breast cancer tumor specimens collected on this trial, and measured the same groups of genes already in use to predict outcomes and chemotherapy benefit in lymph node-negative disease. Up until this study, standard practice was to give chemotherapy to women with positive nodes. This study sought to determine if the RS assay would be useful to predict who might avoid chemotherapy.
Dr Albain's group first showed that the RS is prognostic for 10-year DFS and OS in patients treated with tamoxifen alone. They then compared DFS in patients treated with tamoxifen versus patients treated with CAF-T across RSs. They found that there was a large and significant benefit in DFS over 10 years from adding CAF in patients with a high RS. In contrast, there was no benefit in patients with a low RS. Interaction between CAF benefit and the linear RS was significant overall and in the first 5 years. There was a strong carryover benefit of CAF in high RSs out to 10 years, but no effect whatsoever in low RSs long term. This interaction of RS with treatment effect was true in greater than or equal to 4 positive nodes and 1 to 3 positive nodes.
In summary, this work demonstrates that: (1) a very strong benefit from chemotherapy with CAF is predicted when the RS is high, and that (2) a low RS may define a group of women with positive nodes who do not appear to benefit from anthracycline-based chemotherapy.
Dr Albain concluded, "These data collectively challenge chemotherapy mandates for patients with node-positive, ER-positive disease: not all benefit from chemotherapy, whereas others derive greater benefit than previously predicted. SWOG 8814 joins a suite of studies that provide a consistent message regarding the value of the RS for individualized adjuvant therapy, and for the first time shows its value in a population of women with node-positive breast cancer who were treated with a tamoxifen-alone control. These findings should be discussed with women diagnosed with early breast cancer who fit the criteria for this study."