Prognostic and predictive value of the 21-gene recurrence score assay in postmenopausal, node-positive, ER-positive breast cancer SWOG 8814 / TBIC 0100.  (Oral Presentation 10)

This study presented at the 2007 SABCS conference had two primary aims: to determine if the Recurrence Score (RS) provides prognostic information for post-menopausal women with lymph node-positive, estrogen-receptor positive, stage II-III breast cancer treated with tamoxifen only; and to determine if the RS predicts the magnitude of chemotherapy benefit (CAF) in this group.

The study was limited to the tamoxifen and sequential chemotherapy + tamoxifen arms in patients with positive lymph nodes, and used Disease Free Survival (DFS) at ten years as an endpoint.  The sample size was 367 patients, with 148 receiving tamoxifen alone versus 219 receiving sequential CAF chemotherapy followed by tamoxifen.

The distribution of Recurrence Scores in this node-positive sample broke out as follows:

• 40% of patients in the study were low risk with an RS between 1 and 17
• 28% of patients were intermediate risk, with an RS between 18 and 30
• 32% of patients were high risk, with an RS of 31 or above

The DFS in tamoxifen-treated patients was 60% in the low risk category, compared to 49% in the intermediate range, and 43% in the high risk range.  The analysis looked at the difference in DFS between the low and high risk groups, and was statistically significant (p = 0.017) at ten years.  These results establish the performance of the Recurrence Score in assessing prognosis in post-menopausal female patients with stage II-III node-positive, ER-positive breast cancer. 

With respect to predicting the benefit from adding CAF chemotherapy to tamoxifen, patients with low Recurrence Scores showed minimal if any benefit from the chemotherapy, as there was no significant difference in DFS in the tamoxifen-only arm versus the CAF-T arm.  However, patients with high Recurrence Score results showed substantial benefit from adding CAF chemotherapy to tamoxifen.  This abstract did not report an estimate of chemotherapy benefit for node-positive women with intermediate Recurrence Scores, so the benefit of undergoing chemo for that group of patients cannot currently be ruled out.