[53] Risk of distant recurrence using oncotype DX in postmenopausal primary breast cancer patients treated with anastrozole or tamoxifen: a TransATAC study.

Dowsett M, Cuzick J, Wales C, Forbes J, Mallon L, Salter J, Quinn E, Bugarini R, Baehner FL, Shak S, on Behalf of the ATAC Trialists' Group Royal Marsden Hospital, London, United Kingdom; Wolfson Institute for Preventive Medicine, London, United Kingdom; Newcastle Mater Hospital, Newcastle, Australia; Royal Infirmary, Glasgow, United Kingdom; Genomic Health Institute, Redwood, CA

Background: The Recurrence Score (RS) has been validated for estimating residual risk of distant recurrence (DR) in ER+ node negative (N-) primary breast cancer patients receiving adjuvant tamoxifen. Aromatase inhibitors (AIs) are widely used for adjuvant treatment of ER+ disease in postmenopausal women. The RS has not been evaluated in patients treated with an AI.
Method: Tumour blocks were collected retrospectively from patients in the monotherapy arms of the ATAC trial under the TransATAC protocol yielding 1308 hormone receptor positive (HR+) blocks in UK patients for analysis (1). Cox proportional hazards model was used to test the significance of adding RS to a clinical model (age, tumour size, grade, treatment) and to Adjuvant! Online.
Results: 65 patients received chemotherapy, 4 were centrally HR negative and 8 did not start adjuvant therapy leaving 1231 evaluable patients of which 872, 306 and 53 were N-, N+ and N unknown in whom there were 72, 74 and 6 DRs, respectively. In the prospectively-defined primary multivariate analysis tumour size, grade and RS were each separately statistically significant in predicting time to DR in N- patients (p<0.001, 0.003 and <0.001, respectively). Similar results were seen in N+ patients. The 9-year rates of DR by nodal status for the pre-specified RS groups are shown in the table. RS showed statistically significant prognostic value beyond that provided by Adjuvant! Online in both N- (p<0.001) and N+ patients (p=0.003).

Nodal status	RS <18		RS 18-30		RS >/=31		Log-rank p-value for DR
	% of pts	9-yr DR rate	% of pts	9-yr DR rate	% of pts	9-yr DR rate
Node negative	59%	4%	26%	12%	15%	25%	<0.001
Node positive	52%	17%	31%	28%	17%	49%	<0.001

Conclusions: Oncotype DX RS is an independent predictor of the risk of distant recurrence in N- and N+ HR+ patients treated with anastrozole or tamoxifen. The data are not predictive of a differential benefit between anastrozole and tamoxifen.
(1) Dowsett et al JCO 2008, 26, 1059.

Saturday, December 13, 2008 10:00 AM

General Session 5 (9:30 AM-11:30 AM)