[48] Relationship between quantitative ER and PgR expression and HER2 status with recurrence in the ATAC trial.

Dowsett M, Allred DC, on Behalf of the TransATAC Investigators.. Royal Marsden Hospital, London, United Kingdom; Baylor College of Medicine, Houston, TX

Purpose: To determine the relationship between quantitative estrogen receptor (ER) and progesterone receptor (PgR) expression and human epidermal growth factor receptor 2 (HER2) status with disease recurrence, in primary ER+ and/or PgR+ breast cancer patients treated with adjuvant anastrozole (A) or tamoxifen (T) in the Arimidex, Tamoxifen, Alone or in Combination (ATAC) trial (ISRCTN18233230).
Background: The ATAC trial randomized 9366 patients to 5 years treatment with A or T or the combination. Following analysis of the results of the main ATAC trial at a median follow-up of 33 months, the combination arm was discontinued since it was no more effective than T alone. After a median follow-up of 68 months, it was found that A prolonged disease-free survival significantly compared with T in ER+ and/or PgR+ patients (hazard ratio 0.83; 95% confidence intervals 0.73, 0.94; p=0.005). ER, PgR and HER2 expression have each been reported to influence responses to aromatase inhibitors and T differentially.
Materials and Methods: Retrospective consent to tumor block collection and biomarker analysis was sought from patients with ER+ and/or PgR+ tumors in the A or T arms (total number eligible: 5880). Tissue sections were cut and tissue microarrays (TMAs) were constructed. Immunohistochemical stains for ER (Novocastra 6F11 on TMAs), PgR (Novocastra 312 on sections) and HER2 (DAKO HercepTest on sections) were performed. Scoring systems were ER: H-score; PgR: percentage of positive cells; HER2: staining classification on a scale of 0 to 3+ (positive status 3+ or 2+ if confirmed by FISH). Relationships between biomarker expression and recurrence will be assessed by proportional hazards analysis.
Results: 1792 blocks (30% of total eligible) have been collected and are being tested. All blocks collected by the end of September 2006 will be analyzed. A total of >2000 blocks is anticipated at that time. Acknowledgements: We are grateful to the many investigators and pathologists who have collaborated in this work. Financial support was provided by grants from AstraZeneca and Breakthrough Breast Cancer.

Sunday, December 17, 2006 11:15 AM

General Session 7 (9:00 AM-11:30 AM)