Abstract P5-07-03: Prosigna® results impact on adjuvant decision making in early breast cancer (EBC): Final analysis of the prospective WSG study

Background: Prosigna is a standardized test measuring expression levels of 50 classifier genes (PAM50) in breast tumor tissue using nCounter ® Technology (Nanostring Technologies, Inc.). It provides intrinsic subtype and risk of recurrence (ROR) score predicting 10-year recurrence probability. WSG prospectively evaluated Prosigna9s impact on therapy decisions in EBC and the quality assurance at its implementation in clinical routine. Methods: The study recruited 201 consecutive postmenopausal patients in 11 centers with ER+ HER- N0 EBC (10/2013 to 10/2014). Its primary objective was to assess the extent to which the Prosigna (Breast Cancer Intrinsic Subtype Test (BCIST)) affects the oncologists9 treatment recommendations regarding adjuvant chemotherapy (CT) and actual treatments received for EBC patients. Changes in treatment recommendations include (1) endocrine therapy alone, (2) endocrine therapy plus CT, and (3) changes in types of CT before/after the test and confidence in this treatment decision from physician and patient at a 6-month follow up. Secondary objectives included information on (1) physicians9 confidence in the recommendations before/after the test, and by cancer recurrence risk groups, (2) rate of CT related adverse events stratified by administration of CT, and (3) patients9 decisional conflict status, anxiety levels, and functional status before/after Prosigna9s results. As a secondary endpoint for quality assurance, we repeated Prosigna in a second decentralized pathology laboratory in Germany for inter-observation control. Results: In the total evaluable cohort (n=198), 114 (57.6%) of tumors were classified by Prosigna as Luminal A, 79 (39.9%) Luminal B, 3 (1.5%) Basal-like and 2 (1%) HER2-E. Median Prosigna ROR score was 45 (0-94). There was a 29.3% discordance in intrinsic subtyping between Prosigna and IHC. Concordance between central pathology and the second lab regarding molecular subtype was 95.5% with only 9 discordant samples, all within the luminal group. Concordance regarding ROR risk group classification was 92.9%; no clinically relevant differences (low-high or vice versa) were seen. Overall, there was a change of treatment choice (change in CT indication and change in regimens) in 18.2% compared to the pre-Prosigna decision. Post-Prosigna, 87.8% of physicians felt more confident with their prognostic assessment and 89.4% with their intended treatment. 94.8% of the patients expected to stick to their decision after discussing the Prosigna results. Six-month follow up (actual CT administered, its morbidity, perceptions by physicians and patients) will be presented at SABC. Conclusion: Overall, there was a change of treatment choice (change in CT indication and change in CT regimens) in 18.2% compared to the pre-Prosigna decision. Substantial discordance between Prosigna (PAM50) and local IHC underlines the importance of molecular subtyping prior adjuvant treatment decisions. High concordance of Prosigna results between central and decentralized lab testing were found. Results of WSG study can be pooled with two similar European studies and may thus help to improve our understanding of treatment decision making and adherence in EBC. Citation Format: Wuerstlein R, Sotlar K, Gluz O, Hofmann D, Otremba B, Von Schumann R, Witzel I, Schindlbeck C, Janni W, Schem C, Bauerfeind I, Hasmueller S, Tesch H, Paulenz A, Morel P, Cowens W, Hornberger J, Kates RE, Pelz E, Harbeck N. Prosigna® results impact on adjuvant decision making in early breast cancer (EBC): Final analysis of the prospective WSG study. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P5-07-03.