Abstract P1-09-06: Prognostic and predictive relevance of cell cycle progression (CCP) score in ductal carcinoma in situ: Results from the UK/ANZ DCIS trial

Abstract

Abstract Background: The prognostic abilities of most gene expression signatures in breast cancer are often due to detection of proliferative activity measured from expression of genes regulated as a function of cell cycle progression. Cell Cycle Progression (CCP) score is an important prognostic factor in prostate cancer, and has shown promising results for renal and lung cancer; its role in ductal carcinoma in situ (DCIS) has not been explored. We investigated the prognostic and predictive relevance of CCP Score in DCIS using material from UK/ANZ DCIS trial. Methods: Formalin-fixed paraffin embedded tissues were collected from patients enrolled in the UK/ANZ DCIS trial, a randomised 2X2 factorial design trial investigating role of tamoxifen, radiotherapy (RT) or both as adjuvant treatment in DCIS. mRNA expression of 25 S- and M-phase CCP genes was evaluated by reverse transcription followed by PCR on customized Taqman low-density arrays. CCP score is an un-weighted average of the expression values of CCP genes after normalisation with 14 housekeeping genes. CCP score was analysed as a continuous variable and also as an ordinal variable using tertile-based cut-offs. Exploratory analyses with subgroups defined by HER2 status by immunohistochemistry were performed. Results: CCP scores were evaluable in 521 (134 recurrence events) of 704 available samples (DCIS absent or insufficient RNA in 51, assay failure in 132). Increase in CCP score (median 1.15; IQR 0.71-1.74) was associated with increased risk of ipsilateral breast event (IBE) [Hazard ratio (HR) = 1.28; 95% Confidence Interval (95%CI) 1.08-1.51; p = 0.0049]. CCP score however was not an independent predictor in multivariate analyses [HR = 1.16; 95%CI 0.95-1.42; p = 0.14]. CCP scores were categorised as CCP low (<0.87), CCP intermediate (>/= 0.87 to < 1.52) and CCP high (>/= 1.52) by tertiles. The benefit of RT in reducing IBE was significant when CCP score was low [HR = 0.35; 95%CI 0.14-0.87; p = 0.024] or intermediate [HR = 0.23; 95%CI 0.09-0.59; p = 0.0023], however, those with high CCP score did not derive significant RT benefit [HR = 0.59; 95%CI 0.31-1.13; p = 0.11]. In exploratory subgroup analyses, HER2 negative DCIS with high CCP score (20.9% of all DCIS cases) did not derive RT benefit and the largest RT benefit was seen for DCIS that expressed HER2 and did not have a high CCP score (23.2% of all DCIS cases). Benefit of RT and 10-year IBE rates by CCP score (categorised) and HER2 status subgroups.SubgroupneventsHR (95%CI)p10-year IBE rates (%) - No RT10-year IBE rates (%) - RTCCP-high & HER2 neg106220.83 (0.35-1.97)0.6722.5 (14.0-35.0)20.0 (10.5-36.0)CCP-high & HER2 pos67210.43 (0.16-1.17)0.09840.6 (27.1-57.6)20.4 (8.9-42.9)CCP-non-High & HER2 neg217300.43 (0.18-0.99)0.04816.2 (10.7-24.0)8.1 (4.0-16.3)CCP- non-High & HER2 pos118330.14 (0.04-0.46)0.001239.5 (29.3-51.6)7.1 (2.3-20.4)CCP-non-High = low or intermediate CCP score Conclusions: CCP score is not independently associated with the risk of IBE but appears to be a predictor of RT benefit. Exploratory analyses suggest that combined with HER2 status, it may help in identifying a large DCIS subgroup where RT is highly indicated and another large subgroup where mastectomy may be merited. Citation Format: Thorat MA, Wagner S, Jones LJ, Levey PM, Bulka K, Hoff R, Sangale Z, Flake II DD, Bundred NJ, Fentiman IS, Forbes JF, Lanchbury JS, Cuzick J. Prognostic and predictive relevance of cell cycle progression (CCP) score in ductal carcinoma in situ: Results from the UK/ANZ DCIS trial [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P1-09-06.