Abstract 644: Tumor circadian dysfunction is associated with improved survival in breast cancer patients on neoadjuvant chemotherapy (NAC)
Authors: Giacchetti Sylvie , Vlachou Denise , Bjarnason Georg A. , Rand David A. , Levi Francis A. 
Published: July 2021

Abstract
Introduction Previous studies highlighted the relevance of circadian rhythms for carcinogenesis and therapy in breast cancer. These rhythms are generated in each cell by a molecular clock. We have developed a machine-learning approach (TimeTeller) and constructed an algorithm to measuring circadian clock functionality from the expression levels of clock genes in a single tissue sample (Vlachou et al. Rxiv 2020).
Methods TimeTeller was used to analyse tumor molecular clock dysfunction in biopsies from 226 breast cancer patients prior to NAC. Tumour transcriptome was determined using the Affymetrix U133A (Giacchetti et al. EJC 2017). A measure Θ of the level of dysfunction of the cellular clock was computed using TimeTeller, based on the relative mRNA expressions of 16 clock genes, which displayed largest circadian expressions in healthy mouse and human tissues sampled at &gt; 6 circadian times. Thus Θ &lt; 0.1 was indicative of a functional clock in humans irrespective of sampling time. To determine the prognostic value of continuous Θ for breast cancer patients'survival at ten years, we calculated the hazard ratios (HRs) associated with overall survival (OS) and disease-free survival (DFS) of the 226 patients receiving NAC, using the Cox proportional hazards model. HR1/10 corresponded to the risk of an earlier death or relapse for a change of 0.1 in Θ.
Results: The breast cancer Θ values ranged from 0.02 to 0.29, with a median of 0.058 [IQR, 0.09]. As compared to patients whose tumor Θ was &lt; median, patients with tumor Θ&gt;median had higher survival rate (71% vs 81%, p = 0.01) and DFS rate, 65% vs 74%, p = 0.02) at 10-years. Multivariate analyses identified continuous Θ as an independent prognostic factor for both OS (HR1/10, 0.38 [0.17-0.84] (p = 0.016) and DFS (HR1/10, 0.46 [0.27-0.80] (p = 0.005), jointly with tumor size for OS (HR1/10, 1.73 [1.12-2.70], p =0.014) and HER2 for DFS (HR1/10, 0.43 [0.23-0.79], p = 0.007). The relevance of Θ was further explored in the three main breast cancer categories. In the HER2+ subset, the HR associated with Θ was 0.19 for OS (p=0.058) and 0.22 for DFS (p=0.048, single significant prognostic factor). The HR1/10 increased to 0.45 for OS and 0.57 for DFS in the HER2-/hormonal receptors + subset, and to 0.45 and 0.46 respectively for the TN group (p&gt;0.10), suggesting a lesser independent prognostic effect of Θ in these subsets. The patients who achieved pCR had a higher median Θ as compared to those who did not (p = 0.035), supporting increased chemosensitivity of those tumors with clock dysfunction to conventional NAC
Conclusion: In this population of women on NAC for primary breast cancer, tumor circadian clock dysfunction, as computed by the TimeTeller algorithm, was the strongest independent predictor of survival. Thus, conventional chemotherapy efficacy may be enhanced in tumors with deregulated metabolism and proliferation, as a result of circadian clock dysfunction.
Citation Format: Sylvie Giacchetti, Denise Vlachou, Georg A. Bjarnason, David A. Rand, Francis A. Levi. Tumor circadian dysfunction is associated with improved survival in breast cancer patients on neoadjuvant chemotherapy (NAC) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 644.