Abstract P1-08-14: Differences in Recurrence Score (RS) results between primary and second primary breast cancer (BC): Exploratory analysis of the Clalit Health Services (CHS) registry

Abstract Background: The first invasive disease-free survival event in patients (pts) with estrogen receptor (ER)+ early-stage breast cancer (BC) is often contralateral BC, as reflected in the TAILORx data. We analyzed the CHS registry to study differences in RS results and clinicopathological characteristics between the primary and second primary BC. Methods: This exploratory analysis included all ER+ HER2-negative BC pts who underwent RS testing through CHS between 1/2006 and 12/2020 and for whom ≥2 RS results were identified which were >1 year apart. Results: In this timeframe, 11,040 RS assays were ordered through CHS for 10,659 unique patients. The current analysis included 62 pts for whom multiple RS assays were performed >1 year apart. All 62 pts were females; their median (interquartile [IQR]) age at diagnosis was 56 (44-63) yrs, and 77% were initially diagnosed with node-negative disease. The median (IQR) time between the first and the latest RS assay was 5.3 (3.1-7.6) yrs. Tumor characteristics for the first and subsequent (second/third) primary BC tumors are presented (Table). Clinicopathologic characteristics were overall similar between the first and second/third primary BC tumors. The RS results, however, were statistically significantly higher in the second/third primary BC (P=0.0002), and the RS distribution was also significantly different with more tumors in the RS 26-100 category in the second/third primary BC (P=0.0036) (Table). The median (IQR) difference in the RS results between the first and latest RS assay for all 62 pts was 6 (-0.25-11.25). In 46 pts, (74%), the latest BC tumor had higher RS (a median [IQR] difference of 9 [5-13]) compared to the first BC tumor, and in 15 pts (24%) it had lower RS (a median [IQR] difference of -6 [-10 to -3]). One pt (2%) had the same RS result in both tumors. In 42 pts (68%), the latest primary BC was ipsilateral and in 20 pts (32%), it was contralateral. A higher RS result was observed in 33/42 (79%) of pts with ipsilateral second primary BC, and in 13/20 (65%) of pts with contralateral second primary BC (P=NS, Chi-square test). Conclusions: In ER+ HER2-negative BC pts, the characteristics of the first and second/third primary BC tumors were overall similar except for the RS result which was generally higher in the second/third primary BC. First BC; 62 tumorsSecond/third BC; 65 tumorsMedian (IQR) tumor size in the greatest dimension, cm1.55 (1.0-2.2)1.5 (1.0-1.95)Tumor size category, n (%)≤1 cm16 (25.8%)18 (27.7%)>1 - 2 cm28 (45.2%)33 (50.8%)>218 (29.0%)10 (15.4%)Unknown0 (0%)4 (6.2%)Tumor grade category, n (%)Grade 19 (14.5%)6 (9.2%)Grade 232 (51.6%)39 (60.0%)Grade 311 (17.7%)10 (15.4%)Not applicable/Unknown10 (16.1%)10 (15.4%)Histology, n (%)Invasive ductal carcinoma49 (79.0%)51 (78.5%)Invasive lobular carcinoma8 (12.9%)11 (16.9%)Mucinous/colloid/papillary2 (3.2%)2 (3.1%)Other/unknown3 (4.8%)1 (1.5%)Recurrence Score Mean (SD)a 18 (10)24 (12)Median (IQR)17 (13-22)23 (17-30)RS categoryb, n (%)0-1525 (40.3%)13 (20.0%)16-2528 (45.2%)27 (41.5%)26-1009 (14.5%)25 (38.5%)aP = 0.0002 (Mann–Whitney test); bP = 0.0036 (Chi-square test) Citation Format: Shlomit Strulov Shachar, Michelle Leviov, Rinat Yerushalmi, Karen Drumea, Margarita Tokar, Lior Soussan-Gutman, Avital Bareket-Samish, Amir Sonnenblick, Noa Efrat Ben-Baruch, Shani Paluch-Shimon, Gil Bar Sela, Salomon M Stemmer. Differences in Recurrence Score (RS) results between primary and second primary breast cancer (BC): Exploratory analysis of the Clalit Health Services (CHS) registry [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P1-08-14.