Abstract P1-15-04: Features of HER2+ metastasic patients (pts) from a prospective registry of advanced breast cancer (ABC), GEICAM/2014-03 (RegistEM)

Abstract Background: The RegistEM study is a non-interventional study that is providing prospective data from around 1900 ABC pts (females and males) diagnosed with advanced disease between 01/Jan/2016 and 31/Dec/2019, either after recurrence or at 1st diagnosis, in 38 Spanish sites representative of the national territory and whose investigators are GEICAM members. Methods: In the current analysis (cut-off date 10/May/2021, ongoing database), we describe the features of 279 pts included in the RegistEM study, with HER2+ (immunohistochemistry [IHQ] 3+, IHQ 2+ and in situ hybridization [ISH]+) tumors at any time of their ABC (5% after the 1st-line therapy). This subgroup has been evaluated because of the interest from a clinical perspective. Multivariate Cox analysis aiming to identify factors associated with overall survival (OS) were built. Results: 279 pts were identified, representing the 15% pts available in the database at the cut-off date. At first ABC diagnosis, 48% pts had recurrent BC (>12 months [mo] from initial BC diagnosis in 93%), 51% de novo metastatic BC and 1% unresectable locally advanced BC (ULABC). The median age was 59 years, 98% were white , 71% postmenopausal and only 1 male was part of this subset. Considering the BC subtype assessed in the most recent tumor lesion before the 1st-line therapy, 264 pts wereHER2 positive (67% with hormone receptor [HR]+). Family history of BC and/or ovarian cancer was reported in 31% pts, and an hereditary-risk genetic test was performed in 25% (66/267 pts). BRCA1/2 and TP53 mutations were reported in 4/20 and 4/19 pts, respectively, and p53 overexpression in 20/46 pts. Lymph nodes (56%), bone (49%), liver (34%), lung (33%), soft tissue (10%) and brain (8%) were the main metastatic sites. Additional data according to HR status and type of ABC are detailed in the table below. In HR- pts, bone metastases were less frequent and lymph nodes metastases more frequent compared to HR+ pts. Visceral disease was present in 68% pts and ≈75% had ≤3 (47% ≤2) locations involved. The most common therapies by line were: 1) 1st-line: CT + dual anti-HER2 blockade (3%), chemotherapy (CT) (almost in all pts taxane-based)+dual anti-HER2 blockade + endocrine therapy (ET) (mainly aromatase inhibitors) (35%), and ET + anti-HER2 blockade or ET + cyclin-dependent kinases 4/6 inhibitors (11%); 2) 2nd-line: anti-HER2 blockade (56%) [mostly an antibody-drug conjugate (90%)], CT + anti-HER2 blockade (18%) and ET + anti-HER2 blockade (14%); 3) 3rd-line: CT + anti-HER2 blockade (55%) and anti-HER2 blockade (22%). The median time-to-progressions to 1st-, 2nd- and 3rd-line were 14, 5, and 4 mo, respectively. A 4th-line therapy was reported in 52% of pts who received a 3rd-line. At database cut-off date, death was reported in 34% of pts. The median OS of this subset of pts was 41 mo (36-49). In a multivariate Cox regression analysis, the following variables were significantly related with worse survival (from ABC diagnosis): Brain (HR=2.62; 95% CI, 1.02-6.73) and Visceral no Brain involvement (HR=2.15; 95% CI, 1.02-4.53) compare to only soft tissue lesions; early stage at first diagnosis (HR=1.77; 95% CI, 1.15-2.73); HR- (HR=1.70; 95% CI, 1.11-2.60) and age (HR=1.04; 95% CI, 1.02-1.07). Conclusions: In this cohort of HER2+ pts with advanced disease, half of them had de novo ABC which was associated with better OS. The median PFS in 1st- and 3rd-line were slightly better in HR+ pts, and in 2nd-line was similar between HR+ and HR- cohorts. HR+181 (67%)HR- 91 (33%)Recurrent EBC134 (48%)ULABC or de novo M1 145 (52%)Time to recurrence >12 mo in EBC pts., n8435125NALocation of metastaticsites, nBoneBrainLiverLungLymph nodesSoft tissue104 10 62 57 90 1829 9 3232 64 1059 15 36 47 51 2278 6 59 46 1056Líne123123123123n180935690492613385521446333Deaths, n211112111161715141584Therapies by line, nET/BT261922101910212100ET12441011022323CT/BT/ET935031038305830CT/BT4017307581552182366924CT3572353711211BT6431373651145143385The most frequent therapies, nCT + dual anti-HER2 blockade + ET8623331551CT + single-agent HER2 blockade + ET522CT + dual anti-HER2 blockade3493644391016252CT + single-agent HER2 blockade4825641588211521CT5573354711411ET*22105212162644ET + HER2 blockade1213411662782Anti-HER2 blockade6431073651145143382Median duration of treatment, mo125585310441064TTP (mo), median (range)15(1-47)5(1-32)5(0-18)11(2-38)5(1-27)4(2-12)12 (1-47)5(1-26)4(0-17)17(2-45)7(1-32)4(1-18)Median PFS, mo14561154------HR: hormone receptor; EBC: early breast cancer; ULABC: unresectable locally advanced breast cancer; M1: metastatic; mo: month; ET: endrocrine therapy; BT: biological therapy; CT: chemotherapy; TTP: time-to-progression; PFS: progression-free survival. *ET includes aromatase inhibitors or selective estrogen receptor degraders, as single-agents or combined with cyclin-dependent kinases 4/6 inhibitors. Citation Format: Isabel Álvarez, Ángel Guerrero-Zotano, Josefina Cruz, Purificación Martínez, María Hernández, César A Rodríguez, Álvaro Rodríguez-Lescure, Silvia Antolín, Encarna Adrover, Raquel Andrés, Catalina Falo, Jose Ignacio Chacón, Ana Miguel, Sonia Servitja, Maria Galán Gramaje, Mireia Margelí Vila, César Gómez Raposo, María Jose Echarri, Rafael Villanueva, Ariadna TIbau Martorell, Silvia Varela Ferreiro, Ruth Campo, Juan Jose Miralles, Susana Bezares, Federico Rojo, Sara López-Tarruella. Features of HER2+ metastasic patients (pts) from a prospective registry of advanced breast cancer (ABC), GEICAM/2014-03 (RegistEM) [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 P1-15-04.