Abstract PS7-25: Geicam/2014-03 (RegisTEM): A prospective registry of unresectable locally advanced or metastatic breast cancer: Characteristics of a subset of patients with triple negative subtype
Authors: Jara Carlos , Rodríguez César A. , Alvarez Isabel , Falo Catalina , Martínez Purificación , Andrés Raquel , Cruz Josefina , Mori Marta , Adrover Encarna , Tibau Ariadna , Antolin Silvia , Margeli Mireia , Alonso Jose L. , Pajares Bella I. , Camara M. Carmen , Miralles J. Jose , Bezares Susana , Rojo Federico , López-Tarruella Sara , Zotano Angel Guerrero- 
Published: February 2021

Background: There is limited prospective data for advanced breast cancer (ABC) patients (pts), both unresectable locally (ULABC) or metastatic (MBC) treated as per clinical practice. RegistEM study will provide epidemiological, pathological and clinical data, including treatments for different disease settings. Understanding the real distribution of BC subtypes is the primary objective. This is a non-interventional cohort study that will enroll around 1,867 pts (males or females) with ABC diagnosed from January 2016 to December 2019, either after recurrence or as first diagnosis, in 38 Spanish sites. Triple negative (TN) subtype histologically confirmed in the primary tumor (PT) and/or in a metastatic tumor lesion (M1) and recurrent disease from early stage, has been identified as an interesting group from a clinical perspective for detailed analysis. Methods: In this analysis, we describe the characteristics of 131 pts with TN subtype by local evaluation at any disease stage [in PT only (PT group), in M1 only (M1 group) and in both PT and M1 (group PT/M1)] until progressive disease (PD) at first-line and data of therapeutic options at second-line. Results: Distribution of 131 pts within the groups; PT, M1 and PT/M1, was 45.8%, 27.5% and 26.7%, respectively. To date, 32.1% pts have shown a change of subtype along their BC evolution, &gt;50% of those changes was between TN and Luminal B HER2-. Median time from early BC (EBC) diagnosis until recurrent disease in terms of MBC or ULABC was 33.4 months (mo) (PT and PT/M1-26.0 mo; M1-60.2 mo), with the majority of pts recurring &gt;12 mo (91.6%). Median age at diagnosis of ABC was 58 years (range 31-84), most pts were Caucasian (96.9%), female (99.2%) and postmenopausal (65.6%). Family history of BC and/or ovarian cancer was reported in 41.2% pts, a hereditary-risk genetic test was performed in 21.4% pts (8 pts with BRCA1/2 mutation). Lung (40.5%), lymph nodes (35.9%), bone (35.9%) and liver (20.6%) were the most frequent metastatic locations; central nervous system metastases were developed by 12.2% pts. The rate of visceral involment (60-70% pts) was similar among the 3 subgroups. The most frequent first-line therapies were chemotherapy (CT) (51.1%) and CT/biological therapy (BT) (32.8%). Most pts (68.7%) received CT in monotherapy (capecitabine 50%, taxanes 26.1%). Bevacizumab was the most frequent BT within the CT/BT combination (76.7%). Median duration of first line therapy was 4 mo (range 0.2-20.0). Progression to the first-line CT +/- bevacizumab was reported in 51.1% pts with a median time to progression (TTP) of 4.7 mo (range 0.8-19.0) in the whole group, being similar in pts with TN in and PT and PT/M1 (4.4 mo), and higher in pts with TN in M1 (7.1 mo), no statistically significant difference (p=0.38). A second-line therapy was reported in 57.3% pts and the most frequent therapies were CT (78.7%) (eribulin 33.9%, capecitabine 22.0%, platinum-based 22.0%) and CT/BT (12.0%) (CT-containing bevacizumab 77.8%). Median duration of second-line therapy was 3 mo (range 0.03-15.8) and PD has been reported in 80.0% pts. Third-line therapy was reported in 35.9% pts of this subset. Conclusion: In this subset of pts with TN ABC due to recurrent disease, lung, lymph nodes and bone are the most frequent metastatic locations. The main first- and second-line therapies were CT in monotherapy. Progression to the first-line conventional therapy (CT +/- bevacizumab) was reported in 51.1% pts with a median TTP of 4.7 mo (range 0.8-19.0) in the whole group, being similar in pts with TN in PT and PT/M1 (4.4 mo), and higher in pts with TN in M1 (7.1 mo), no statistically significant difference. 36% of the initial subset of pts reported to be treated in the third-line setting. Pts with TN only in M1 seem to have a longer time to progression from EBC.

Citation Format: Carlos Jara, César A. Rodríguez, Isabel Alvarez, Catalina Falo, Purificación Martínez, Raquel Andrés, Josefina Cruz, Marta Mori, Encarna Adrover, Ariadna Tibau, Silvia Antolin, Mireia Margeli, Jose L. Alonso, Bella I. Pajares, M. Carmen Camara, J. Jose Miralles, Susana Bezares, Federico Rojo, Sara López-Tarruella, Angel Guerrero- Zotano. Geicam/2014-03 (RegisTEM): A prospective registry of unresectable locally advanced or metastatic breast cancer: Characteristics of a subset of patients with triple negative subtype [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS7-25.