Clinical utility of SERUM extracelullar domain of HER2 receptor (ECD) in HER2-positive breast cancer.

• DOI: 10.1200/jco.2019.37.15_suppl.e12086
• Publication Date: 2019-05-27T15:54:06Z
• Authors: Ariadna Gasol Cudós; Serafin Morales M...; Joel Veas Rodriguez; Carles Canosa Mor...; Jordi Melé Olivé; Antonia Salud
• Keywords: 03 medical and health sciences; 0302 clinical medicine; 3. Good health

e12086 Background: Although ECD expression was validated as tumor marker years ago, it is not used in daily clinical practice even if a prognostic value was demonstrated in some trials. Methods: In our single institution, during January 2013-2019, ECD was analyzed in a series of HER2 positive breast cancer patients; 71 in early or locally-advanced and 45 in metastatic setting. Results: In the metastatic cohort, median ECD expression was of 28 ng/ml (6,5-350), thus 10 (22%) patients had lower levels than threshold of 15ng/ml. No correlation was found between ECD expression and other clinicopathological variables. No association was found with overall survival however in patients with metastases at diagnosis higher ECD expression was correlated with a short overall survival (25 vs 54 months). Higher levels of ECD decreased according to good response to treatment. Median ECD expression was of 12ng/ml (3,6-97) in non-metastatic setting, however only 11 (15%) patients had elevated levels ( > 15ng/ml). Estrogen receptor and ki67 expression were not correlated with ECD levels. Median ECD expression in tumors > 5cm was 21,87 ng/ml versus 12ng/ml in smaller tumors (p = 0,006); in nodal involvement median ECD was 16,77 ng/ml versus 12,05 without affectation (p = 0,09). Patients with ECD higher than 10 ng/ml had a 55% pathologic complete response (pCR) versus 25% if less than 10ng/ml (OR 3.68, p = 0.027). Interestingly, none of tumors > 5cm and ECD < 10ng/ml achieved a pCR. Conclusions: Higher levels of ECD were observed in the metastatic setting and their decreased levels during treatment was correlated with response. In early and locally-advanced setting higher levels were found in larger tumors; and also these tumors had better response than lower levels of ECD. ECD could be used as a monitoring tool in the metastatic scenario and as a predictive factor of response in the neoadjuvant setting, specifically in tumors > 5cm.