P-232 - Characterization of serum HER2 ECD level in patients with metastatic colorectal cancer

Date 04 July 2015
Event WorldGI 2015
Session Posters
Topics Colon Cancer
Rectal Cancer
Translational Research
Presenter H. Taniguchi
Citation Annals of Oncology (2015) 26 (suppl_4): 1-100. 10.1093/annonc/mdv233
Authors H. Taniguchi1, H. Hasegawa2, T. Masuishi1, Y. Narita1, A. Komori1, S. Kadowaki1, T. Ura3, K. Muro1
  • 1Aichi Cancer Center Hospital, Nagoya/JP
  • 2Osaka National Hospital, Osaka/JP
  • 3Aichi Cancer Center, Nagoya/JP

Abstract

Introduction

The overexpression of human epidermal growth factor receptor (HER) 2 occurs in approximately 20% of breast/gastric and 5% of colorectal cancers. Moreover, activation of the HER2 pathway has been reported to be one of the mechanisms of primary or acquired resistance to anti-EGFFR antibodies in RAS wild-type metastatic colorectal cancer (mCRC). The serum level of the HER2 extracellular domain (ECD) is used as a tumor marker in HER2 positive gastric and breast cancers. However, little is known about HER2 ECD levels or characterization in mCRC patients.

Methods

We prospectively analyzed consecutive mCRC patients receiving palliative chemotherapy in our hospital. The HER2 ECD positivity was defined as a serum level 3 15.2 ng/mL, based on the manufacturer's recommended cutoff value.

Results

A total of 181 patients were enrolled in this study. The patients’ characteristics were as follows: males/females (57%/43%), median age (range): 65 (24-93) years, primary site: right colon/left colon/rectum (23%/30%/44%), RAS status: wild-type/RAS mutant/BRAF mutant/unknown (56%/34%/4%/6%). The positive rates of HER2 ECD, CEA, and CA19-9 were 25.4, 76.8, and 49.7%, respectively. The HER2 ECD level showed a linear relationship with the CEA level (correlation coefficient: 0.677), but was not associated gender, primary site, and number of metastatic sites. According to the association with the RAS status, serum levels of HER2 ECD in RAS wild-type patients were slightly higher than those in RAS mutant patients (positive rates: 31 vs. 18%, respectively). Moreover, in RAS wild-type patients, those with resistance to anti-EGFR antibody within 1 year showed a higher positive rate of HER2 ECD than the others (56 vs. 26%, respectively; p = 0.0682).

Conclusion

A non-negligible number of mCRC patients showed positive serum levels of HER2 ECD. HER2 ECD may be associated with the tumor burden and acquired resistance to anti-EGFR therapy, but further studies are necessary to determine the clinical utility of HER2 ECD.