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Re-evaluation of HER2 status in patients with HER2-positive advanced or recurrent gastric cancer refractory to trastuzumab (KSCC1604).

Saeki, Hiroshi; Oki, Eiji; Kashiwada, Tomomi; Arigami, Takaaki; Makiyama, Akitaka; Iwatsuki, Masaaki; Narita, Yukiya; Satake, Hironaga; Matsuda, Yoshiko; Sonoda, Hideto; Shimokawa, Mototsugu; Maehara, Yoshihiko.
Eur J Cancer; 105: 41-49, 2018 12.
Artigo em Inglês | MEDLINE | ID: mdl-30391779

BACKGROUND:

Anti-HER2 therapy has not demonstrated a survival advantage in the second-line setting of patients with HER2-positive gastric cancer. We conducted this study to assess changes in HER2 status and to identify possible biomarkers for acquired resistance after the use of trastuzumab as the first-line therapy. PATIENTS AND

METHODS:

Patients with advanced or recurrent HER2-positive gastric adenocarcinoma who were diagnosed with progressive disease after the first-line trastuzumab-based therapy and developed pathologically confirmed adenocarcinoma within 3 months after completion of trastuzumab-based therapy were enrolled in this study. We collected re-biopsied samples from the HER2-positive patients who had developed resistance to trastuzumab and re-evaluated their HER2 status. Amplification of EGFR and c-met, as well as PIK3CA mutation, were comparatively analysed when samples were available.

RESULTS:

Among 33 eligible patients, loss of HER2 was identified in 20 patients (60.6%) with refractory disease. Immunohistochemistry showed that the rate of HER2 overexpression was greatly reduced after therapy (pre-HER2 3+ 24 [72.7%] vs. post-HER2 3+ 13 [39.4%]). We found that the use of fixatives other than 10% neutral buffered formalin significantly reduced the HER2-positive rate. EGFR amplification, c-met amplification and PIK3CA mutation before and after trastuzumab-based therapy were observed in 10.3% and 3.8%, 17.9% and 4.2% and 4.0% and 4.2% of cases, respectively.

CONCLUSION:

Re-evaluation of HER2 status is needed to determine the appropriate use of anti-HER2-targeted therapy after disease progression. Our results also highlight the importance of formalin fixation conditions for HER2 testing.
Selo DaSilva