ERBB2 and gastroesophageal junction adenocarcinoma: In preclinical studies, although pertuzumab plus trastuzumab enhanced antitumor activity [51], the addition of pertuzumab to standard therapy failed to significantly improve the survival of patients with HER2-positive metastatic G/GEJ adenocarcinoma in the first-line placebo-controlled JACOB trial (mOS 17.5 vs. 14.2 months; P = 0.056) [52].