Pertuzumab plus trastuzumab and chemotherapy for Japanese patients with HER2-positive metastatic gastric or gastroesophageal junction cancer: a subgroup analysis of the JACOB trial

Background The phase III JACOB trial (NCT01774786) compared the efficacy and safety of pertuzumab and trastuzumab plus chemotherapy with placebo and trastuzumab plus chemotherapy in patients with previously untreated human epidermal growth factor receptor 2 (HER2)-positive metastatic gastric or gastroesophageal junction cancer. We conducted a subgroup analysis in Japanese patients. Methods Patients were randomized 1:1 to pertuzumab 840 mg or placebo, plus trastuzumab (loading dose, 8 mg/kg; maintenance dose, 6 mg/kg) and chemotherapy (cisplatin 80 mg/m 2 , and capecitabine 1000 mg/m 2 twice daily for 28 doses or 5-fluorouracil 800 mg/m 2 every 24 h for 120 h), every 3 weeks. Continuation of chemotherapy after 6 cycles was at the discretion of the patient and the treating physician. Results A total of 40 Japanese patients were included in each arm. Median overall survival was 22.0 months (95% confidence interval [CI] 13.8–not evaluable) and 15.6 months (95% CI 9.7–19.2) in the pertuzumab and placebo arms, respectively (hazard ratio [HR] 0.64 [95% CI 0.37–1.10]). Median progression-free survival was 12.4 months (95% CI 6.1–14.1) in the pertuzumab arm and 6.3 months (95% CI 4.3–8.1) in the placebo arm (HR 0.50 [95% CI 0.30–0.82]). Grade ≥ 3 adverse events and serious adverse events were more frequent in the pertuzumab arm than the placebo arm. Conclusions Results from this subgroup analysis of the JACOB trial suggest similar efficacy of pertuzumab in Japanese patients and patients in the overall population, encouraging continued investigation of new agents for gastric cancer in Japanese patients.