We planned this study to investigate the efficacy and safety of XELOX (capecitabine and oxaliplatin) plus lapatinib treatment in HER2-positive gastric cancer patients with liver metastasis.
Gastric cancer is the leading cause of cancer death worldwide with the incidence of 18.9/100,000 per year and the mortality rate of 14.7/100,000 per year \[1\] and is the most common malignancy in Korea\[2\]. Metastatic gastric cancer remains a therapeutic challenge for medical oncologists due to poor prognosis. Several randomized phase III trials comparing combination chemotherapy such as 5-fluorouracil (5-FU), doxorubicin, and mitomycin (FAM), or 5-FU, doxorubicin, and high-dose methotrexate (FAMTX) with best supportive care have demonstrated significantly prolonged overall survival (8 - 10 months) for chemotherapy group as compared to best supportive care alone (3 - 5 months)\[3, 4\]. In quest of a novel therapeutic target for gastric cancer, HER2 overexpression has been tested and was reported in 6-35% of stomach and gastroesophageal tumors \[5\]. Trastuzumab, a humanized monoclonal antibody which selectively targets HER2, has shown survival benefit in patients with HER2(+) metastatic breast cancer \[6-8\]. The ToGA trial is the first randomized, prospective, multicenter, phase III trial to study the efficacy and safety of trastuzumab in HER2(+) GC \[9\]. Of 3,807 tumor samples screened for Her2 status, 22.1% were Her2 positive and 594 patients were randomized to receive chemotherapy alone or chemotherapy + trastuzumab. The ToGA trial demonstrated a significant survival benefit in the transtuzumab +chemotherapy when compared with chemotherapy alone arm: 13.5 vs. 11.1 months, respectively (p=0.0048; HR 0.74; 95% CI 0.60, 0.91). ORR was 47.3% in the trastuzumab + 5-FU/CDDP (or capecitabine/CDDP) arm and 34.5% in the chemotherapy alone arm (p=0.0017). The ToGA trial is the first phase III trial to demonstrate survival benefit from molecularly targeted agent in gastric cancer. Of note, 70 - 80% of patients HER2 overexpressing breast cancer do not respond to trastuzumab due to either primary or acquired resistance. One of the important mechanisms for trastuzumab resistance is the accumulation of truncated forms of the HER2 receptor which lack the extracellular trastuzumab-binding domain (Figure 2). P95HER2, an amino terminally truncated carboxyl terminal fragments of HER2, is frequently found in HER2(+) breast cancer cell lines and tumor specimens (\~20%)\[11\]. Intriguingly, recent study showed that p95HER2 (+) breast cancer cells were resistant to trastuzumab but remained sensitive to the antiproliferative effects of the tyrosine kinase inhibitor lapatinib, both in vitro and in vivo\[11\]. In addition, patients with p95HER2(+)breast cancer were resistant to trastuzumab with significantly lower response rate when compared with full-length HER2(+) breast cancer (11.1% vs 51.4%, respectively; P = 0.029). We have surveyed the incidence of p95HER2 expression in fresh frozen tissues from gastric cancer and found that \> 60% of HER2 (3+) GC demonstrated p95HER2. Hence, the role of lapatinib may be more promising than trastuzumab in GC HER2(+) patients with truncation.
Study Type
INTERVENTIONAL
Allocation
NA
Purpose
TREATMENT
Masking
NONE
Enrollment
32
lapatinib 1250mg qd daily up to 8 cycles (3 weeks \* 8 cycles = 24 weeks)
Samsung Medical Center
Seoul, Korea, South Korea
complete resection rate (R0 resection rate) (defined as no macroscopic or microscopic residual tumor).
Time frame: after surgery, up to 3weeks
response rate based on RECIST 1.1
Time frame: every 3 cycles, up to 24weeks
disease-free survival
Time frame: after surgery, every 3 months
progression-free survival
from date of study enrollment until the date of first documented progression or date of death from any cause, whichever came first
Time frame: every 3 cycles for 6 months and ten every 3 months up to 3 years
safety and toxicity based on NCI CTCAE ver. 4.0
Number of participants with adverse events
Time frame: every cycles, up to 24 weeks
Exploratory biomarker analysis
change in circulating tumor cells, HER2 positivity in primary and metastatic tumors, Receptor tyrosine kinase activation profiling including total HER1, HER2, HER3, phosphorylated HER1, HER2, HER3 - Prometheus, USA, Correlation between response rate and p95HER2 (truncated HER2)) Correlation between RR and RNA sequencing (all available tissue specimens)
Time frame: every 3 cycles, up to 24weeks
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