Targeted Therapy for Gastric Cancer

For patients with advanced gastric cancer, traditional double or triplet cytotoxic chemotherapy regimens result in a median survival of 9-11 months. As combination therapy is associated with increased survival, but also increased toxicity in a patient population whose performance status often compromised by their malignancy, development of more effective and less toxic treatment choices is mandated. Emerging data from gene expression profiling suggests that differences in pathological appearance and clinical behavior may be due the presence of unique molecular phenotypes. Characterization of the gastric cancer genomic landscape reveals the presence of multiple alterations in expression of receptor tyrosine kinases, which in conjunction with their ligands and downstream effector molecules represent potentially druggable pathways for future drug development. Treatment of HER2 positive gastric cancer with trastuzumab has led to significant gains in overall survival, and further manipulation of this pathway using the novel anti-HER2 directed agents pertuzumab and T-DM1 in addition to dual EGFR/HER2 blockade with lapatinib may yield positive results. In contrast, targeting of the EGFR pathway in combination with chemotherapy in unselected patients has not been fruitful to date, with no significant gains over standard chemotherapy yet demonstrated. Similarly, use of the anti-angiogenic monoclonal antibody bevacizumab was not successful in a large global randomized trial; however intriguing regional variations were seen with respect to efficacy of this drug, leading to calls for a second, regionally stratified study. Careful selection of patient subsets will become a key factor in future clinical trials, as novel targeted agents such as those targeting the MET/HGF and FGFR axes move forward into clinical development. It is hoped that treatment of patients in such molecularly defined groups is will lead to significant gains in survival compared to current treatment paradigms.