Limited data are available regarding the optimal regimen to add to trastuzumab-based therapy in metastatic patients with HER2-positive gastric cancer. In our study, we found that CFT and OCT therapies had similar efficacy and safety. Trastuzumab-based therapies are used as standard in the first series in HER2-positive metastatic gastric cancer. Cisplatin-based therapies have been used to treat metastatic gastric cancer for a long time. A multicenter randomized phase 3 study by Lee et al. showed that oxaliplatin was non-inferior to cisplatin
7. Yamada et al.
8 found that oxaliplatin and cisplatin had similar efficacy when used in combination with S1 in patients with metastatic gastric cancer, but that oxaliplatin-based therapy was relatively less toxic.
Similarly, in a phase 2 study, Kim et al. detected that cisplatin and oxaliplatin-based treatments had similar efficacy and safety when used weekly with docetaxel in advanced gastric cancer patients9. However, in a phase 2 study published by Hironaka et al.10, has been found that oxaliplatin combined with S1 was more effective than cisplatin in metastatic gastric cancer. In this research, the median OS was 18.4 months in the S-1 plus leucovorin and oxaliplatin group and 12.6 months in the S-1 plus cisplatin group. These results were supported in a phase 3 study recently published by Kang et al.11 the researchers have been found that using oxaliplatin in combination with S1 in the Asian population significantly improved survival to cisplatin and the response ratio from 50% to 73%. In the literature, different results were obtained in studies comparing oxaliplatin and cisplatin in advanced gastric cancer patients. In our results, although cisplatin-based therapy had similar efficacy to oxaliplatin-based therapy in HER2-positive gastric cancer patients, a non-significant survival-enhancing trend was observed in cisplatin-based therapy. Our study's small number of patients may have caused a bias effect. But, these contradictory results in the literature can also be explained by the different efficacy levels of drugs in different races. In addition, HER2-positive gastric cancer may have different properties in terms of platinum sensitivity. An article that investigated the cell growth inhibi-tory effect of trastuzumab in HER2-positive gastric SNU-216 cancer line discovered to a synergistic effect when using together trastuzumab with cisplatin12.
In a meta-analysis published by Zhang et al.13, oxaliplatin was found to have a better profile in terms of safety, together with it was superior to cisplatin in patients with metastatic gastric cancer. Furthermore, compared to cisplatin-based treatment, oxaliplatin-based therapy has been detected that minimized grades 3-4 of anemia, leukopenia, and febrile neutropenia.
However, oxaliplatin-based treatment significantly had been increased tiredness, sensory neuropathy, diarrhea, and thrombocytopenia. Another meta-analysis found that oxaliplatin-based therapy had lower toxicity and better tolerance, particularly in older patients and when administered in two-drug, bi-weekly regimens in metastatic gastric cancer14. In another meta-analysis published by Huang et al.15, although oxaliplatin-based treatment has similar efficacy with cisplatin-based treatment, toxicities other than sensorineural neuropathy and thrombocytopenia were less detected. In our study, hematological and non-hematological toxicities were observed at similar rates in the patients of the two treatment groups. Due to a low number of patients, the toxicity difference between the treatment groups may not have emerged.
Our research has a few limitations. Because this was an uncommon tumor, the number of patients in our research was modest. Some data were missing due to the study's retrospective nature. There was a heterogeneous distribution for some characteristics in the treatment groups.
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