5-Fu Plus Epirubicin is Superior to Standard 5-FU Plus Cisplatin and Epirubicin in the Neoadjuvant Gastric Cancer Spheroid Model

Introduction: 5-fluorouracil combined with Cisplatin and Epirubicin (FCE) is a well-accepted standard therapy in neoadjuvant gastric cancer. However, a number of side effects are observed for this combination therapy in a large portion of the patient cohorts. This raises the question whether a different backbone using Oxaliplatin or Irinotecan or even a doublet combination is equally effective as the FCE treatment regimen. Methods: The combination therapies 5-FU plus either Cisplatin, Oxaliplatin or Irinotecan (FC, FO and FI), with or without the addition of Epirubicin (FCE, FOE and FIE), as well as Epirubicin as monotherapy and in combination with 5-FU (FE) were analysed in a three-dimensional multicellular tumor spheroid model derived from patient tumor samples. Surgical material or tissue biopsies of 22 gastric cancer patient tumors were processed in vitro for the direct formation of multicellular tumor spheroids. After 48h, treatment with the intended chemotherapeutic drug combinations was conducted. Treatment efficacy was measured after further 48h using the ATP assay and expressed as residual metabolic activity in per cent of solvent control. For Statistical analysis, Kolmogorov-Smirnov test for normal distribution and Mann-Whitney-U test was performed. Results: Of the three doublet combination therapies FC, FO and FI, the most effective treatment FC statistically showed a tendency to be superior to FO (p = 0,067; 35,87% vs. 45,38% residual metabolic activity) and was significantly superior to FI (p = 0,002; 53,29% residual metabolic activity). When adding Epirubicin to each of the combinations, the three treatments FCE, FOE and FIE were equally effective (29,34%, 29,28% and 27,64% residual metabolic activity, respectively), suggesting that Epirubicin has the strongest effect on the therapeutic efficacy of the triplet combinations. Three of the patient tumor samples were additionally tested in this respect and revealed a significantly lower efficacy of Epirubicin alone in comparison to the other Epirubicin-containing regimens (p = 0,002). A comparable therapeutic efficacy to the triplet combinations FCE, FOE and FIE was achieved with the FE doublet combination (patient #1: 20,37% FCE, FOE, FIE vs. 23,68% FE; patient #2: 3,83% FCE, FOE, FIE vs. 6,91% FE and patient #3: 15,25% FCE, FOE, FIE vs. 24,75% FE, respectively). Conclusion: The triplet combinations with Epirubicin all had similar therapeutic efficacies in vitro although their corresponding backbones without Epirubicin show different efficacies. The hypothesis that Epirubicin has the largest impact on the overall efficacy of the regimen was confirmed for three patient samples by the efficacy of the doublet combination FE which was as effective as each of the Epirubicin triplet combinations. As treatment regimens with less drug components potentially have fewer side effects for the patients, especially when removing a platinum component, gastric cancer patients might benefit from the FE combination treatment.