Background: Almost all adjuvant chemotherapy regimens for gastric cancer recommended by guidelines are fluorouracil (5-FU) based, and 5-FU-based adjuvant chemotherapy plays an important role in reducing the recurrence of gastric cancer after surgery. However, the effect of mismatch repair (MMR) status on survival after 5-FU-based adjuvant chemotherapy in patients with gastric cancer remains controversial.
Materials and methods: We prospectively included patients with gastric cancer who underwent radical gastrectomy between March 14, 2017 and September 30, 2021. The included patients received 5-FU-based adjuvant chemotherapy or surgery alone. The MMR status of patients was divided into MMR proficient (pMMR) and MMR defective (dMMR) according to four MMR proteins. Peripheral blood was collected for systemic inflammation analysis. The main purpose of this study was to analyze the effect of MMR status on survival after 5-FU-based adjuvant chemotherapy in patients with gastric cancer. We also analyzed the differences in systemic inflammation levels in different MMR status and their impact on survival.
Results: A total of 479 patients were enrolled, with a median follow-up period of time was 36 months. In the surgery alone group, dMMR gastric cancer had better disease-free survival (DFS) (hazard ratio [HR] = 4.33, 95% confidence interval [CI] 1.25-15.02, p = 0.02) than pMMR, and in the adjuvant chemotherapy group, there was no significant difference in DFS (HR = 1.16, 95% CI 0.65-2.07, p = 0.61) between dMMR and pMMR gastric cancer. The same results were seen for overall survival (OS). In addition, the result show that in the dMMR group, there was no difference in DFS (HR = 1.62, 95% CI 0.46-5.77, p = 0.45) between patients receiving adjuvant chemotherapy and those receiving surgery alone. In the pMMR group, the DFS values (HR = 0.59, 95%CI 0.35-0.99, p = 0.04) of patients receiving adjuvant chemotherapy were better than those of patients receiving surgery alone, and the same results were observed for OS. In addition, among pMMR patients, patients with a low platelet lymphocyte ratio (PLR) who received 5-FU adjuvant chemotherapy and those with a low neutrophil lymphocyte ratio (NLR) and systemic immune-inflammation index (SII) who received surgery alone had better DFS and OS.
Conclusion: To our knowledge, this is the first prospective study to specifically explore the correlation between MMR and survival of patients with gastric cancer after 5-FU-based adjuvant chemotherapy. The results showed that gastric cancer patients with pMMR can benefit from 5-FU-based adjuvant chemotherapy, but those with dMMR cannot. Among pMMR patients, lower PLR and SII values with surgery alone and lower NLRs in those receiving 5-FU-based adjuvant chemotherapy were associated with higher DFS and OS.
Keywords: 5-FU-based adjuvant chemotherapy; Gastric cancer; Mismatch repair; Survival; Systemic inflammation.
© 2023. Japanese Society of Gastroenterology.