Downstaging Effect Rather than the Full Intended Cycles of Perioperative Chemotherapy Determines the Value of Adjuvant Chemotherapy in Gastric Cancer.

Background: Perioperative chemotherapy is the standard treatment modality for locally advanced gastric cancer. However, the efficacy and indication of adjuvant chemotherapy in patients who have already received neoadjuvant chemotherapy remain unclear. This study aims to explore the association between adjuvant chemotherapy with patient prognosis in those who have received neoadjuvant chemotherapy plus D2 gastrectomy in a real-world setting, and whether this association is affected by the duration of neoadjuvant treatment.

Patients and methods: A total of 174 patients with cT3-4N+ gastric cancer who had received neoadjuvant chemotherapy plus D2 radical gastrectomy were included in the study. Kaplan-Meier curves and log-rank tests were used to assess and compare the survival outcomes between patients who received adjuvant therapy and those who did not.

Results: Patients who were younger age, had a lower American Society of Anesthesiologists (ASA) grade, did not experience postoperative complication, and received fewer than six cycles of neoadjuvant chemotherapy were more likely to receive adjuvant chemotherapy, rather than those with advanced ypTNM stage or poor tumor regression grade. Patients who received adjuvant therapy had a better overall survival (OS) (2-year OS rate 86.2% versus 64.1%, p = 0.002). Adjuvant therapy was associated with longer survival in patients who remained ypTNM stage III despite receiving at least six cycles of neoadjuvant chemotherapy. However, there was no significant longer survival observed in patients with ypTNM stages 0-II receiving adjuvant chemotherapy, even when they received less than six cycles of neoadjuvant chemotherapy.

Conclusions: Patients with locally advanced gastric cancer may still need adjuvant chemotherapy, even after receiving neoadjuvant chemotherapy. The value of adjuvant chemotherapy after neoadjuvant chemotherapy depends more on the actual downstaging effect achieved after neoadjuvant chemotherapy, rather than the completion of "full intended" cycles of perioperative treatment.