Impact of Neoadjuvant Chemotherapy on Prognosis of Patients with Mucinous Gastric Adenocarcinoma: A Propensity Score Matching Study

BACKGROUND: Mucinous gastric adenocarcinoma (MGC) is a rare, aggressive malignancy. This study aimed to explore whether MGC is associated with poorer survival compared with nonmucinous gastric adenocarcinoma (NMGC) and to further investigate the potential impact of neoadjuvant chemotherapy (NAC) on MGC by assessing overall survival (OS), tumor regression grade (TRG), and histological subtypes. METHODS: A retrospective analysis was conducted on 492 patients with MGC and 7945 patients with NMGC undergoing resection at Zhejiang Cancer Hospital (2014-2023). Patients were categorized into neoadjuvant and surgery groups. MGC was further classified as pure (≥ 80%) or mixed (< 80%). OS was analyzed using Kaplan-Meier and Cox regression, with propensity score matching (PSM) for adjustment. RESULTS: After PSM, OS did not differ between MGC and NMGC. Patients with MGC receiving NAC had significantly worse OS than those undergoing surgery, with NAC as an independent risk factor. TRG analysis showed a markedly lower proportion of responders (TRG 0-1) in MGC than NMGC, indicating reduced chemosensitivity. Among subtypes, NAC remained an adverse factor in pure MGC, while mixed MGC showed no significant difference after PSM. CONCLUSIONS: MGC exhibits poor pathological response and no survival benefit from NAC, supporting upfront surgery as the preferred approach. TRG findings highlight intrinsic chemoresistance, particularly in pure MGC, underscoring the need for histology-based individualized strategies.