Jiyang Li, Tengyu Zeng, Xianqiang Xie, Dongsheng Li, Kejin Yan, Hongliang Zhu
Our study found that MA was an independent adverse prognostic factor in stage III CRC when patients were receiving standard single-modality chemotherapy. However, among stage III rectal cancer patients treated with combined preoperative and postoperative chemotherapy, the prognostic disadvantage of MA was eliminated.
BACKGROUND: The prognostic significance of mucinous adenocarcinoma (MA) compared to conventional adenocarcinoma (AC) in colorectal cancer (CRC) remains controversial, particularly in the context of modern treatment. This study aims to clarify the independent prognostic value of MA in the contemporary treatment model through large-sample analysis, in order to provide more evidence for risk stratification and treatment decision-making for MA patients.
METHODS: This retrospective cohort study analyzed patients with stage I-III CRC who underwent curative resection between 2010 and 2022 from the Surveillance, Epidemiology, and End Results (SEER) database. Overall survival (OS) and cancer-specific survival (CSS) were compared between MA and AC groups. Multivariable Cox regression and subgroup analyses stratified by pathological stage, tumor site, and chemotherapy modality were performed. Propensity score matching (PSM) was applied to stage III cohorts to control for confounding.
RESULTS: Among 69,335 patients with CRC, MA was associated with significantly worse OS and CSS before subgroup analysis (P<0.001). However, multivariable analysis revealed that MA was an independent adverse prognostic factor exclusively in stage III both colon and rectal cancer (all P<0.05), but not in stages I or II. Treatment-stratified analysis in stage III patients revealed that the prognostic impact of MA was highly chemotherapy modality-dependent. In stage III colon and rectal cancer patients who did not receive chemotherapy, MA and AC showed comparable OS and CSS. Conversely, among those who received preoperative or postoperative chemotherapy, MA remained an independent poor prognostic factor (all P<0.05), indicating reduced benefit from chemotherapy compared to AC. Notably, in stage III rectal cancer patients who received combined preoperative and postoperative chemotherapy, the survival disadvantage of MA disappeared. PSM analysis confirmed the robustness of these findings.
CONCLUSIONS: Our study found that MA was an independent adverse prognostic factor in stage III CRC when patients were receiving standard single-modality chemotherapy. However, among stage III rectal cancer patients treated with combined preoperative and postoperative chemotherapy, the prognostic disadvantage of MA was eliminated.