[Tumor regression grade for prognosis of patients with colorectal cancer liver metastasis undergoing conversion therapy].

Objective: To explore the prognostic significance of tumor regression grade (TRG) for patients with colorectal liver metastasis (CRLM) who underwent liver resection after conversion therapy. Methods: A retrospective cohort of 156 CRLM patients who received conversion therapy and subsequent liver resection at Chenzhou First People's Hospital between 2018 and 2024 was analyzed. The conversion therapy regimen was mainly FOLFOX, FOLFIRI, or combined with targeted therapy. Preoperative and postoperative evaluations were conducted using the Response Evaluation Criteria in Solid Tumors (RECIST) and TRG. Patients were further divided into the good response group (TRG 1-2) and the poor response group (TRG 3-4) based on the degree of liver metastasis regression. The primary outcome measure was the 5-year overall survival rate (OS), and independent influencing factors of OS were analyzed using the multivariate Cox regression model. Results: A total of 74 patients were classified as good responders (good response group), and 82 patients were classified as poor responders (poor response group). The median follow-up duration for all patients was 38 (range, 2-76) months. The 5-year OS rate was 38.4%, and the 5-year recurrence-free survival rate was 19.7%.The 5-year OS and 5-year recurrence-free survival rate in the good response group were significantly superior to those in the poor response group (all P<0.001). Multivariate Cox regression analysis showed that tumor regression grade (TRG) 3-4 (HR=4.68, 95%CI: 2.49-8.78, P<0.001) was an independent risk factor for OS. A decline in serum carcinoembryonic antigen (CEA) level by more than 50% (HR=0.68, 95%CI: 0.47-0.97, P=0.027)was an independent protective factor, whereas the therapeutic response evaluated by the RECIST criteria was not an independent influencing factor. Conclusion: Postoperative pathological TRG is more accurate than the preoperative RECIST criteria in predicting the prognosis of patients with CRLM after conversion therapy.