2264 - Differences In Pathological Responses between Primary Tumor and Lymph Nodes after Neoadjuvant Therapy In Locally Advanced Rectal Cancer: A Meta-Analysis
Presenter(s)
Y. Wang1,2, L. L. Xiao1, and F. P. Wu1; 1Department of Radiation Oncology, The Fourth Hospital of Hebei Medical University, Shijiazhuang, China, 2Department of Cancer Center,Affiliated Hospital of Hebei University of Engineering, Handan, China
Purpose/Objective(s): To evaluate the differences in pathological responses between the primary tumor and positive lymph nodes after neoadjuvant therapy (NAT) in locally advanced rectal cancer (LARC), and to assess the influence of various neoadjuvant treatment strategies on the degree of tumor regression.
Materials/Methods: Relevant studies were searched in PubMed, Embase, the Cochrane Library, and Web of Science databases. The quality of randomized controlled trials (RCTs) was assessed using the Cochrane Risk of Bias Tool (RoB 2.0), while single-arm studies were evaluated with the Methodological Index for Non-Randomized Studies (MINORS). Outcome measures, including pathological complete response of the primary tumor (ypT0), pathological complete response of lymph nodes (ypN0), and major pathological response (MPR) of the primary tumor, were analyzed using RevMan 5.4 software. Subgroup analyses were conducted based on whether immune checkpoint inhibitors (ICIs) were combined with NAT, different treatment modalities, and radiotherapy regimens.
Results: A total of 17 studies (15 RCTs and 2 single-arm studies) involving 5,105 patients with LARC were included in the analysis. After NAT, the ypN0 rate was significantly higher than both the ypT0 rate (OR = 10.14, 95% CI 8.80–11.69, P < 0.0001) and the MPR rate of the primary tumor (OR = 3.12, 95% CI 2.40–4.08, P < 0.0001). Subgroup analyses revealed that the ypN0 rate remained markedly higher than both the ypT0 rate and the MPR rate, regardless of whether ICIs were incorporated into NAT, whether patients received total neoadjuvant therapy (TNT) or conventional neoadjuvant chemoradiotherapy (NCRT), or whether long-course chemoradiotherapy (LCRT) or short-course radiotherapy (SCRT) regimens were employed. Additionally, combining ICIs with NAT markedly improved the ypT0 rate (OR = 2.49, 95% CI 1.57–3.95, P < 0.0001) and the MPR rate (OR = 2.16, 95% CI 1.25–3.74, P = 0.006) compared with non-ICIs, but no significant difference was observed in the ypN0 rate. Patients undergoing TNT had a higher ypT0 rate (OR = 1.88, 95% CI 1.41–2.51, P < 0.0001) and ypN0 rate (OR = 1.39, 95% CI 1.02–1.90, P = 0.04) compared with those receiving NCRT.
Conclusion: After NAT for rectal cancer, positive lymph nodes appear more likely to achieve a pathological response than primary tumors. Furthermore, the combination with ICIs or the adoption of TNT can further enhance tumor regression.