新辅助免疫治疗在局部晚期直肠癌中应用循证证据

Evidence-based application of neoadjuvant immunotherapy in locally advanced rectal cancer

错配修复功能缺陷(deficient mismatch repair,dMMR)是目前公认的预测免疫检查点抑制剂(immune checkpoint inhibitors,ICIs)疗效的生物标志物,国内外指南已推荐dMMR实体瘤患者一线治疗选择免疫治疗。在直肠癌中,仅5%患者为dMMR/高度微卫星不稳定(microsatellite instability-high,MSI-H),绝大多数为“免疫沙漠型”或错配修复功能完整(mismatch repair proficient,pMMR)/微卫星稳定(microsatellite stabilization,MSS),即对ICIs反应欠佳。因此免疫药物与新辅助放化疗的协同作用是近些年基础和临床研究的热点,并且有较多Ⅱ/Ⅲ期免疫全新辅助治疗(immuno-total neoadjuvant therapy,iTNT)相关临床试验涌现,局部进展期直肠癌(locally advanced rectal cancer,LARC)管理模式也开始进入非手术治疗时代。dMMR/MSI-H型LARC患者新辅助免疫疗法效果显著,有望让患者在后续治疗中豁免手术和放化疗从而选择观察等待策略;对于pMMR/MSS型LARC,目前初步认定ICIs从初始作为后线姑息方案前移到一线选择策略以及继续开展大型临床试验。但iTNT在LARC中应用最佳模式尚无定论,但短程放疗序贯新辅助化疗联合免疫药物可能获得良好短期疗效。寻找其它新的生物标志物,可能会鉴定出部分对iTNT敏感的pMMR/MSS型患者(尤其是低位直肠癌)。未来LARC治疗策略需结合患者临床复发危险度分层和器官保留意愿两方面考虑,实现分层精准治疗。本文将对LARC中iTNT的相关研究背景、基础和临床研究进展以及存在问题等进行综述。

Deficient mismatch repair(dMMR)is currently recognized as a biomarker for predicting the efficacy of immune checkpoint inhibitors(ICIs),and domestic and foreign guidelines recommend first-line immunotherapy for patients with solid dMMR tumors.For rectal cancer,only 5%of patients are classified as dMMR/microsatellite instability-high(MSI-H),and most have“immune desert type”or mismatch repair proficient(pMMR)/microsatellite stabilization(MSS)diseases,which respond poorly to ICIs.Therefore,recently,the synergistic effect of immune drugs and neoadjuvant chemoradiotherapy has been the focus of basic and clinical research.An increasing number of clinical trials of phaseⅡ/Ⅲimmuno-total neoadjuvant therapy(iTNT)have emerged,and the management of locally advanced rectal cancer(LARC)has begun to enter the non-operative treatment era.Furthermore,an increasing number of studies support the efficacy of neoadjuvant immunotherapy in patients with dMMR/MSI-H LARC,which exempts such patients from surgery and chemoradiotherapy as follow-up treatment and results in a pivot in the treatment paradigm of a watch-and-wait strategy.Regarding the LARC with pMMR/MSS,the preliminary iTNT findings support ICIs as a shift from an initial posterior-line palliative scheme to a first-line selection strategy and the continuation of largescale clinical trials.However,no definitive conclusion has been reached regarding the best iTNT application for LARC.Recent studies have shown that short-course radiotherapy and sequential neoadjuvant chemotherapy,combined with immunotherapy,can achieve good shortterm outcomes.Finally,identifying other new biomarkers may facilitate the identification of patients with pMMR/MSS who are sensitive to immune drugs(especially for low rectal cancer).In the future,the treatment strategy of LARC should be combined with the stratification of clinical recurrence risk and patient willingness for organ retention to achieve stratified and accurate treatment.This article will review the related research background,basic and clinical research progress and existing problems of iTNT in LARC.