直肠癌内照射在低位和老年患者中的应用进展

Advances in research on endorectal brachytherapy for aged patients with distal rectal carcinoma

低位直肠癌尤其年老体弱不耐受手术者,保留肛门功能,维持良好的生活质量是患者的诉求,也是临床一直面临的挑战。尽管新辅助放化疗或全程新辅助治疗(TNT)后临床完全缓解率(cCR)达到24%~49%,采用等待观察策略使部分患者免于或延迟肛门切除,但依然面临局部复发风险。研究证实,直肠癌放疗效果与剂量存在剂量-效应关系,局部剂量达到72~92 Gy,才可能达到50%的cCR,但常规外照射(EBRT)剂量仅45~54 Gy,进一步提高局部剂量会导致正常器官或组织的严重损伤。内照射直接针对肿瘤照射,射程短,剂量跌落快,提高局部剂量同时可保护周围器官甚至对侧正常直肠黏膜免受照射。直肠癌内照射有两种主要方式,50 kV接触X射线治疗(CXB)及高剂量率后装照射(HDR-BT)。本综述归纳分析直肠癌内照射最新研究进展,证实内照射有较高的临床缓解率及长期局部控制率,较低的不良反应,更适合高龄体弱不耐受手术及低位直肠癌有保肛诉求的患者。

The preservation of anal sphincter function is an urgent demand for patients with distal rectal carcinoma who expect a good quality of life,especially for aged patients intolerant to surgery due to their poor physical conditions,always posing clinical challenges.Although the clinical complete response(cCR)rates of 24%-49%achieved by neoadjuvant chemoradiotherapy or total neoadjuvant therapy(TNT)allow partial patients to avoid or delay anal resection by adopting a wait-and-see strategy,they still face the risk of local recurrence.Studies have confirmed a dose-response relationship in radiotherapy for rectal cancer,with local doses ranging from 72 to 92 Gy potentially achieving a cCR rate of 50%.In contrast,the tolerated doses for conventional external beam radiotherapy(EBRT)vary between 45 and 54 Gy,while higher doses may cause severe damage to normal organs or tissues.Endorectal brachytherapy,characterized by direct irradiation of tumors,a short irradiation range,and rapid dose fall-off,increases local exposure dose while protecting surrounding organs and even the contralateral normal rectal mucosa.Two main modalities of endorectal brachytherapy are available:50 kV contact X-ray therapy(CXB)and high-dose-rate brachytherapy(HDR-BT).This review summarizes and analyzes the latest advances in research on endorectal brachytherapy,demonstrating its association with higher cCR rates,long-term local control rates,and lower adverse reaction rates.Therefore,endorectal brachytherapy is a more beneficial alternative for aged patients with distal rectal carcinoma who are intolerant to surgery due to their poor physical conditions and require anal sphincter preservation.