Case Presentation

L.B. is a 68‐year‐old Hispanic man who presented with hematochezia, narrowed stools, and unintentional weight loss over 4 months. A colonoscopy in May 2019 revealed a 6‐cm, nonobstructing, fungating rectal mass 8 cm from the anal verge. Biopsy confirmed a moderately differentiated, invasive adenocarcinoma. Cross‐sectional computed tomography (CT) and abdominal magnetic resonance imaging (MRI) did not show apparent metastatic disease, except for benign cysts in the liver. Subsequent MRI with rectal protocol showed a clinical T3N1 (cT3cN1, 8th edition American Joint Committee on Cancer [AJCC]) tumor with extramural vascular invasion and nonthreatened mesorectal fascia. The carcinoembryonic antigen (CEA) level was 38 ng/mL at the time of diagnosis.

L.B. started neoadjuvant modified folinic acid, fluorouracil, and oxaliplatin (mFOLFOX6) in July 2019 and completed 8 cycles without dose reduction or delay. His rectal bleeding improved significantly, and stool caliber normalized after 2 cycles of neoadjuvant induction chemotherapy (INCT). Two weeks after completion of INCT in November 2019, restaging rectal MRI demonstrated a radiographic near complete response (CR) with resolution of pathologic lymph nodes and extramural vascular invasion. The CEA level decreased to 7.6 ng/mL yet remained elevated. Endoscopic evaluation showed an erythematous scar with slight mucosal irregularity and nodularity, consistent with partial treatment effect (Fig. 1).

L.B. then proceeded with long‐course chemoradiation (CRT) with capecitabine, which he completed in December 2019. Restaging CT did not demonstrate distant metastatic disease. His CEA level normalized to 4.7 ng/mL, but rectal MRI interpreted residual viable disease T1/T2N0, with persistent, intermediate T2 signal as well as a high signal on diffusion‐weighted imaging (DWI). Endoscopically, he had a scar with telangiectasia and decreased mucosal erythema but persistent, subtle, pale mucosal nodules. Given the excellent treatment response to total neoadjuvant therapy (TNT), a short‐interval reassessment from completion of TNT was planned to evaluate whether an additional interval of time would result in a clinical CR (cCR), so that a watch‐and‐wait (WW) approach might be considered. A repeated rectal MRI 10 weeks after completion of TNT again showed an intermediate T2 signal, radiographically consistent with persistent, viable tumor. However, endoscopic evaluation now showed a flat, white scar with telangiectasia and was consistent with a cCR.

Given the discordance between MRI and endoscopy findings, a radical rectal resection was pursued. The patient and family expressed their understanding that there was a moderately high likelihood that no residual disease would be found in the resected specimen; however, they wished to proceed with the operation. He underwent a robotic low anterior resection with diverting loop ileostomy in April 2020, with final pathology demonstrating no residual adenocarcinoma, a pathologic CR (pCR) (negative pathologic tumor and lymph node status [ypT0ypN0]). His recovery was unremarkable and thus he underwent ileostomy reversal in June 2020. He is currently under surveillance with normal CEA and no radiographic evidence of disease. He experiences urgency and clustering of bowel movements, consistent with low anterior resection syndrome.

中文翻译：

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局部晚期直肠腺癌：治疗顺序、强化和直肠器官保护

案例展示

LB 是一名 68 岁的西班牙裔男性，在 4 个月内出现便血、大便变窄和体重意外下降。2019 年 5 月的结肠镜检查显示，在距肛门边缘 8 厘米处有一个 6 厘米、无阻塞、呈真菌状的直肠肿块。活检证实为中度分化的浸润性腺癌。除肝脏良性囊肿外，横断面计算机断层扫描 (CT) 和腹部磁共振成像 (MRI) 未显示明显的转移性疾病。随后的直肠 MRI 显示临床 T3N1（cT3cN1，第 8 版美国癌症联合委员会 [AJCC]）肿瘤伴有壁外血管侵犯和无威胁的直肠系膜筋膜。诊断时癌胚抗原 (CEA) 水平为 38 ng/mL。

LB 于 2019 年 7 月开始新辅助修饰的亚叶酸、氟尿嘧啶和奥沙利铂（mFOLFOX6），并在没有减少剂量或延迟的情况下完成了 8 个周期。在接受 2 个周期的新辅助诱导化疗 (INCT) 后，他的直肠出血明显改善，大便口径恢复正常。在 2019 年 11 月完成 INCT 后两周，再分期直肠 MRI 显示放射学接近完全缓解（CR），病理淋巴结和壁外血管浸润消退。CEA 水平降至 7.6 ng/mL，但仍保持升高。内镜评估显示红斑瘢痕，粘膜轻微不规则和结节，与部分治疗效果一致（图1）。

LB 随后进行了卡培他滨长程放化疗 (CRT)，他于 2019 年 12 月完成。再分期 CT 未显示远处转移性疾病。他的 CEA 水平正常化为 4.7 ng/mL，但直肠 MRI 解释为残留存活疾病 T1/T2N0，具有持续的中间 T2 信号以及弥散加权成像 (DWI) 上的高信号。内镜下，他有毛细血管扩张的疤痕，粘膜红斑减少，但有持续的、细微的、苍白的粘膜结节。鉴于对完全新辅助治疗 (TNT) 的良好治疗反应，计划从 TNT 完成后进行短间隔重新评估，以评估额外的时间间隔是否会导致临床 CR (cCR)，以便观察和等待(WW) 方法可能会被考虑。TNT 完成 10 周后重复直肠 MRI 再次显示中间 T2 信号，放射学上与持续存在的存活肿瘤一致。然而，内镜评估现在显示平坦的白色疤痕伴毛细血管扩张，与 cCR 一致。

鉴于 MRI 和内窥镜检查结果不一致，进行了根治性直肠切除术。患者及家属表示理解，切除标本中未发现残留病灶的可能性为中高；然而，他们希望继续进行这项行动。他于 2020 年 4 月接受了机器人低位前切除术和回肠环造口术，最终病理显示没有残留腺癌，病理学 CR (pCR)（阴性病理肿瘤和淋巴结状态 [ypT0ypN0]）。他的恢复并不显着，因此他于 2020 年 6 月接受了回肠造口术逆转。他目前正在接受监测，CEA 正常，没有疾病的放射学证据。他的排便急迫和成群结队，符合低位前切除综合征。