Table_1_Which Definition of Upper Rectal Cancer Is Optimal in Selecting Stage II or III Rectal Cancer Patients to Avoid Postoperative Adjuvant Radiation?.docx

BackgroundIn most guidelines, upper rectal cancers (URC) are not recommended to take neoadjuvant or adjuvant radiation. However, the definitions of URC vary greatly. Five definitions had been commonly used to define URC: 1) >10 cm from the anal verge by MRI; 2) >12 cm from the anal verge by MRI; 3) >10 cm from the anal verge by colonoscopy; 4) >12 cm from the anal verge by colonoscopy; 5) above the anterior peritoneal reflection (APR). We hypothesized that the fifth definition is optimal to identify patients with rectal cancer to avoid adjuvant radiation.
MethodsThe data of stage II/III rectal cancer patients who underwent radical surgery without preoperative chemoradiotherapy were retrospectively reviewed. The height of the APR was measured, and compared with the tumor height measured by digital rectal examination (DRE), MRI and colonoscopy. The five definitions were compared in terms of prediction of local recurrence, survival, and percentages of patients requiring radiation.
ResultsA total of 576 patients were included, with the intraoperative location of 222 and 354 tumors being above and straddle/below the APR, respectively. The median distance of the APR from anal verge (height of APR) as measured by MRI was 8.7 (range: 4.5–14.3) cm. The height of APR positively correlated with body height (r=0.862, P<0.001). The accuracy of the MRI in determining the tumor location with respect to the APR was 92.1%. Rectal cancer above the APR had a significantly lower incidence of local recurrence than those straddle/below the APR (P=0.042). For those above the APR, there was no significant difference in local recurrence between the radiation and no-radiation group. Multivariate analyses showed that tumor location regarding APR was an independent risk factor for LRFS. Tumor height as measured by DRE, MRI and colonoscopy were not related with survival outcomes. Fewer rectal cancer patients required adjuvant radiation using the definition by the APR, compared with other four definitions based on a numerical tumor height measured by MRI and colonoscopy.
ConclusionsThe definition of URC as rectal tumor above the APR, might be the optimal definition to select patients with stage II/III rectal cancer to avoid postoperative adjuvant radiation.

研究背景：在多数临床指南中，上段直肠癌（upper rectal cancers, URC）并不推荐接受新辅助或辅助放疗。但目前上段直肠癌的定义差异极大，临床常用的定义共有5种：1）经MRI测量距肛缘>10cm；2）经MRI测量距肛缘>12cm；3）经结肠镜测量距肛缘>10cm；4）经结肠镜测量距肛缘>12cm；5）位于前腹膜反折（anterior peritoneal reflection, APR）前方。本研究假设，第五种定义是筛选可豁免辅助放疗的直肠癌患者的最优标准。
研究方法：本研究回顾性分析了接受根治性手术且未行术前放化疗的Ⅱ/Ⅲ期直肠癌患者的临床资料。测量前腹膜反折的位置高度，并与经直肠指诊（digital rectal examination, DRE）、MRI及结肠镜测得的肿瘤位置高度进行对比。基于局部复发预测、生存结局及需放疗患者占比，对五种定义进行比较。
研究结果：本研究共纳入576例患者，其中222例肿瘤位于前腹膜反折前方，354例肿瘤跨越或位于前腹膜反折下方。经MRI测量的前腹膜反折距肛缘中位距离（即前腹膜反折高度）为8.7cm（范围：4.5~14.3cm）。前腹膜反折高度与患者身高呈正相关（r=0.862，P<0.001）。MRI判定肿瘤相对于前腹膜反折位置的准确率为92.1%。位于前腹膜反折前方的直肠癌患者局部复发率显著低于跨越或位于其下方的患者（P=0.042）。对于前腹膜反折前方的直肠癌患者，放疗组与未放疗组的局部复发率无显著差异。多因素分析显示，肿瘤相对于前腹膜反折的位置是无局部复发生存（local recurrence-free survival, LRFS）的独立危险因素。经直肠指诊、MRI及结肠镜测得的肿瘤高度与患者生存结局无相关性。与基于MRI及结肠镜测得的肿瘤数值高度的其余四种定义相比，采用前腹膜反折定义的需辅助放疗的直肠癌患者人数更少。
研究结论：将上段直肠癌定义为前腹膜反折前方的直肠肿瘤，或许是筛选Ⅱ/Ⅲ期直肠癌患者以豁免术后辅助放疗的最优标准。