[Pathological insights of radiotherapy-related damage to surgical margin after preoperative radiotherapy in patients with rectal cancer].

Objective: To investigate the effect of irradiation to anastomosis from preoperative radiotherapy for patients with rectal cancer by studying the pathological changes. Methods: In this retrospective study, patients enrolled in the FOWARC study from January 2011 to July 2014 in the Sixth Affiliated Hospital of Sun Yat-Sen University were included. In the FOWARC study, enrolled patients with local advanced rectal cancer were randomly assigned to receive either neoadjuvant chemo-radiotherapy or chemotherapy. Among these patients, 23 patients were selected as radiation proctitis (RP)group, who fulfilled these conditions: (1) received neoadjuvant chemo-radiotherapy followed by sphincter-preserving surgery; (2) developed radiation proctitis as confirmed by preoperative imaging diagnosis; (3) had intact clinical samples of surgical margins. Twenty-three patients who had received neoadjuvant chemo-radiotherapy but without development of radiation proctitis were selected as non-radiation proctitis (nRP) group. Meanwhile, 23 patients received neoadjuvant chemotherapy only were selected as neoadjuvant chemotherapy (CT) group. Both nRP and CT cases were selected by ensuring the basic characteristics such as sex, age, tumor site, lengths of proximal margin and distal margin all maximally matched to the RP group. Both proximal and distal margins were collected for further analysis for all selected cases. Microscopy slices were prepared for hematoxylin & eosin staining and Masson staining to show general pathological changes, and also for immunohistochemistry with anti-CD-34 as primary antibody to reveal the microvessel. Microvessel counting in submucosal layer and proportion of macrovessel with stenosis were used to evaluate the blood supply of the proximal and distal end of anastomosis. A modified semi-quantitative grading approach was used to evaluate the severity of radiation-induced injury. Either ANOVA analysis, Kruskal-Wallis rank-sum test or χ(2) test was used for comparison among three groups, and Mann-Whitney U test was used for comparison between two groups. Results: Compared to group of neoadjuvant chemotherapy only, patients receiving neoadjuvant chemo-radiotherapy had lower microvessel count in both proximal and distal margins (M(Q(R)): proximal, 25.5 (19.6) vs. 50.0 (25.0), Z=3.915, P=0.000; distal, 20.5 (17.5) vs. 49.0 (28.0), Z=3.558, P=0.000), higher proportions of macrovessel with stenosis (proximal, 9.5% (23.8%) vs. 0, Z=3.993, P=0.000; distal, 11.5%(37.3%) vs. 0 (2.0%), Z=2.893, P=0.004), higher histopathologic score (proximal, 4.0 (2.0) vs. 1.0 (2.0), Z=6.123, P=0.000; distal, 5.0 (3.0) vs. 2.0 (1.0), Z=4.849, P=0.000). In patients receiving neoadjuvant chemo-radiotherapy, compared to nRP group, RP group had lower microvessel count in both proximal and distal margins (proximal, 19.0 (23.0) vs. 30.4 (38.0), Z=2.845, P=0.004; distal, 19.0 (13.0) vs. 30.0(29.1), Z=2.022, P=0.043), higher proportions of macrovessel with stenosis (proximal, 23.0% (40.0%) vs. 0(11.0%), Z=3.248, P=0.001; distal, 27.0% (45.0%) vs. 3.0% (19.0%), Z=2.164, P=0.030). Rate of anastomotic leakage for CT, nRP and RP group were 8.7% (2/23), 30.4% (7/23), and 52.2% (12/23), and the differences among three groups were statistically significant (χ(2)=10.268, P=0.007). Conclusion: Radiation-induced injury existed on both margins of the resected rectal site after preoperative radiotherapy, and those diagnosed as radiation proctitis had more severe microvascular injury.目的： 从病理学角度探讨新辅助放疗对直肠癌切除术后吻合口的影响。 方法： 本研究为回顾性研究，研究对象来自2011年1月至2014年7月入组中山大学附属第六医院FOWARC研究的病例，均为局部进展期直肠癌患者，随机接受新辅助放化疗或新辅助化疗。接受新辅助放化疗联合保肛手术、术前影像学诊断为放射性直肠炎、手术切缘标本完整的23例患者作为直肠炎组；以性别、年龄、肿瘤位置和标本切缘长度进行匹配，在同期接受新辅助放化疗但无放射性直肠炎者及接受新辅助化疗者中各选择23例患者，作为无直肠炎组和化疗组。计算黏膜下层微血管数和狭窄血管比例，评估吻合口近、远端组织血供；采用病理学半定量评分系统综合评估吻合口近、远端组织放射性损伤程度。三组间比较采用方差分析、Kruskal-Wallis秩和检验或χ(2)检验，两两比较采用Mann-Whitney U检验。 结果： 与化疗组相比，接受新辅助放化疗患者手术近、远切缘的微血管计数[M(Q(R))]减少[近切缘：25.5(19.6)比50.0(25.0)，Z＝3.915，P＝0.000；远切缘：20.5(17.5)比49.0(28.0)，Z＝3.558，P＝0.000]，狭窄血管比例增高[近切缘：9.5%(23.8%)比0，Z＝3.993，P＝0.000；远切缘：11.5%(37.3%)比0(2.0%)，Z＝2.893，P＝0.004]，病理评分升高[近切缘：4.0(2.0)比1.0(2.0)，Z＝6.123，P＝0.000；远切缘：5.0(3.0)比2.0(1.0)，Z＝4.849，P＝0.000]。在接受新辅助放化疗患者中，直肠炎组手术近、远切缘的微血管计数较无直肠炎组减少[近切缘：19.0(23.0)比30.4(38.0)，Z＝2.845，P＝0.004；远切缘：19.0(13.0)比30.0(29.1)，Z＝2.022，P＝0.043]，狭窄血管比例增高[近切缘：23.0%(40.0%)比0(11.0%)，Z＝3.248，P＝0.001；远切缘：27.0%(45.0%)比3.0%(19.0%)，Z＝2.164，P＝0.030]。化疗组、无直肠炎组和直肠炎组吻合口漏发生率分别为8.7%(2/23)、30.4%(7/23)和52.2%(12/23)，差异有统计学意义(χ(2)＝10.268，P＝0.007)。 结论： 直肠癌术前放疗对手术近、远切缘造成明显的放射性损伤；其中影像学诊断为放射性直肠炎者，微血管损伤较无放射性直肠炎者更为明显。.