Background: Rectal cancer is common and frequently treated with neoadjuvant radiotherapy prior to surgery to reduce the risk of tumour recurrence. However, the therapeutic benefits and side effects of radiotherapy can vary between patients, and there are currently no validated biomarkers to predict treatment response. Tumour cell density (TCD) and tumour-infiltrating lymphocyte (TIL) density are proven prognostic biomarkers in colorectal cancer; however, their utility in predicting radiotherapy response remains unclear. We assessed the prognostic and predictive value of TCD and TIL density in rectal cancer patients treated with radiotherapy.Methods: TCD was quantified using a manual point-counting method in 253 pre-treatment biopsies and across the entire tumour area of 569 resection specimens from the MRC CR07 clinical trial, which randomised patients to either neoadjuvant short-course radiotherapy (SCRT) or straight to surgery (control). TIL density was measured in 102 biopsies and matched resection specimens (73 SCRT, 29 control) across different tumour areas using deep learning-based cell detection in MIM (HeteroGenius Ltd., Leeds, UK). Cutoffs for low/high-TCD and TIL density were both pre-defined and derived from survival data using the survminer R package. Survival analyses were performed to evaluate the predictive and prognostic value of TCD/TIL in relation to overall and cancer-specific survival.Results: TCD in the resection specimens was lower in the SCRT group (19.9%, IQR 12.9–26.7%) than the control group (34.3%, IQR 27.7–40.5%,p< 0.001). In control resections, low-TCD was associated with a higher risk of all-cause mortality (HR 2.20, 95% CI 1.41–3.44,p< 0.001) and cancer-related death (HR 2.69, 95% CI 1.41–5.13,p= 0.0026). In contrast, after SCRT, low resection TCD was associated with a reduced risk of death (HR 0.63, 95% CI 0.40–0.98,p= 0.04). In the SCRT group, low biopsy TCD prior to radiotherapy was associated with a reduced risk of cancer-related death (HR 0.34, 95% CI 0.13–0.89,p= 0.028). Across both trial arms, TIL density was higher in pre-treatment biopsies than resections (2492 vs. 1304/mm2,p< 0.001). Low biopsy TIL density was associated with an increased risk of all-cause mortality (HR 2.43, 95% CI 1.24–4.76,p= 0.01). The SCRT group had lower TIL density in the resection compared with controls (1210 vs. 1615/mm2,p< 0.001), and low resection TIL density across the whole tumour area was associated with a higher risk of death (HR 2.55, 95% CI 1.11–5.87,p= 0.027).Conclusions: Our findings support the role of TCD and TIL density as quantitative biomarkers in rectal cancer patients. TCD can be used to assess the degree of response to radiotherapy, and contrasting survival associations are observed between straight-to-surgery and SCRT-treated patients. This study raises the possibility of using TCD as both a prognostic and predictive biomarker. TIL density failed to show predictive value but demonstrated expected prognostic associations.
背景：直肠癌较为常见，术前常采用新辅助放疗以降低肿瘤复发风险。然而，放疗的治疗获益与副作用存在个体差异，目前尚无经过验证的生物标志物可预测治疗反应。肿瘤细胞密度（TCD）和肿瘤浸润淋巴细胞（TIL）密度已被证实是结直肠癌的预后生物标志物，但其在预测放疗反应方面的作用尚不明确。本研究评估了接受放疗的直肠癌患者中TCD与TIL密度的预后及预测价值。 方法：在MRC CR07临床试验中，采用人工点计数法对253例治疗前活检样本及569例手术切除标本（患者随机分配至新辅助短程放疗组或直接手术对照组）的全肿瘤区域进行TCD定量。通过基于深度学习的细胞检测技术（MIM系统，英国利兹HeteroGenius有限公司），在102例活检样本及匹配的切除标本（73例放疗组，29例对照组）的不同肿瘤区域测量TIL密度。采用survminer R包根据生存数据预先定义并确定TCD与TIL密度的高/低截断值。通过生存分析评估TCD/TIL对总生存期和癌症特异性生存期的预测及预后价值。 结果：放疗组切除标本的TCD（19.9%，IQR 12.9–26.7%）低于对照组（34.3%，IQR 27.7–40.5%，p<0.001）。在对照组切除标本中，低TCD与更高的全因死亡风险（HR 2.20，95% CI 1.41–3.44，p<0.001）和癌症相关死亡风险（HR 2.69，95% CI 1.41–5.13，p=0.0026）相关。相反，在放疗组中，低切除TCD与死亡风险降低相关（HR 0.63，95% CI 0.40–0.98，p=0.04）。放疗组中，放疗前活检低TCD与癌症相关死亡风险降低相关（HR 0.34，95% CI 0.13–0.89，p=0.028）。两组患者的治疗前活检TIL密度均高于切除标本（2492 vs. 1304/mm²，p<0.001）。活检低TIL密度与全因死亡风险增加相关（HR 2.43，95% CI 1.24–4.76，p=0.01）。放疗组切除标本的TIL密度低于对照组（1210 vs. 1615/mm²，p<0.001），且全肿瘤区域低切除TIL密度与更高的死亡风险相关（HR 2.55，95% CI 1.11–5.87，p=0.027）。 结论：本研究结果支持TCD与TIL密度作为直肠癌定量生物标志物的作用。TCD可用于评估放疗反应程度，且在直接手术与接受短程放疗的患者中观察到相反的生存关联。本研究提示TCD兼具预后与预测生物标志物的应用潜力。TIL密度虽未显示预测价值，但表现出预期的预后关联。
肿瘤(癌症)患者之家