Purpose

Radiation therapy for locally advanced non-small cell lung cancer (NSCLC) should treat the whole tumor, including its microscopic extensions, and protect adjacent organs at risk as much as possible. The aim of our study is to evaluate the size of microscopic tumor extension (MEmax) in NSCLC, and search for potential predictive factors.

Methods and Materials

We retrospectively selected 70 patients treated with postoperative radiation therapy for a NSCLC with N2 nodal status, then 34 additional patients operated for a squamous cell lung cancer with N1 or N2 nodal status. On the digitized slides originating from the resected tumors of these 104 patients, we outlined the border of the tumor, as seen with the naked eye. We then searched for microscopic tumor extension outside of these borders with a magnification as high as 40 × and measured the maximum size of MEmax.

Results

The median MEmax in the whole cohort was 0.85 mm (0-9.95). The MEmax was <5.3 mm in 95% of adenocarcinomas (6.5 mm in the subgroup without neoadjuvant chemotherapy) and <3.5 mm in 95% of squamous cell carcinomas (3.7 mm in the subgroup without neoadjuvant chemotherapy). After multivariate analysis, the factors associated with the size of MEmax were vascular invasion (P = .0002), histologic type, with a wider MEmax for adenocarcinomas in comparison with squamous cell carcinomas (P = .002), tumor size, which was inversely related with the size of MEmax (P = .024), and high blood pressure (P = .03). Macroscopic histologic tumor size was well correlated with both radiologic tumor size on a mediastinal setting computed tomography (correlation coefficient of 0.845) and on a parenchymal setting computed tomography (correlation coefficient of 0.836).

Conclusions

The clinical target volume margin, accounting for microscopic tumoral extension, could be reduced to 7 mm for adenocarcinomas and 4 mm for squamous cell carcinomas.

中文翻译：

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局部晚期非小细胞肺癌显微肿瘤扩展的大小和预测因素

目的

局部晚期非小细胞肺癌 (NSCLC) 的放射治疗应治疗整个肿瘤，包括其微观扩展，并尽可能保护邻近的处于危险中的器官。我们研究的目的是评估 NSCLC 中微观肿瘤扩展的大小 (MEmax)，并寻找潜在的预测因素。

方法和材料

我们回顾性地选择了 70 名接受术后放射治疗的 N2 淋巴结状态的 NSCLC 患者，然后另外 34 名患者接受了 N1 或 N2 淋巴结状态的鳞状细胞肺癌手术。在源自这 104 名患者的切除肿瘤的数字化载玻片上，我们勾勒出肉眼所见的肿瘤边界。然后我们以高达 40 倍的放大倍数搜索这些边界外的微观肿瘤扩展，并测量 MEmax 的最大尺寸。

结果

整个队列的中位 MEmax 为 0.85 mm (0-9.95)。MEmax 在 95% 的腺癌中 <5.3 mm（在未接受新辅助化疗的亚组中为 6.5 mm），在 95% 的鳞状细胞癌中为 <3.5 mm（在未接受新辅助化疗的亚组中为 3.7 mm）。多变量分析后，与 MEmax 大小相关的因素是血管侵犯 ( P  = .0002)、组织学类型、与鳞状细胞癌相比，腺癌的 MEmax 更宽 ( P  = .002)、肿瘤大小，与与 MEmax 的大小有关 ( P  = .024) 和高血压 ( P = .03）。宏观组织学肿瘤大小与纵隔计算机断层扫描（相关系数为 0.845）和实质计算机断层扫描（相关系数为 0.836）的放射学肿瘤大小密切相关。

结论

考虑到微观肿瘤扩展的临床目标体积边缘，对于腺癌可以减少到 7 毫米，对于鳞状细胞癌可以减少到 4 毫米。