In this study, we provide a new means of preoperative assessment based on radiomics for preoperative prediction of resection margin status prior to pancreaticoduodenectomy for pancreatic head adenocarcinoma. We demonstrate that the radiomics labels displaying significant predictive power for the recognition of the resection margin of the pancreatic ahead adenocarcinoma (> 1 mm vs ≤ 1 mm) were Gray level co-occurrence matrix, Run-length matrix and Wavelet transform. These findings are of significant potential importance for the treatment of pancreatic head adenocarcinoma in the context of previous studies that have identified no difference in survival rate between patients with resection margin of ≤ 1 mm and patients with an R1 resection and the patients might benefit from neoadjucant therapy, especially for the patients with lymph node positive.8 Based on the radiomic parameters established in our study, we can accurately identify the resection margin in the majority of patients before surgery, identifying a potential subgroup of patients that may benefit from neoadjuvant chemotherapy first, rather than directly receiving surgery.
This study confirmed that the resection margin status of resected pancreatic head adenocarcinoma was correlated with worse overall survival (P < 0.05). The overall three-year survival rate was 40.7% for all patients, 51.9% for > 1 mm resection margin patients, and 23.5% for ≤ 1 mm resection margin patients. The overall three-year survival rate in our study was not good as other report. 8 We thought that might cause by inadequate adjuvant chemotherapy. Most patients involved in this study came from west China. Some patients refused adjuvant chemotherapy because they were afraid of adverse reactions of adjuvant chemotherapy. Some patients did not believe that they could get benefits from adjuvant chemotherapy. Thus, only 40% patients were treated with adjuvant chemotherapy. Even though most patients did not treat with adjuvant chemotherapy, resection margin status was also an independent prognostic factor for patients with pancreatic head adenocarcinoma. In the past, the clinical judgment criteria for resection margin status of pancreatic head adenocarcinoma specimens has been inconsistent. In most cases, the absence or presence of tumor cells on the resection margin surface has been used as the basis for R0 or R1 resection.10 As a result, the difference in local recurrence rate and prognosis between R0 and R1 resection patients has occasionally been reported as not statistically significant.28 Verbeke et al. proposed a new international standard based on the "1 mm principle" for R0 resection of resected specimens with circumferential resection margin greater than or equal to 1 mm.29–31 The "1 mm principle" means that no tumor cells within a resection margin greater than 1 mm shall be classified as R0, with the remainder classified as R1.27, 29, 31 Strobel et al. also evaluated the data of 561 patients with pancreatic head adenocarcinoma who underwent pancreaticoduodenectomy by using the "1 mm principle", the results showed that 80% of the patients underwent R1 resection, while only 20% underwent R0 resection, and the difference in prognosis between the two groups was statistically significant.10, 32 Although the "1 mm principle" pointed out the limitations of previous surgical treatment of pancreatic cancer, it remains very difficult to evaluate this significant prognostic factor before surgery, with no current imaging studies currently reported in the literature focused on the resection margin of pancreatic head adenocarcinoma.
Due to the biological characteristics of the tumor itself, there are differences between different texture features in enhanced CT images. However, many of the differences visible on CT images may reflect the radiologists’ subjective impression of image quality, which can mask any underlying biologic heterogeneity.33 Using CT texture analysis, these image features can be detected and objectively quantified.34
The normal pancreatic tissue lacks an obvious capsule and has abundant adipose tissue.35 However, in pancreatic cancer, there is more stroma in the tissue, which is prone to causing fibrosis of surrounding tissues and associated poor blood supply.36 These key tumor biological characteristics can be detected by enhanced CT.37 In this study, we collected the texture characteristics data from 258 portal venous phase images of 86 patients with pancreatic head adenocarcinoma. The ROIs we selected for the resection margin included normal pancreatic tissue and tumor tissue for radiomics methods analysis. We analyzed the images of the resection margin at three layers in patients with pancreatic head adenocarcinoma, rather than the entire tumor at a single layer as in other studies,38, 39 as different resection margins could reflect different tumor biological characteristics present within the heterogenous primary tumor. This makes our study more detailed and representative compared to other studies.40, 41 Our results showed correlations of Gray level co-occurrence matrix, high Gray-level run emphasis of Run-length matrix and average filter of Wavelet transform with resection margin status (> 1 mm vs ≤ 1 mm). Gray level co-occurrence matrix is a texture analysis form that provides statistical measurement of spatial relationship of pixels in images,11 whilst the run length matrix is the length of the continuum element with the same gray level in the preset direction.42 The grayscale run length is only a measurement of image pixel information. In actual practice, it is also necessary to calculate the generated grayscale run length matrix and obtain further image feature information based on the grayscale co-occurrence matrix. The relationship between run lengths produces textures and Wavelet transform is a means of transforming space (time) and frequency, to provide a more effective signal analysis,22 advantageous as it allows the image to be analyzed at multiple scales.22 In this study, the AUC of four characteristic features was 0.784, sensitivity was 75% and specificity was 79%, allowing accurate prediction of ≤ 1 mm resection margins. However, this study also has some limitations. All the extracted features in this study are two-dimensional features of CT images, and should ideally be the features of the entire three-dimensional CT image of the resection margin, so as to provide a more comprehensive assessment of the tumor and potential resection margin status.