Discussion
tumor, extra-pancreatic neuropathy, Pancreatic cancer, fibrosis, PDAC, fibrous stroma, MR
TUMOR, RECURRENCE, METASTASIS, LIVER METASTASIS, PANCREATIC CANCER, FIBROSIS, LYMPH NODE METASTASIS, LIVER METASTASIS
Because clinical model provided a deplorable prediction value for liver metastasis after surgery, we had to consider the value of pathological staining for these patients receiving operation. To evaluate the predictive value of fibrosis in liver metastasis, we randomly chose 54 patients from the internal cohort with post-operation pancreas specimens (25 liver metastasis vs. 29 non-Liver metastasis) and took IHC test for CAFs markers. We selected α-SMA as a representative marker for fibrosis and the detailed standards of IHC scores were shown in Additional file IHC score of α-SMA in PDAC promoting radiomics model. Liver metastasis is a common and serious outcome for PDAC patients, and patients relapsed with liver metastasis had a worse prognosis compared those without recurrence [In radiomics features, histogram feature is a low-order radiomics parameter, describing the distribution of voxel intensities related to the properties of individual pixels [In our analysis, age was a protection factor for liver metastasis and older patients were much easier to occur to liver metastasis. Patients with lymph node metastasis seemed much easier to occur to liver metastasis after surgery, which were not confirmed in our validation cohort. Though PDAC with high tumor size (T stage) or lymph node metastasis had higher likelihood of metastasis, patients including in our analysis had no advanced metastasis before surgery and most of them received complete R0 resection, which is the possible reason why tumor size and lymph node metastasis had worse prediction value in our cohort. Previous study also reported tumor region and extra-pancreatic neuropathy might had association with liver metastasis post-operation [Due to the poor predictive value of clinical characteristics for liver metastasis in PDAC patients receiving surgery, we tried to use pathological staining to enhance our radiomics model. Compared with clinical characteristics, pathological signatures seemed to have a better ability to reflect bio-behaviors of PDAC. Pancreatic cancer is rich in fibrous stroma and CAFs are the main cells mostly from mesenchymal origin found in tumor microenvironment playing an important role in fibrosis [However, there are still several limitations in our study. First, it was a retrospective study with heterogeneity in MR acquisition among different MR scanners between three different hospital centers. Therefore, we made normalization and resample before radiomics features extraction to reduce heterogeneity, and further work might concentrate on a prospective verification of our risk model based on standard MR scanning protocol and unified MR scanner. Second, the cases with specimen for IHC analysis were limited and much CAFs associated marker were also considered to including in further risk model. Third, due to the limitation of amounts of patients in three hospital centers, we mixed patients and divided into development and validation cohorts, and further study should include more patients from different centers to validate our model.
In conclusion, this research established and validated a radiomics model to predict liver metastasis after surgery in PDAC patients. This prediction model can assist clinicians to decide clinical treatment after operation for patients with high risk of liver metastasis. CAFs markers has their own potential to predict liver metastasis combining with radiomics, but still need a further validation.