Regarding the clinical risk factors, the study found that sex, age, tumor location, tumor size, pathology, destruction, ALP, LDH, and metastasis at diagnosis did not significantly differ between the patients with local relapse (LRs) and those without local relapse (NLRs). These findings are consistent with previous research.[7] However, other studies have identified age (pediatric patients having an increased risk of relapse), tumor size (tumors larger than 8cm having a significantly higher risk of relapse), higher pre-treatment levels of LDH being associated with an increased risk of relapse, and the presence of metastasis at diagnosis being a strong indicator of a higher risk of relapse. [8–11] The discrepancies in the results may be attributed to factors such as inadequate sample size, geographical constraints, and the complex biological processes involved in osteosarcoma relapse, including the aberration of multiple genes and the influence of various risk factors. Radiomics, an emerging field in medical imaging, holds great potential in enhancing the diagnosis and treatment of various diseases, including osteosarcoma[12–15]. Its application in investigating the relapse of osteosarcoma can shed light on the intricate biological processes involved, helping to unravel the aberration of multiple genes and the influence of various risk factors. By utilizing radiomics, researchers can expand the sample size, overcome geographical constraints, and delve into the complexities of osteosarcoma relapse, providing valuable insights and paving the way for improved management strategies.
In this study, we used four machine-learning-based radiomics models based on radiograph and MRI to predict local relapse (LR) in extremity high-grade osteosarcoma. X-Ray imaging is routinely used for diagnosis and evaluation of osteosarcoma. In the past, most of the radiomics studies on bone tumors focused on CT and MRI, but in recent years, machine-learning-based radiomic analysis has emerged as a powerful tool for extracting quantitative features from X-Ray images and using these features for predicting clinical outcomes in bone tumors. Several studies have demonstrated the potential of radiograph radiomic analysis in predicting for the differentiation of benign and malignant bone tumors[16], efficacy of newadjuvant chemotherapy[17] and lung metastasis[18] in osteosarcoma patients. These studies have shown that radiomic features extracted from radiograph images can be used as predictors of local relapse. This study describes the use of preoperative radiograph radiomics to distinguish between LRs and NLRs. The AUC of the model for each classifier (XGB, LR, SVM and RF) in the test set were 0.611, 0.541, 0.723 and 0.627, respectively. The AUC obtained from radiomics based on radiograph were not very high. The explanation behind this is that radiograph imaging may have inherent limitations, such as low spatial resolution or limited ability to capture subtle variations in tissue characteristics. These limitations can affect the ability of radiomics models to accurately predict outcomes, resulting in a lower AUC. Furthermore, we discovered that among the features extracted from the radiograph images, only one firstorder feature (logarithm_firstorder_Median) was selected. This feature described the distribution of pixel or voxel intensities, providing additional quantitative information within the ROI. However, when compared to other studies, the feature selection from the radiograph we made may not fully capture the intratumoral heterogeneity of osteosarcoma.
In our study, the AUC using MRI-based radiomics of the model for each classifier (XGB, LR, SVM and RF) in the testing set were 0.609, 0.759, 0.727 and 0.705, respectively. The AUC obtained through the utilization of MRI-based radiomics, specifically employing the LR, SVM, and RF models, exhibited a slight superiority over the utilization of radiograph in the prediction of local relapse (LR) in osteosarcoma. Our analysis involved the examination of image data from a cohort of 92 osteosarcoma patients, and through the application of machine learning techniques, we were able to establish a strong correlation between pre-therapy MR radiomics features and tumor heterogeneity. Subsequently, we identified eleven statistically significant high-level features from the MRI images that displayed a substantial association with local relapse. It is worth noting that a previous study has already demonstrated that the radiomic features significantly linked to relapse in osteosarcoma are derived from CE-T1WI[19]. Therefore, our study, along with previous research findings, provides evidence to endorse the inclusion of CE-T1WI in radiomic investigations pertaining to osteosarcoma. Among the radiomic attributes derived from MRI, nine of them are associated with texture features acquired through wavelet transformation. The wavelet transformation technique assesses signal resolution across different temporal, spatial, and frequency scales, thereby providing insights into the organization of tissue microstructure. The extraction of wavelet features from DCE-MRI has demonstrated its efficacy in capturing the heterogeneity observed in breast cancer[20] and osteosarcoma[21].
While both X-Ray and MRI radiomic analyses have demonstrated potential in predicting local relapse in osteosarcoma, the integration of these two modalities has the potential to further enhance prediction accuracy. By amalgamating the complementary information derived from radiograph and MRI images, machine-learning algorithms can acquire more robust predictive models. Recent studies have documented the successful integration of radiograph and MRI radiomic features for preoperative prognostication of osteosarcoma outcomes, encompassing local relapse. The diagnostic performance of the combined features of radiograph and MRI in this investigation achieved a slightly higher AUCs compared to that of the individual sequence. The AUC using radiograph and MRI-based radiomics of the model for each classifier (XGB, LR, SVM and RF) in the testing set were 0.681, 0.759, 0.768 and 0.868, respectively. Previous and current research indicates that combining multiple models proves to be more beneficial, particularly in cases where the performance of a single model is lacking.[22, 23]
RF is effective at capturing non-linear relationships between radiomics features and the target variable. [24] It performs well in complex and non-linear scenarios and can handle high-dimensional data with a limited number of samples. RF also provides a measure of feature importance, allowing for the identification of significant radiomics features that contribute to the prediction and enhancing model interpretability. [25] These advantages make RF particularly suitable for small-sample radiomics studies with limited samples and complex relationships between features and outcomes. The RF had best predictive efficiency (AUCs: training set 0.999 vs. test set 0.868) of four machine learning models in our study. It was well consistent with the obtained results and previous literature.[26–28]
The study provides valuable insights into the potential of machine learning algorithms to predict local relapse in osteosarcoma patients. However, there are certain limitations in the study that need to be acknowledged. Firstly, the study is based on retrospective data analysis, which introduces inherent biases and limitations. The data used in the study might not represent the true population and could be subject to selection bias. The accuracy of the predictions generated by the machine learning model can only be as good as the quality and representativeness of the data used for training it. Secondly, the sample size in this study is relatively small. With only a limited number of patients included, the generalizability and reliability of the results may be compromised. A larger sample size would have provided a more robust and statistically meaningful analysis. Additionally, manual delineation of ROI can be time-consuming and challenging, especially with extensive datasets or intricate anatomical structures. This can slow down the research process and hinder efficiency. Moreover, manual delineation relies on the subjective judgment of the observer, leading to potential bias and limiting the reproducibility and generalizability of the findings. It is crucial to assess the accuracy and repeatability of VOI in future studies. For larger sample sizes, automated or semi-automated segmentation methods could be utilized to save time and streamline the process. Furthermore, the impact of external factors, such as patient demographics, lifestyle, and comorbidities, is not considered in this study. These factors could significantly influence the risk of local relapse in osteosarcoma patients. Incorporating such variables into the machine learning model could enhance its predictive accuracy and clinical utility. Overall, the study provides a promising foundation for the use of machine learning in predicting local relapse in osteosarcoma. However, these limitations should be considered when interpreting the findings, and further research with larger sample sizes and comprehensive predictive models is warranted.