A growing number of early-stage RCCs are being diagnosed with advances in imaging technology. Despite the increase in early intervention treatments, RCC-specific mortality has not significantly improved. This has resulted in the need of a more effective approach to improve patient survival. Artificial intelligence (AI) has been increasingly used in the medical field in recent years. It is in its early stages of application in the field of RCC, but its successful application in other medical fields foretells a great potential in the field of RCC. In this study, a model for preoperative prediction of Ki-67 expression in RCC patients was created and validated by deep learning (DL) technology based on combined four-phase CT images of RCC patients. Thanks to the advantages of non-invasiveness, reduction of complications, and ease of acceptance, the model assists subordinate hospitals in understanding the Ki-67 expression of RCC patients. It is expected to be applied to clinical practice in the future to facilitate the development of individualized treatment plans.
Ki-67 is a broadly recognized marker for tumor prognosis [11–13]. In theory, histopathological changes are well characterized by imaging techniques. Radiomic features can quantify the image pixel and gray scale distribution to mirror molecular pathological changes. In this sense, Ki-67 expression prediction based on CT images is feasible [14]. Studies have been conducted to predict Ki-67 expression using AI technology, primarily centered on other tumors. But in any case this shows the promise of AI technology in the field of RCC [15–17]. In this study, Ki-67 expression was predicted by deep learning (DL) technology based on combined four-phase CT images of RCC patients. The results yielded a prediction accuracy of more than 70% for all five models, and the optimal model, the venous phase model of Mobilenetv3-large, showed good prediction efficacy with average accuracy, sensitivity, precision, F1-score and AUC value of 0.784, 0.764, 0.789, 0.770 and 0.823, respectively. No additional studies were found to similarly utilize AI technology to predict Ki-67 expression in RCC, highlighting a key innovative point of the present study.
Mobilenetv3 is a type of DL convolutional neural network that has achieved satisfactory achievements in the medical field. Take the study of Huang et al. [18] as an example, they constructed a recognition model for digitized pathology slide images of breast cancer by using Mobilenetv3 network combined with bilinear structure, with a classification accuracy as high as 0.88. Mobilenetv3-large, as a branch of the Mobilenetv3 network, prioritizes improving prediction accuracy. We made an initial attempt to model Ki-67 expression prediction in RCC patients using the Mobilenetv3-large network, yielding prediction accuracies above 70% in all cases and up to 78.4% in the venous phase.
There is a wealth of relevant research on AI in the field of RCC, such as the differentiation of benign and malignant renal masses. Baghdadi et al. [19] collected CT images of 212 patients with pathologically diagnosed renal oncocytoma and chRCC and developed a model to discriminate benign renal oncocytoma from chRCC using convolutional neural network with 95% accuracy, 100% sensitivity and 89% specificity. Apart from that, AI also functions in the prediction of pathologic grading of RCC. Xu et al. [20] developed a Fuhrman grading prediction model for ccRCC using DL algorithm. They collected CT images of 706 patients with ccRCC, with 592 patients as the training group and 114 patients as the validation group, and defined patients with grade Ⅰ and Ⅱ as the low-grade group and patients with grade Ⅲ and Ⅳ as the high-grade group. The results yielded an accuracy of 82% for the model with an AUC of 0.882. AI has also been applied in the identification of pathologic types of RCC. Han et al. [21] undertook the first study of classifying RCC subtypes based on DL algorithm, where triphasic CT images of 169 RCC patients were collected and used to train the established DL model. The results yielded an accuracy of 85% for the DL algorithm with an AUC of 0.9. There are even applications of AI in the prediction of pathological staging, gene mutation, and prognosis of renal carcinoma [22–24]. The majority of current studies, however, maintain a focus on the prediction of ccRCC, considering that there are fewer predictions related to pathological immunohistochemistry and that the main pathologic type of RCC is ccRCC. Though most of the patients enrolled in this study were suffering from ccRCC whereas few patients with pRCC and chRCC were enrolled, we have covered the pathologic types of ccRCC, pRCC, and chRCC, resulting in a more comprehensive variety of predictions, which may be more suitable for clinical application. In the future, more enrolled patients as well as pRCC and chRCC patients are needed to further improve the predictive efficacy of the AI models so that they are more clinically applicable.
Data volume is influential on the performance of DL technology applied to image analysis, i.e., an increase in data volume improves the model prediction performance [25]. Data enhancement techniques allow augmentation of data without changing the data labels and increase image heterogeneity. In this study, the prediction performance was improved by the data augmentation technique because of a lower data volume in the high-grade group. However, the high-grade group was still lower than the low-grade group in terms of F1-score and sensitivity after data augmentation. This suggests that while data augmentation techniques may compensate for data deficiencies, there is still a need to collect more high-grade patient data to make the data volume more balanced and improve predictive performance.
There are still certain limitations to this study: small patient volume, insufficient data volume, single-center study, RCC type dominated by ccRCC, and potential absence of scientific validity of Ki-67 threshold setting. In this regard, multicenter studies should be conducted in the future in which data from different hospitals and devices are added to improve the generalizability of the model. In addition, MRI images may be employed in the future to improve predictive efficacy.