In this study, we presented and validated a fusion DLRN model based on longitudinal ultrasound images to personalize prediction the risk of breast tumor residual and LNM invasion after performing NAC for BC patients. The DLRN achieved favorable results in terms of AUC, sensitivity, specificity, and decision curves. Also, the results of survival analysis demonstrated the applicability of the fusion model in clinical practice. Our study confirmed that the fusion model could assist clinicians adjusting treatment regimens for patients, thereby increasing the disease-free survival and overall survival of patient.
The dynamic detection of tumor size, echo, and morphology is routinely used to assess the NAC response, but they are considered relatively late predictors in the NAC process[18, 19]. With the development of ultrasound imaging technology, some studies have reported that traditional ultrasound combined with shear wave elastography or dynamic contrast enhanced ultrasound (CEUS) has improved the predictive ability of NAC treatment response through quantitative parameters. But the diagnostic performance is moderate[20, 21]. Radiomics and deep learning are emerging interdisciplinary combining medical imaging and the computer field, which extracts lots of quantitative information from medical images and shows great potential to assist in clinical diagnosis and treatment[11, 22, 23]. Radiomics and deep learning have been widely used in non-invasive prediction of neoadjuvant chemoradiotherapy responses in various malignant tumors,especially in breast cancer[24]. Previous studies have evaluated the treatment response using radiomic or deep learning methods based on ultrasound images. Recently, Zhang et al.[25] constructed a nomogram for predicting the response of patients with axillary lymph node (ALN) positive breast cancer to neoadjuvant chemotherapy (NAC), with AUC value of 0.855. Further, Gu et al.[16] have proposed two novel DLR models(DLR‐PCR and DLR‐LNM) to assessed the the status of tumors and lymph node metastasis (LNM) independently after NAC, with AUC value of 0.948, 0.896, respectively. From these studies, both traditional radiomics and deep learning models yielded some acceptable results and showed certain advantages in predicting the treatment response after NAC. However, there are few fusion models that package deep learning features with radiomics features and clinical characteristics for the prediction of the status of tumors and LNM in BC patients.
Previous studies have reported that the clinical assessment method based on the images and clinical characteristics has limited performance and clinical practicality[26]. The reason may be due to the subjectivity and empiricism of humans in determining the effectiveness of NAC, as well as their inability to consistently and accurately identify changes in the tumor micro-environment caused by NAC. The clinical features selected in our study are consistent with previous studies, and the performance of clinical models on each task is limited[27]. Nevertheless, when we integrating clinical, radiomics, and deep transfer learning features together, the DLRN have achieved much better and satisfactory AUCs for predicting tumor and LNM status, confirming the effectiveness of the fusion model for predicting the status of tumor and LNM in BC patients. This result also reflects that deep learning model may be able to extract high-level abstract features related to tumor micro-environment changes caused by NAC treatment.
The purpose of survival analysis is to analyze the factors that lead to events such as patient death or recurrence within a certain period of time after treatment, and it has important clinical application value[28].When clinicians have a more accurate assessment of the patient's survival risk, they are more likely to choose appropriate treatment methods[29]. In this study, we developed a survival model that effectively integrates clinical, radiomics and deep learning data to more accurately predict the survival rate of BC patients, in order to verify the effectiveness of the fusion algorithm and promote clinical application. The results of this study showed that the fusion model can better distinguish high and low risk groups, and has a better ability to predict the survival of breast cancer, which proves the availability of the fusion model in predicting the prognosis of breast cancer.
Our research also has some limitations. Firstly, our study has a small sample size and is a single center study, requiring a larger sample size and multi-center studies to validate our results. Secondly, this is a retrospective analysis. Thirdly, we only used the US data to develop models, and more medical images, including pathological whole slide images and MRI images, might improve our models.