An ability to type the primary lung cancer from the MRI images of the BMs would be of great advantage to clinicians especially when conventional invasive procedures like biopsy are difficult to perform[15]. Our results showed that the MR imaging-based radiomic analysis of BMs can serve as a noninvasive technique to differentiate the primary SCLC from NSCLC, and AD from NAD in lung cancer patients. Radiomics holds immense potential for the correlation of imaging features with histopathological changes. These are difficult to achieve by visual inspection alone[16]. Our study provides evidence of the role of radiomics in complementing traditional methods for the pathological classification of BMs.
Our study was novel in that we analyzed MR images of BMs using a radiomics method to classify different lung cancer subtypes. Previous classification of lung cancer by radiomics approach has mainly focused on primary tumors. In a previous study, Tang et al[17] presented the potential of multimodal chest MRI-based radiomics for discrimination between lung squamous cell carcinoma and AD subtypes of NSCLC. Their model obtained an AUC of 0.824 for the test set, which was comparable to computed tomography (CT) or positron emission tomography (PET) based radiomic models for the identification of NSCLC subtypes[18, 19]. Wang et al[20] demonstrated that the multi-parametric MR model has a better predictive efficiency compared with CT and PET-bases radiomic models.
In our study, the multi-sequence radiomics model performed better as compared with the single-sequence models. Studies showed that DWI was of great value in the evaluation of BMs and have demonstrated that most BMs of lung cancer show hyperintensity on DWI[21]. Furthermore, the current guidelines[22] also recommend T1CE as an effective tool and an important indicator in the diagnosis of BMs ,repesenting destruction of the blood-brain barrier; moreover, T2-weighted FLAIR can best detect peritumoral edema in the brain,which aids in distinguishing edema in the brain and other non-tumor-related abnormal regions during tumor evaluation.Therefore, we combined DWI with T1CE and to classify the imaging characteristics of such lesions, because it had better predictive efficiency and provided more comprehensive information about tumor characteristics.It had better predictive efficiency and provided more comprehensive information about tumor characteristics. This is consistent with a previous MR radiomics study on lung carcinoma classification[23] that reported that the best classification results were obtained for the multiparametric MRI data, with a mean AUC of 0.90 for classification between SCLC BMs and NSCLC BMs.Similarly, Li et al[24]conducted a multicenter study evaluating the feasibility of a deep learning approach based on multiparametric MRI to differentiate pathological subtypes of BMs in lung cancer patients,achieving AUC values of 0.796 and 0.751 in distinguishing SCLC from NSCLC BMs and differentiating AD from squamous cell carcinoma BMs.Tulum et al[25] successfully differentiated BMs from SCLC and NSCLC (AD and squamous cell carcinoma) in small datasets (74 patients) by introducing novel radiomic features with the sensitivity and specificity values of 94.44% and 95.33%,and deep learning algorithms with the values of 94.29% and 94.08%, basing on T2 weighted and FLAIR axial images, demonstrating the efficiency and importance of these methods in aiding the classification of lung cancer BMs, and indicating that the proposed novel radiomics feature algorithm had significant advantages over deep learning algorithms in identifying lung cancer subtypes in small datasets and exhibited strong interpretability. Compared to previous studies, our research capitalizes on a larger dataset utilizing multiparametric MRI radiomics, achieving AUCs of 0.762 and 0.861 in distinguishing SCLC from NSCLC and AD from NAD BMs, respectively. Highlighting the advantages of multiparametric MRI in this context, our approach offers superior clinical visualization and interpretability compared to deep learning models[26].
Previous studies have reported that models generated from radiomics provide promising results in differentiating pathological types of lung cancers based on BMs imaging[27]. Zhang et al[11] demonstrated the feasibility and accuracy of radiomics features extracted from brain-enhanced CT to identify the pathological subtypes of the primary site in the lung, achieving an AUC of 0.828 in the differentiation of primary lung adenocarcinoma and squamous cell carcinoma for patients with BMs. Although both MRI and CT are accepted as the primary modalities of screening for BMs, CT is markedly less sensitive than MRI and should be limited to patients with contraindications for MRI[28]. Li et al[12] reported that CT radiomics based lesion classification was highly specific in differentiating BMs of lung cancers, with misclassification rates of 3.1%, 4.3%, 5.8%, and 8.1%, for SCLC, squamous cell carcinoma, AD, and large cell lung carcinoma, respectively. They demonstrated that it was possible to differentiate BMs from SCLC and NSCLC using radiomics features extracted from T1CE images of brain metastatic lesions to predict the pathological subtypes of the originating lung cancers. This was consistent with our study, in which the predictive efficacy of the T1CE models was slightly better than that of the FLAIR and DWI models, possibly because T1CE is particularly useful for demonstrating vascularity within lesions of BMs[29]. Similarly, Ahn et al[30] proposed that T1CE image radiomics of BMs predicted the epidermal growth factor receptor (EGFR) mutation status of lung cancer BMs with good diagnostic performance, reaching an AUC of 89.09%. Thus, T1CE imaging has the potential to differentiate the pathological structure of tumors.T1CE not only facilitates the identification of lesion contours in BMs but also provides physicians with crucial information about lesion biology and treatment response[31]. Thus, MRI has the potential to differentiate the pathological structure of tumors and predict the pathological types of BMs in lung cancer[32].
There are some limitations in the current study. Firstly, this was a single-center study, with a relatively small sample size. Further, manual lesion segmentation may affect the generalizability of the model. To further improve classification efficacy and to assess the resulting clinical impact, multicenter studies are needed with standardized imaging protocols, standard post-processing procedures, and automatic tumor segmentation. Moreover, other subtypes of NSCLC, such as squamous cell carcinoma, adenosquamous and large cell lung carcinoma were excluded due to the limited number of cases available. The addition of basic clinical information (sex and age) may also help in improving the performance of the classifier models.