Study Patients
This two-center retrospective study protocol was approved by the institutional review board (2018ZDSYLL162-P01) and the requirement of the informed consent was waived due to the retrospective nature of the study. The diagnosis of HCC was based on the criteria of the American Association for the Study of Liver Disease [17]. The workflow of the study design and patient selection was depicted in Fig. 1.
The inclusion criteria for the recruited data were as follows: (a) contrast-enhanced liver MRI performed within two weeks before treatment; (b) data of both clinical laboratory test and MRI; (c) images with an acceptable quality for quantitative analysis; (d) no previous treatment for HCC at the time of liver MRI scan; and (e) no comorbid diseases, such as other tumors, pancreatitis, acute cholecystitis, severe cirrhosis, severe fatty liver and massive ascites. Eligible cases were divided into three cohorts, i.e., the training cohort with patients scanned at one Institution A from May 2015 to March 2020 (n = 279); the internal validation cohort with patients scanned at the same institution from April 2020 to May 2021 (n = 120); and the external validation cohort with patients scanned in a different Institution B from January 2014 to June 2021(n = 90).
Data collection
Demographic data, including age, sex, height, and body weight at time of HCC diagnosis, were obtained from the database of clinical records. Patients were followed up for changes in body weight for six months, with body mass index (BMI) calculated for each patient. BMI was categorized according to the guidelines by the World Health Organization for Asian: underweight, below 18.5 kg/m2; normal weight, 18.5-<23 kg/m2; overweight, 23.0-<25 kg/m2; and obese, above 25 kg/m2. We also collected the degree of liver dysfunction (Child-Pugh class), Barcelona Clinic Liver Cancer (BCLC) stage, and the causes of chronic liver disease. The results from laboratory tests included bilirubin, albumin, aspartate transaminase, alanine transaminase, platelet, prothrombin time, the international normalized ratio of prothrombin time, serum α-fetoprotein (AFP) level, and serum carbohydrate antigen 19 − 9 level.
The enrolled patients received different forms of treatment in their standard clinical care. For patients who underwent multiple HCC treatments, the treatments were ranked as surgical resection, local ablation (radiofrequency or microwave ablation), stereotactic body radiotherapy, transarterial chemoembolization or radioembolization, systemic therapy, best supportive care, with one preceding another in accordance with the stages of disease progression [18], which may facilitate the counting of each treatment type and exploration of the impact of treatments on this study.
According to the international consensus [1], cachexia was diagnosed when HCC patients reported a weight loss of more than 5% over six months without diet management, or a BMI of less than 20 kg/m2 and a weight loss of more than 2%.
MRI Data Acquisition and Image Analysis
All patients underwent abdominal multiparametric contrast-enhanced MRI scan on a 3.0-T MR scanner (TrioTim, Siemens Medical Solutions, Erlangen, Germany; Discovery MR750, GE Healthcare, Milwaukee, USA; Ingenia, Philips Medical Systems, Best, The Netherlands; MEGNETOM Vida, Siemens Medical Solutions, Erlangen, Germany). When the contrast-enhanced MRI was perfomed, patients were intravenously injected at 1 mL/sec with either gadopentetate dimeglumine (Magnevist; Bayer) at a dose of 0.2 mL/kg (n = 249) or gadoxetic acid disodium (Primovist; Bayer) at a dose of 0.1 mL/kg (n = 240), followed by a saline wash (20 mL). MRI protocols routinely involved dual-echo spoiled gradient-echo T1-weighted in phase and out of phase imaging, T2-weighted fast spin echo imaging, diffusion-weighted imaging using b-values of 0 and 800 s/mm2, and dynamic fat-suppressed 3D T1-weighted gradient-echo imaging. T1-weighted dynamic contrast-enhanced imaging was performed before and after the intravenous injection of the contrast agent. Briefly, after the contrast injection, consecutive contrast-enhanced dynamic images were acquired in the arterial phase (25–30 seconds), early portal venous phase (60–75 seconds), late portal venous phase (95–105 seconds), delayed/transitional phase (2–5 minutes), or hepatobiliary phase (15–20 minutes). The equipment, imaging sequences, and parameters used for liver MRI are summarized in Supplementary Table S1.
All liver images were read and interpreted by three experienced radiologists. The images collected from Institution A were reviewed by two independent radiologists (AA and AA) and those from Institution B by another two radiologists (AA and AA). In case of disagreement between the two radiologists, a joint review was conducted to obtain a consensus for the final report. All readers were blinded to the clinical diagnosis of cachexia and laboratory test results. The number of visible lesions, size of the lesion, and the presence or absence of the portal vein tumor thrombus, and extrahepatic metastasis were recorded for each patient.
In addition, readers assessed the presence or absence of other radiological findings of the tumors, including heterogeneity, necrosis, blood products in mass, intralesional fat, tumor capsule, hepatic capsular retraction, corona enhancement, nodule-in-nodule, mosaic architecture, intratumoral artery, nonperipheral washout, and restricted diffusion. Evaluattions were also made for the imaging findings of the signal intensity of tumors on the pre-contrast T1-weighted imaging (T1WI), T2-weighed imaging (T2WI), and those during the delayed or transitional phase, the presence or absence of ill-defined tumor margin, rim arterial phase hyperenhancement, and arterial phase peritumoral enhancement. In case of multiple lesions, only the largest one (main lesion) on the MRI scan was analyzed. The detailed descriptions of MRI findings identified and used in the study are summarized in the Supplementary information.
Statistical Analysis
All statistical analyses were performed using IBM SPSS Statistics (Version 26.0) and R software (version 4.2.2, http://www.r-project.org). The “rms” package was used to construct nomogram and calibration curve. The “pROC” and “rmda” packages were used to analyze the receiver-operator characteristic (ROC) and decision curve analysis (DCA) curves, respectively. A two-tailed P value of < 0.05 was considered statistically significant for the comparison of the area under the curve (AUC) of the ROC. Continuous variables were expressed as mean ± standard deviation or as median and interquartile range. Variables were expressed as odds ratio (OR) and 95% confidence intervals (CI).
The inter-observer agreement for each selected MRI feature or descriptor was evaluated by the κ statistic for categorical variables and intraclass correlation coefficient for continuous variables. The strength of the agreement is shown in Supplementary information.
For data from the training cohort, univariable and multivariable logistic regression analyses were performed to determine the MRI features and clinical laboratory indexes that significantly contributed to the correlation with clinically-confirmed cachexia. Variables with a P value of less than 0.10 in the univariable analysis were entered into the multivariable analysis, which produced a clinical data only model, an imaging feature model, and a combined model in a stepwise backward process. The predictive performances of the three models were assessed by the levels of discrimination and calibration. The nomogram was constructed with the inputs from the model with the best performance. The sensitivity and specificity of the models were also calculated. For the risk assessment of possible cachexia in each patient, the total points of each selected clinical and imaging feature were calculated with the logistic regression coefficients in the multivariable analysis by Eq. (1):
Points = β0 + β1X1 + β2X2 + … + βnXn (1)
in which β0 is the constant, βn is the logistic regression coefficients, and Xn is the value of found for clinical or imaging features.
The level of discrimination by the nomogram was determined by the AUC of ROC. The quality of calibration was assessed by the calibration curve, which indicates the consistency between the predicted and observed risks of cachexia.
Stratification analysis was conducted for the type of treatment, type of contrast agents, and version of MRI system via AUC comparison by the Delong test. The DCA was used to evaluate the clinical efficacy of the obtained nomogram according to the net benefit at different threshold probabilities (0-100%), when the three models were compared with the strategy assumption of the diagnosis-all scheme (ALL) or the diagnosis-none scheme (NONE).