RECIST 1.1, mRECIST, and Choi criteria for evaluating treatment response and survival outcomes in hepatocellular carcinoma patients treated with atezolizumab plus bevacizumab.

OBJECTIVES: We aimed to compare the early responder rates, defined as complete or partial responders, using response evaluation criteria in solid tumors (RECIST) 1.1, modified RECIST (mRECIST), and Choi criteria in advanced HCC patients treated with atezolizumab-bevacizumab (atezo-bev), and to correlate them with progression-free survival (PFS) and overall survival (OS). METHODS: This retrospective study included advanced HCC patients treated with ≥ 3 cycles of atezo-bev. Two reviewers assessed responses using RECIST 1.1, mRECIST, and Choi criteria at 1st follow-up imaging. Kaplan-Meier curves with log-rank tests evaluated and compared PFS and OS. Cox proportional hazard models identified survival outcome predictors. Kappa statistics assessed inter-reader agreement. RESULTS: We evaluated 77 patients (65 men; mean age, 62.8 ± 12.3 years). Choi's criteria revealed the highest early responders rate (53.2%), exceeding mRECIST (32.5-33.8%) and RECIST 1.1 (24.7-26.0%), with an excellent agreement in all criteria (κ, 0.85-0.95). Across criteria, a consistent number of patients progressed (23-26) and was associated with significantly poor OS (ps ≤ 0.049). Responders by any criteria showed longer PFS (ps ≤ 0.009), and 1-year OS (ps ≤ 0.01). Choi criteria linked to significantly better OS without landmark (p = 0.003), with 1-year OS rates at 76.9% for responders vs 38.1% for non-responders. Cox analysis identified responders by Choi criteria as a significant OS predictor. CONCLUSION: Choi criteria identified more early responders than RECIST 1.1 and mRECIST, significantly correlating with improved OS. Choi criteria could be considered as a formal response assessment criterion for the emerging atezo-bev systemic treatment. CLINICAL RELEVANCE STATEMENT: For atezo-bev treatment of advanced HCC, more comprehensive response criteria, such as Choi criteria, could be effective in identifying early responders and predicting survival outcomes along with RECIST 1.1 and mRECIST. KEY POINTS: Choi criteria identified a higher rate of early responders compared to mRECIST and RECIST1.1 following atezo-bev treatment. Responders by all criteria had longer PFS and 1-year OS, and only those by Choi criteria experienced longer OS without landmark time. Choi criteria, with RECIST 1.1 and mRECIST, is an effective response assessment tool for atezo-bev treatment.

Deep learning-accelerated T2-weighted imaging versus conventional T2-weighted imaging in the female pelvic cavity: image quality and diagnostic performance.

BACKGROUND: The deep learning (DL)-based reconstruction algorithm reduces noise in magnetic resonance imaging (MRI), thereby enabling faster MRI acquisition. PURPOSE: To compare the image quality and diagnostic performance of conventional turbo spin-echo (TSE) T2-weighted (T2W) imaging with DL-accelerated sagittal T2W imaging in the female pelvic cavity. METHODS: This study evaluated 149 consecutive female pelvic MRI examinations, including conventional T2W imaging with TSE (acquisition time = 2:59) and DL-accelerated T2W imaging with breath hold (DL-BH) (1:05 [0:14 × 3 breath-holds]) in the sagittal plane. In 294 randomly ordered sagittal T2W images, two radiologists independently assessed image quality (sharpness, subjective noise, artifacts, and overall image quality), made a diagnosis for uterine leiomyomas, and scored diagnostic confidence. For the uterus and piriformis muscle, quantitative imaging analysis was also performed. Wilcoxon signed rank tests were used to compare the two sets of T2W images. RESULTS: In the qualitative analysis, DL-BH showed similar or significantly higher scores for all features than conventional T2W imaging (P <0.05). In the quantitative analysis, the noise in the uterus was lower in DL-BH, but the noise in the muscle was lower in conventional T2W imaging. In the uterus and muscle, the signal-to-noise ratio was significantly lower in DL-BH than in conventional T2W imaging (P <0.001). The diagnostic performance of the two sets of T2W images was not different for uterine leiomyoma. CONCLUSIONS: DL-accelerated sagittal T2W imaging obtained with three breath-holds demonstrated superior or comparable image quality to conventional T2W imaging with no significant difference in diagnostic performance for uterine leiomyomas.

Multidetector CT of Extrahepatic Bile Duct Cancer: Diagnostic Performance of Tumor Resectability and Interreader Agreement.

Background In extrahepatic bile duct (EHD) cancer, accurate assessment of resectability is essential for curative surgery, but pertinent guidelines from the perspectives of radiologists are yet to be developed. Purpose To investigate the performance of multiphasic CT in the assessment of longitudinal tumor extent, vascular invasion, and resectability of EHD cancer according to the Korean Society of Abdominal Radiology consensus recommendation and to evaluate the interreader agreement. Materials and Methods This retrospective study included patients with EHD cancer who underwent multiphasic CT examinations with section thickness of 3 mm or less before surgery from January 2016 to December 2018. Four abdominal radiologists independently evaluated the overall and biliary segment-wise longitudinal tumor extent, the presence of hepatic artery and/or portal vein invasion, and the resectability according to the Korean Society of Abdominal Radiology recommendations. The diagnostic performance was assessed with sensitivity, specificity, accuracy, and area under the receiver operating characteristic curve. Interreader agreement was determined using κ statistics. Results A total of 112 patients (mean age ± SD, 61 years ± 11; 73 men) were evaluated. The accuracy of the overall longitudinal tumor extent assessment ranged from 56.3% (63 of 112 patients) to 74.1% (83 of 112 patients). The sensitivity for detecting secondary confluence involvement (n = 62) was lower than that for the primary confluence or intrapancreatic duct (n = 115; 38.5%-75% vs 72.1%-96.3%, respectively). Vascular invasion (n = 17) had moderate sensitivity (28.6%-71.4%) and high specificity (77.5%-99.0%). For predicting negative-margin (R0) resection (n = 85), the sensitivity and specificity ranged from 71.8% to 96.5% and from 11.1% to 66.7%, respectively, and the areas under the receiver operating characteristic curve ranged from 0.69 to 0.80. Interreader agreements for tumor extent, vascular invasion, and resectability had κ values of 0.65-0.89, 0.21-0.64, and 0.35-0.56, respectively. Conclusion For the preoperative evaluation of extrahepatic bile duct cancer, the Korean Society of Abdominal Radiology consensus recommendation enabled systematic assessment of longitudinal tumor extent and vascular invasion with acceptable performance in predicting negative-margin resection with use of multiphasic CT and with fair to good interreader agreement. © RSNA, 2022 Online supplemental material is available for this article.

Identification of intratumoral fluid-containing area by magnetic resonance imaging to predict prognosis in patients with pancreatic ductal adenocarcinoma after curative resection.

OBJECTIVES: To compare the prognosis of pancreatic ductal adenocarcinoma (PDAC) after curative resection according to the type of intratumoral fluid-containing area identified on MRI. METHODS: This retrospective study included 112 consecutive patients who underwent upfront surgery with margin-negative resection between 2012 and 2019. All patients underwent MRI within 1 month before surgery. Three radiologists independently assessed the MRI findings, determined whether intratumoral fluid-containing areas were present, and classified all intratumoral fluid-containing areas by type (i.e., imaging necrosis or neoplastic mucin cysts). Recurrence-free survival (RFS) and overall survival (OS) were evaluated by the Kaplan-Meier method and the Cox proportional hazards model. Histopathological differences according to the type of intratumoral fluid-containing area were assessed. RESULTS: Of the 112 PDAC patients, intratumoral fluid-containing areas were identified on MRI in 33 (29.5%), among which 18 were classified as imaging necrosis and 15 as neoplastic mucin cysts. PDAC patients with imaging necrosis demonstrated significantly shorter RFS (mean 6.1 months versus 47.3 months; p < .001) and OS (18.4 months versus 55.0 months, p = .001) than those with neoplastic mucin cysts. Multivariable analysis showed that only the type of intratumoral fluid-containing area was significantly associated with RFS (hazard ratio, 2.25 and 0.38; p = .009 and p = .046 for imaging necrosis and neoplastic mucin cysts, respectively). PDAC with imaging necrosis had more frequent histological necrosis, more aggressive tumor differentiation, and higher tumor cellularity than PDAC with neoplastic mucin cysts (p ≤ .02). CONCLUSION: The detection and discrimination of intratumoral fluid-containing areas on preoperative MRI may be useful in predicting the prognosis of PDAC patients after curative resection. KEY POINTS: • Pancreatic ductal adenocarcinoma (PDAC) patients with imaging necrosis demonstrated significantly shorter survival than those with neoplastic mucin cysts after curative resection. • Multivariable analysis showed that only the type of intratumoral fluid-containing area identified on MRI was significantly associated with recurrence-free survival. • PDAC with imaging necrosis had more frequent histological necrosis, more aggressive tumor differentiation, and higher tumor cellularity than PDAC with neoplastic mucin cysts.

Predictive Value of Magnetic Resonance Imaging in Risk Stratification and Molecular Classification of Endometrial Cancer.

This study evaluated the magnetic resonance imaging (MRI) findings of endometrial cancer (EC) patients and identified differences based on risk group and molecular classification. The study involved a total of 175 EC patients. The MRI data were retrospectively reviewed and compared based on the risk of recurrence. Additionally, the associations between imaging phenotypes and genomic signatures were assessed. The low-risk and non-low-risk groups (intermediate, high-intermediate, high, metastatic) showed significant differences in tumor diameter (p < 0.001), signal intensity and heterogeneity on diffusion-weighted imaging (DWI) (p = 0.003), deep myometrial invasion (involvement of more than 50% of the myometrium), cervical invasion (p < 0.001), extrauterine extension (p = 0.002), and lymphadenopathy (p = 0.003). Greater diffusion restriction and more heterogeneity on DWI were exhibited in the non-low-risk group than in the low-risk group. Deep myometrial invasion, cervical invasion, extrauterine extension, lymphadenopathy, recurrence, and stage discrepancy were more common in the non-low-risk group (p < 0.001). A significant difference in microsatellite stability status was observed in the heterogeneity of the contrast-enhanced T1-weighted images (p = 0.027). However, no significant differences were found in MRI parameters related to TP53 mutation. MRI features can be valuable predictors for differentiating risk groups in patients with EC. However, further investigations are needed to explore the imaging markers based on molecular classification.

Validity of an automated screening Dixon technique for quantifying hepatic steatosis in living liver donors.

PURPOSE: This retrospective study aimed to evaluate the validity of an automated screening Dixon (e-DIXON) technique for quantifying hepatic steatosis in living liver-donor patients by comparison with magnetic resonance spectroscopy (MRS) as a reference standard. METHODS: A total of 285 living liver-donor candidates were examined with the e-DIXON technique and single-voxel MRS to assess hepatic steatosis and iron deposition between January 2014 and February 2019. The sensitivity, specificity, and positive and negative predictive values (PPV and NPV) of the e-DIXON technique for hepatic steatosis were calculated. The mean fat signal fractions obtained in MRS were compared between the donors diagnosed with hepatic steatosis and the normal group. The mean R2 values of donors with or without hepatic siderosis also were compared. RESULTS: The e-DIXON technique diagnosed normal in 133 (47%), fat in 124 (44%), iron in one (0.4%), and a combination of both fat and iron in 27 (10%) donors. The sensitivity, specificity, PPV, and NPV ​​for diagnosing hepatic steatosis were 94%, 70%, 64%, and 96%, respectively. There was a significant difference in the mean fat signal fraction obtained in MRS between the steatosis and normal groups (p < 0.001), but R2 values were not significantly different between siderosis and normal groups (p = 0.11). The e-DIXON technique showed a strong correlation with MRS in fat measurement (r2 = 0.92, p < 0.001). CONCLUSION: The e-DIXON technique reliably screens for hepatic steatosis but may not accurate for detecting hepatic iron deposition.

Differentiating Uterine Sarcoma From Atypical Leiomyoma on Preoperative Magnetic Resonance Imaging Using Logistic Regression Classifier: Added Value of Diffusion-Weighted Imaging-Based Quantitative Parameters.

OBJECTIVE: To evaluate the added value of diffusion-weighted imaging (DWI)-based quantitative parameters to distinguish uterine sarcomas from atypical leiomyomas on preoperative magnetic resonance imaging (MRI). MATERIALS AND METHODS: A total of 138 patients (age, 43.7 ± 10.3 years) with uterine sarcoma (n = 44) and atypical leiomyoma (n = 94) were retrospectively collected from four institutions. The cohort was randomly divided into training (84/138, 60.0%) and validation (54/138, 40.0%) sets. Two independent readers evaluated six qualitative MRI features and two DWI-based quantitative parameters for each index tumor. Multivariable logistic regression was used to identify the relevant qualitative MRI features. Diagnostic classifiers based on qualitative MRI features alone and in combination with DWI-based quantitative parameters were developed using a logistic regression algorithm. The diagnostic performance of the classifiers was evaluated using a cross-table analysis and calculation of the area under the receiver operating characteristic curve (AUC). RESULTS: Mean apparent diffusion coefficient value of uterine sarcoma was lower than that of atypical leiomyoma (mean ± standard deviation, 0.94 ± 0.30 10-3 mm²/s vs. 1.23 ± 0.25 10-3 mm²/s; P < 0.001), and the relative contrast ratio was higher in the uterine sarcoma (8.16 ± 2.94 vs. 4.19 ± 2.66; P < 0.001). Selected qualitative MRI features included ill-defined margin (adjusted odds ratio [aOR], 17.9; 95% confidence interval [CI], 1.41-503, P = 0.040), intratumoral hemorrhage (aOR, 27.3; 95% CI, 3.74-596, P = 0.006), and absence of T2 dark area (aOR, 83.5; 95% CI, 12.4-1916, P < 0.001). The classifier that combined qualitative MRI features and DWI-based quantitative parameters showed significantly better performance than without DWI-based parameters in the validation set (AUC, 0.92 vs. 0.78; P < 0.001). CONCLUSION: The addition of DWI-based quantitative parameters to qualitative MRI features improved the diagnostic performance of the logistic regression classifier in differentiating uterine sarcomas from atypical leiomyomas on preoperative MRI.

Predicting resection margin status of pancreatic neuroendocrine tumors on CT: performance of NCCN resectability criteria.

OBJECTIVE: To test the performance of the National Comprehensive Cancer Network (NCCN) CT resectability criteria for predicting the surgical margin status of pancreatic neuroendocrine tumor (PNET) and to identify factors associated with margin-positive resection. METHODS: Eighty patients with pre-operative CT and upfront surgery were retrospectively enrolled. Two radiologists assessed the CT resectability (resectable [R], borderline resectable [BR], unresectable [UR]) of the PNET according to NCCN criteria. Logistic regression was used to identify factors associated with resection margin status. κ statistics were used to evaluate interreader agreements. Kaplan-Meier method with log-rank test was used to estimate and compare recurrence-free survival (RFS). RESULTS: Forty-five patients (56.2%) received R0 resection and 35 (43.8%) received R1 or R2 resection. R0 resection rates were 63.6-64.2%, 20.0-33.3%, and 0% for R, BR, and UR diseases, respectively (all p ≤ 0.002), with a good interreader agreement (κ, 0.74). Tumor size (<2 cm, 2-4 cm, and >4 cm; odds ratio (OR), 9.042-18.110; all p ≤ 0.007) and NCCN BR/UR diseases (OR, 5.918; p = 0.032) were predictors for R1 or R2 resection. The R0 resection rate was 91.7% for R disease <2 cm and decreased for larger R disease. R0 resection and smaller tumor size in R disease improved RFS. CONCLUSION: NCCN resectability criteria can stratify patients with PNET into distinct groups of R0 resectability. Adding tumor size to R disease substantially improves the prediction of R0 resection, especially for PNETs <2 cm. ADVANCES IN KNOWLEDGE: Tumor size and radiologic resectability independently predicted margin status of PNETs.

Deep Learning-Accelerated Liver Diffusion-Weighted Imaging: Intraindividual Comparison and Additional Phantom Study of Free-Breathing and Respiratory-Triggering Acquisitions.

OBJECTIVES: Deep learning-reconstructed diffusion-weighted imaging (DL-DWI) is an emerging promising time-efficient method for liver evaluation, but analyses regarding different motion compensation strategies are lacking. This study evaluated the qualitative and quantitative features, sensitivity for focal lesion detection, and scan time of free-breathing (FB) DL-DWI and respiratory-triggered (RT) DL-DWI compared with RT conventional DWI (C-DWI) in the liver and a phantom. MATERIALS AND METHODS: Eighty-six patients indicated for liver MRI underwent RT C-DWI, FB DL-DWI, and RT DL-DWI with matching imaging parameters other than the parallel imaging factor and number of averages. Two abdominal radiologists independently assessed qualitative features (structural sharpness, image noise, artifacts, and overall image quality) using a 5-point scale. The signal-to-noise ratio (SNR) along with the apparent diffusion coefficient (ADC) value and its standard deviation (SD) were measured in the liver parenchyma and a dedicated diffusion phantom. For focal lesions, per-lesion sensitivity, conspicuity score, SNR, and ADC value were evaluated. Wilcoxon signed rank test and repeated-measures analysis of variance with post hoc test revealed the difference in DWI sequences. RESULTS: Compared with RT C-DWI, the scan times for FB DL-DWI and RT DL-DWI were reduced by 61.5% and 23.9%, respectively, with statistically significant differences between all 3 pairs (all P 's < 0.001). Respiratory-triggered DL-DWI showed a significantly sharper liver margin, less image noise, and more minor cardiac motion artifact compared with RT C-DWI (all P 's < 0.001), whereas FB DL-DWI showed more blurred liver margins and poorer intrahepatic vessels demarcation than RT C-DWI. Both FB- and RT DL-DWI showed significantly higher SNRs than RT C-DWI in all liver segments (all P 's < 0.001). There was no significant difference in overall ADC values across DWI sequences in the patient or phantom, with the highest value recorded in the left liver dome by RT C-DWI. The overall SD was significantly lower with FB DL-DWI and RT DL-DWI than RT C-DWI (all P 's ≤ 0.003). Respiratory-triggered DL-DWI showed a similar per-lesion sensitivity (0.96; 95% confidence interval, 0.90-0.99) and conspicuity score to those of RT C-DWI and significantly higher SNR and contrast-to-noise ratio values ( P ≤ 0.006). The per-lesion sensitivity of FB DL-DWI (0.91; 95% confidence interval, 0.85-0.95) was significantly lower than that of RT C-DWI ( P = 0.001), with a significantly lower conspicuity score. CONCLUSIONS: Compared with RT C-DWI, RT DL-DWI demonstrated superior SNR, comparable sensitivity for focal hepatic lesions, and reduced acquisition time, making it a suitable alternative to RT C-DWI. Despite FB DL-DWI's weakness in motion-related challenges, further refinement could potentiate FB DL-DWI in the context of abbreviated screening protocols, where time efficiency is a high priority.

Unenhanced computed tomography for non-invasive diagnosis of hepatic steatosis with low tube potential protocol.

BACKGROUND: Lowering kVp affects the image contrast and computed tomography (CT) attenuation values of low kVp CT is different from those of conventional 120-kVp scans. The purpose of this study is to determine the diagnostic performance and to establish the reference range of low-kVp unenhanced CT for the assessment of hepatic steatosis in liver transplantation donors using magnetic resonance (MR) spectroscopy as a reference standard. METHODS: This retrospective study included 165 potential donors (male:female =114:51, 36.5±12.0 years old) who underwent 100-kVp single-slice unenhanced CT scan and MR spectroscopy. The difference between hepatic and splenic attenuation (CTL-S) and liver-to-spleen attenuation ratio (CTL/S) were calculated. Reference standard was the fat signal fraction measured by MR spectroscopy. Limits of agreement between CT measurements and the reference standard were calculated. Areas under receiver operating characteristic curves (AUROCs) of CTL-S and CTL/S were compared for the diagnosis of moderate to severe steatosis. Cut-off values of CTL-S and CTL/S that provided a balance between sensitivity and specificity and the highest specificity using the lower limit of the reference range were calculated. RESULTS: Eighty-seven subjects had a non-steatotic liver. Sixty-one subjects had mild steatosis and 17 subjects had moderate to severe steatosis based on MR spectroscopy. CTL-S and CTL/S values were negatively correlated with the fat signal fraction (P<0.001) and limits of agreement were -8.4% to 8.4% for CTL-S and -9.6% to 9.6% for CTL/S. AUROCs of CTL-S and CTL/S for diagnosing moderate to severe steatosis were 0.956 and 0.957, respectively. Cut-off values of CTL-S and CTL/S for diagnosis of moderate to severe steatosis by the Youden index were -0.5 HU for CTL-S and 0.99 for CTL/S. Reference ranges of non-steatotic liver were -6.90 to 31.40 HU for CTL-S and 0.89 to 1.77 for CTL/S. Using -6.9 HU for CTL-S and 0.89 for CTL/S as cut-off values, the sensitivity and specificity for diagnosing moderate to severe steatosis were 70.59% and 90.54% (CTL-S) and 76.47% and 90.54% (CTL/S), respectively. CONCLUSIONS: Measurements from a low-kVp unenhanced CT scan were negatively correlated with the degree of hepatic steatosis. Low-kVp unenhanced CT is a robust technique with reduced radiation exposure for diagnosing moderate to severe hepatic steatosis.

Survival Prediction after Curative Resection of Pancreatic Ductal Adenocarcinoma by Imaging-Based Intratumoral Necrosis.

We aimed to determine the histopathological characteristics and prognosis of curatively resected pancreatic ductal adenocarcinoma (PDAC) showing intratumoral necrosis on preoperative CT or MRI. This study consecutively included 102 patients who underwent upfront surgery with margin-negative resection from 2012 to 2020. All patients underwent both pancreatic CT and MRI within 1 month before surgery. Two radiologists independently assessed CT/MRI findings, including the presence of CT- and MRI-detected necrosis. Histopathological characteristics of PDACs according to CT or MRI detection of necrosis were evaluated. Disease-free survival (DFS) and overall survival (OS) were assessed by the Kaplan−Meier method and the Cox proportional hazards model. Among the 102 PDAC patients, 14 patients (13.7%) had CT-detected necrosis, and 16 patients (15.7%) had MRI-detected necrosis, of which 9 showed both CT- and MRI-detected necrosis. PDACs with CT- or MRI-detected necrosis demonstrated a significantly higher degree of histopathological necrosis than those without (p < 0.001). Multivariable analysis revealed that tumor size (hazard ratio [HR], 1.19; p = 0.040), tumor location (HR, 0.46; p = 0.009), and MRI-detected necrosis (HR, 2.64; p = 0.002) had independent associations with DFS. Only MRI-detected necrosis was significantly associated with OS (HR, 2.59; p = 0.004). Therefore, MRI-detected necrosis might be a potential imaging predictor of poor survival after curative resection of PDAC.

Diagnostic Performance of KLCA-NCC 2018 Criteria for Hepatocellular Carcinoma Using Magnetic Resonance Imaging: A Systematic Review and Meta-Analysis.

Several imaging-based systems have been proposed for the diagnosis of hepatocellular carcinoma (HCC) using magnetic resonance imaging (MRI), reflecting geographical differences in the clinical environment for HCC. We conducted a systematic review and meta-analysis to determine the performance of the Korean Liver Cancer Association-National Cancer Center (KLCA-NCC) 2018 criteria for the MRI diagnosis of HCC. Original studies reporting the performance of the KLCA-NCC 2018 criteria for the diagnosis of HCC using MRI were identified in MEDLINE and EMBASE until 29 March 2021. The meta-analytic pooled sensitivity and specificity of the KLCA-NCC 2018 criteria for diagnosing HCC were calculated using a bivariate random-effects model. A meta-regression analysis was performed to explore study heterogeneity further. Eight studies involving 1690 HCCs reported the accuracy of the KLCA-NCC 2018 imaging criteria. The pooled sensitivity and specificity of the definite HCC criteria for diagnosing HCC were 81% (95% confidence interval, 76-85%; I2 = 86%) and 90% (86-93%; I2 = 23%), respectively. For five available studies, the pooled sensitivity and specificity of the definite HCC criteria for diagnosing HCCs smaller than 20 mm were 80% (72-86%; I2 = 76%) and 91% (86-94%; I2 = 0%), respectively. A considerable threshold effect with a correlation coefficient of 0.667 was observed. The results of the meta-regression analysis revealed that the accuracy of the definite HCC criteria differed significantly depending on the type of MRI contrast agent (p = 0.01). In conclusion, the KLCA-NCC 2018 criteria had good overall diagnostic performance in diagnosing HCC. Substantial study heterogeneity was observed for sensitivity, which was significantly influenced by the type of contrast agent and by a threshold effect.

Coronary-to-Pulmonary Artery Fistula in Adults: Natural History and Management Strategies.

OBJECTIVE: To evaluate the natural course of coronary-to-pulmonary artery fistula (CPAF) detected on coronary computed tomography angiography (CCTA) and to propose potential treatment strategies. MATERIALS AND METHODS: In this retrospective multicenter study, we assessed the CCTA reports of 188 CPAF patients evaluated between March 2009 and June 2016. Fifty-seven patients were excluded because their follow-up (FU) periods were less than 2 years. Information regarding demographic characteristics, past history, treatment method, and the occurrence of major adverse cardiac events (MACE) during the FU period was collected. We analyzed the morphologic features of CPAF and the various factors associated with surgical treatment. Patients who had undergone FU CCTA after being diagnosed with CPAF were assessed for the presence of morphological changes on FU imaging. RESULTS: The median age of the study population was 63.0 years (range, 57.0-72.0 years), and the median FU period was 5.72 years (range, 4.08-6.96 years). The most common origin of the CPAF was both coronary arteries in 76 (58.0%) cases. An aneurysm or aneurysms was/were present in 41 (31.3%) cases. Fifty-four (41.2%) fistulas were less than 2 mm in size. Eight patients underwent surgery, and 123 (93.9%) patients received optimal medical treatment (OMT). The fistula size was significantly different between the two treatment groups (p = 0.013) and was the only factor associated with surgical treatment (odds ratio = 1.14, p = 0.021). Only one patient in the OMT group reported MACE during the FU period due to preexisting coronary artery disease. Twenty-nine patients (22.1%) underwent FU CCTA after CPAF diagnosis, with a median FU period of 3.81 years. None of the patients in the OMT group demonstrated morphological changes in the CPAF on FU imaging. CONCLUSION: Most CPAFs identified on CCTA have a favorable prognosis. Observation with OMT is usually an appropriate strategy. Fistula size is a possible determinant for surgical treatment.