Advances in pediatric oncology MRI

Acute adverse reactions after multiple initially well-tolerated gadolinium-based contrast-enhanced abdomen MRIs in pediatric patients

PURPOSE

Repeated gadolinium-based contrast agent (GBCA)-enhanced MRIs are crucial in the diagnosis and follow-up of oncologic and chronic disorders in pediatric patients. The aim of the study was to evaluate the frequency and severity of adverse reactions to GBCAs in children after a single vs. multiple GBCA-enhanced abdomen MRIs.

MATERIAL AND METHODS

All pediatric patients with at least one GBCA-enhanced abdominal MRI between 2009 and 2020 were retrospectively evaluated based on adverse reactions reports, according to the classification system of the American College of Radiology and guidelines on contrast agents of the European Society of Urogenital Radiology. A Student´s t-test analysis, a spearman ρ-correlation and a Chi-square test between the reported adverse reactions and the total number of GBCA applications, and the number of each applied GBCA was calculated. A p-value <0.05 was considered significant.

RESULTS

Of 623 patients with 964 GBCA-enhanced abdomen MRIs, there were 464 patients with only one and 159 patients with multiple GBCA administrations. Of 964 GBCA doses administrated, two cases with urticaria (mild allergy-like adverse reaction) and one case with vomiting (mild chemotoxic adverse reaction) were recorded (3/964 = 0.31%), but all the reports were in patients with multiple GBCA administration (3/159 = 1.89%). No adverse reactions in patients with a single GBCA administration were observed. The reported adverse reactions correlated significantly with the total number of GBCAs (p<0.001) and the number of each GBCA (p<0.001 or p = 0.002). The independent two-tailed t-tests, and the chi-square test were significant (p<0.001, p = 0.003).

CONCLUSION

GBCA-associated adverse reactions are rare and mostly mild, but initially well-tolerated GBCA could cause adverse reactions due to the increase likelihood of drug hypersensitivity upon repeated GBCA exposure.

Influence of age on gadoxetic acid disodium-induced transient respiratory motion artifacts in pediatric liver MRI

PURPOSE

Gd-EOB-DTPA-enhanced liver MRI is frequently compromised by transient severe motion artifacts (TSM) in the arterial phase, which limits image interpretation for the detection and differentiation of focal liver lesions and for the recognition of the arterial vasculature before and after liver transplantation. The purpose of this study was to investigate which patient factors affect TSM in children who undergo Gd-EOB-DTPA-enhanced liver MRI and whether younger children are affected as much as adolescents.

METHODS

One hundred and forty-eight patients (65 female, 83 male, 0.1-18.9 years old), who underwent 226 Gd-EOB-DTPA-enhanced MRIs were included retrospectively in this single-center study. The occurrence of TSM was assessed by three readers using a four-point Likert scale. The relation to age, gender, body mass index, indication for MRI, requirement for sedation, and MR repetition was investigated using uni- and multivariate logistic regression analysis.

RESULTS

In Gd-EOB-DTPA-enhanced MRIs, TSM occurred in 24 examinations (10.6%). Patients with TSM were significantly older than patients without TSM (median 14.3 years; range 10.1-18.1 vs. 12.4 years; range 0.1-18.9, p<0.001). TSM never appeared under sedation. Thirty of 50 scans in patients younger than 10 years were without sedation. TSM were not observed in non-sedated patients younger than 10 years of age (p = 0.028). In a logistic regression analysis, age remained the only cofactor independently associated with the occurrence of TSM (hazard ratio 9.152, p = 0.049).

CONCLUSION

TSM in Gd-EOB-DTPA-enhanced liver MRI do not appear in children under the age of 10 years.

Importance of whole-body imaging with complete coverage of hands and feet in alveolar rhabdomyosarcoma staging

BACKGROUND

Alveolar rhabdomyosarcoma commonly arises in the extremities and is characterized by aggressive biology and high frequency of metastases. Whole-body imaging is increasingly employed in pediatric oncology but not recommended as standard in the staging of soft-tissue sarcomas.

OBJECTIVE

After observing patients with a large symptomatic alveolar rhabdomyosarcoma lesion and a smaller silent lesion in the more distal part of an extremity we sought to estimate the frequency of this constellation.

MATERIALS AND METHODS

We retrospectively evaluated the data of prospectively registered paediatric patients (age <21 years) with alveolar rhabdomyosarcoma in the SoTiSaR (Soft Tissue Sarcoma Registry) of the Cooperative Weichteilsarkom Studiengruppe (CWS) 09/2011-04/2015 with regard to whole-body imaging.

RESULTS

Seventy-five patients were eligible. Images of 57 patients had been submitted for reference consultation, including 80 whole-body examinations in 36 patients. Among them were 5 patients (14%, 95% confidence interval 3-25%) who had been diagnosed because of a symptomatic lesion while an additional silent lesion in the distal part of an extremity had remained unnoticed and had only been detected by later whole-body imaging. It is noteworthy that in 42 (53%) of all 80 whole-body examinations, the hands and feet had been only partially covered or completely excluded.

CONCLUSION

In alveolar rhabdomyosarcoma silent lesions can be overlooked when the distal parts of the limbs are not thoroughly examined and not completely covered by imaging. Missing them influences treatment decisions and prognosis. Our results should be considered when evaluating the potential role of whole-body imaging in rhabdomyosarcoma.

Accuracy of pre-contrast imaging in abdominal magnetic resonance imaging of pediatric oncology patients

BACKGROUND

Safety concerns are increasingly raised regarding the use of gadolinium-based contrast media for MR imaging.

OBJECTIVE

To determine the accuracy of pre-contrast abdominal MR imaging for lesion detection and characterization in pediatric oncology patients.

MATERIALS AND METHODS

We included 120 children (37 boys and 83 girls; mean age 8.94 years) referred by oncology services. Twenty-five had MRI for the first time and 95 were follow-up scans. Two authors independently reviewed pre-contrast MR images to note the following information about the lesions: location, number, solid vs. cystic and likely nature. Pre- and post-contrast imaging reviewed together served as the reference standard.

RESULTS

The overall sensitivity was 88% for the first reader and 90% for the second; specificity was 94% and 91%; positive predictive value was 96% and 94%; negative predictive value was 82% and 84%; accuracy of pre-contrast imaging for lesion detection as compared to the reference standard was 90% for both readers. The difference between mean number of lesions detected on pre-contrast imaging and reference standard was not significant for either reader (reader 1, P = 0.072; reader 2, P = 0.071). There was substantial agreement (kappa values of 0.76 and 0.72 for readers 1 and 2) between pre-contrast imaging and reference standard for determining solid vs. cystic lesion and likely nature of the lesion. The addition of post-contrast imaging increased confidence of both readers significantly (P < 0.0001), but the interobserver agreement for the change in confidence was poor (kappa 0.12).

CONCLUSION

Pre-contrast abdominal MR imaging has high accuracy in lesion detection in pediatric oncology patients and shows substantial agreement with the reference standard for characterization of lesions. Gadolinium-based contrast media administration cannot be completely eliminated but can be avoided in many cases, with the decision made on a case-by-case basis, taking into consideration location and type of tumor.

Establishment of a lung metastatic breast tumor xenograft model in nude rats

Objective

Larger animal models provide relevant tumor burden in the development of advanced clinical imaging methods for non-invasive cancer detection and diagnosis, and are especially valuable for studying metastatic disease. Most available experimental models, however, are based on immune-compromised mice. To lay the foundation for studying spontaneous metastasis using non-invasive magnetic resonance imaging (MRI), this study aims to establish a highly metastatic breast cancer xenograft model in nude rats.

Materials and Methods

A highly metastatic variant of human adenocarcinoma MDA-MB-231 known as LM2 was inoculated into nude rats. Orthotopic and subcutaneous (flank) sites were compared, with half of the orthotopic injections guided by ultrasound imaging. MRI with gadolinium contrast administration was performed weekly beginning on Day 6 and ending on Day 104. Excised tumors were assessed on histology using hematoxylin and eosin and CD34. Fisher's exact test was used to compare successful tumor induction amongst different inoculation methods.

Results

Primary LM2 tumors were established orthotopically in all cases under ultrasound-guided injection, and none otherwise (p = 0.0028). Contrast-enhanced MRI revealed rapidly progressing tumors that reached critical size (15 mm diameter) in 2 to 3 weeks after inoculation. MRI and histology findings were consistent: LM2 tumors were characterized by low vascularity confined to the tumor rim and large necrotic cores with increasing interstitial fluid pressure.

Conclusions

The metastatic LM2 breast tumor model was successfully established in the mammary fat pads of nude rats, using ultrasound needle guidance as a non-invasive alternative to surgery. This platform lays the foundation for future development and application of MRI to study spontaneous metastasis and different stages throughout the metastatic cascade.