Radiologic Response Assessment in Pediatric Soft Tissue Sarcoma: Computed-Assisted Volume Evaluation

Role of Imaging in Initial Prognostication of Locally Advanced Soft Tissue Sarcomas

BACKGROUND

Although imaging is central in the initial staging of patients with soft tissue sarcomas (STS), it remains underused and few radiological features are currently used in practice for prognostication and to help guide the best therapeutic strategy. Yet, several prognostic qualitative and quantitative characteristics from magnetic resonance imaging (MRI) and positron emission tomography (PET) have been identified over these last decades.

OBJECTIVE

After an overview of the current validated prognostic features based on baseline imaging and their integration into prognostic tools, such as nomograms used by clinicians, the aim of this review is to summarize more complex and innovative MRI, PET, and radiomics features, and to highlight their role to predict indirectly (through histologic grade) or directly the patients' outcomes.

GEIS-SEHOP clinical practice guidelines for the treatment of rhabdomyosarcoma

Rhabdomyosarcoma (RMS) is the most frequent soft tissue sarcoma (STS) in children and adolescents. In Spain the annual incidence is 4.4 cases per million children < 14 years. It is an uncommon neoplasm in adults, but 40% of RMS are diagnosed in patients over 20 years of age, representing 1% of all STS in this age group. RMS can appear anywhere in the body, with some sites more frequently affected including head and neck, genitourinary system and limbs. Assessment of a patient with suspicion of RMS includes imaging studies (MRI, CT, PET-CT) and biopsy. All patients with RMS should receive chemotherapy, either at diagnosis in advanced or metastatic stages, or after initial resection in early local stages. Local control includes surgery and/or radiotherapy depending on site, stage, histology and response to chemotherapy. This guide provides recommendations for diagnosis, staging and treatment of this neoplasm.

Pediatric Rhabdomyosarcomas: Three-Dimensional Radiological Assessments after Induction Chemotherapy Predict Survival Better than One-Dimensional and Two-Dimensional Measurements

Radiological response to neoadjuvant chemotherapy is currently used to assess the efficacy of treatment in pediatric patients with rhabdomyosarcoma (RMS), but the association between early tumor response on imaging and survival is still controversial. The aim of this study was to investigate the prognostic value of assessing radiological response after induction therapy in pediatric RMS, comparing four different methods. This retrospective, two-center study was conducted on 66 non-metastatic RMS patients. Two radiologists measured tumor size on pre- and post-treatment magnetic resonance (MR) or computed tomography (CT) images using four methods: considering maximal diameter with the 1D-RECIST (Response Evaluation Criteria in Solid Tumors); multiplying the two maximal diameters with the 2D-WHO (World Health Organization); multiplying the three maximal diameters with the 3D-EpSSG (European pediatric Soft tissue sarcoma Study Group); obtaining a software-assisted volume assessment with the 3D-Osirix. Each patient was classified as a responder or non-responder based on the proposed thresholds for each method. Tumor response was compared with survival using Kaplan-Meier plots, the log-rank test, and Cox's regression. Agreement between methods and observers (weighted-κ) was also calculated. The 5-year event-free survival (5yr-EFS) calculated with the Kaplan-Meier plots was significantly longer for responders than for non-responders with all the methods, but the 3D assessments differentiated between the two groups better than the 1D-RECIST or 2D-WHO (p_1D-RECIST = 0.018, p_2D-WHO = 0.007, p_3D-EpSSG and p_3D-Osirix < 0.0001). Comparing the 5yr-EFS of responders and non-responders also produced adjusted hazard ratios of 3.57 (p = 0.0158) for the 1D-RECIST, 5.05 for the 2D-WHO (p = 0.0042), 14.40 for the 3D-EpSSG (p < 0.0001) and 11.60 for the 3D-Osirix (p < 0.0001), indicating that the volumetric measurements were significantly more strongly associated with EFS. Inter-method agreement was excellent between the 3D-EpSSG and the 3D-Osirix (κ = 0.98), and moderate for the other comparisons (0.5 < κ < 0.8). The 1D-RECIST and the 2D-WHO tended to underestimate response to treatment. Inter-observer agreement was excellent with all methods (κ > 0.8) except for the 2D-WHO (κ = 0.7). In conclusion, early tumor response was confirmed as a significant prognostic factor in RMS, and the 3D-EpSSG and 3D-Osirix methods predicted response to treatment better than the 1D-RECIST or 2D-WHO measurements.

MRI of Rhabdomyosarcoma and Other Soft-Tissue Sarcomas in Children

Soft-tissue sarcomas in children comprise a heterogeneous group of entities with variable manifestation depending on the age of the patient and the location of the tumor. MRI is the modality of choice for evaluating musculoskeletal soft-tissue tumors and plays a paramount role in both initial diagnosis and assessment of tumor response during and after treatment. Conventional MRI sequences, such as T1- and T2-weighted imaging, offer morphologic information, which is important for localizing the lesion and describing anatomic relationships but not accurate for determining its malignant or benign nature and may be limited in differentiating tumor response from therapy-related changes. Advanced multiparametric MRI offers further functional information that can help with these tasks by using different imaging sequences and biomarkers. The authors present the role of MRI in rhabdomyosarcoma and other soft-tissue sarcomas in children, emphasizing a multiparametric approach with focus on the utility and potential added value of diffusion-weighted imaging (DWI) and dynamic contrast-enhanced MRI in characterization and staging, determination of pretreatment extent, and evaluation of tumor response and recurrence after treatment. ^©RSNA, 2020.

The medico-legal assessment of aesthetic damage. A correlation analysis between experts and an operative proposal

Aesthetic damage, defined as any detrimental modification of the individual morpho-functional exterior attributes, is difficult to assess, since the perception of its entity is rather subjective. This study aims to provide a medico-legal contribution to the assessment of this kind of damage. 60 photographic images, representing stabilized aesthetic damage, were collected and showed to 16 expert evaluators, who were required to exclusively quantify the objective component of the aesthetic impairment. The inter-observer agreement for the assessments was calculated using the Intraclass Correlation Coefficient (ICC). Looking into specific characteristics of both the injury and the damaged subject, the assessors were more consistent in quantifying the damage in male subjects (ICC 0.68) and in subjects aged over 50 years (ICC 0.81) as well as in assessing extensive damages (ICC 0.61) than those of mild severity (ICC 0.41). The assessment of impairments located in the facial area resulted in a high level of concordance (ICC 0.73), while damages located the head and neck regions presented the lowest concordance (ICC 0.35). The evaluators were more consistent in assessing the outcomes of burns (ICC 0.70). Regardless the various reasons underlying the different degree of concordance, these results and the high degree of the overall concordance (ICC 0.63) point out the skillfulness of medicolegal professionals to formulate a complex judgment as more objectively as possible. Finally, an operative proposal was outlined to guide medico-legal professionals or interns in evaluating the aesthetic damage as more objectively as possible.

Whole-body diffusion-weighted MR and FDG-PET/CT in Hodgkin Lymphoma: Predictive role before treatment and early assessment after two courses of ABVD

PURPOSE

To evaluate whether imaging features of pathologic lymph nodes on whole-body diffusion-weighted MR have a predictive role before treatment and may assess the response after two courses of chemotherapy in comparison to FDG-PET/CT in Hodgkin Lymphoma.

MATERIALS AND METHODS

We reviewed the whole-body MR and FDG-PET/CT performed on 41 patients with Hodgkin Lymphoma before and after two Doxorubicin-Bleomycin-Vinblastine-Dacarbazine (ABVD). Responder and non-responder lesions were identified on interim-FDG-PET/CT performed after two ABVD. We used Multivariate Generalized Estimating Equations model to assess statistical association between being-responder and baseline-Maximum Standard Uptake Value (SUV_max), baseline and interim-Apparent Diffusion Coefficient (ADC) and size, ADC and size changes during chemotherapy, site of disease, bulky, and stage.

RESULTS

10/41 (24%) patients were positive on interim-FDG-PET/CT. The interim-FDG-PET/CT positivity was associated with worse cumulative survival rate at 24 months in comparison to interim-FDG-PET/CT negativity (P < .05); 3/10 patients with positive interim-FDG-PET/CT and 1/31 with negative interim-FDG-PET/CT experienced disease progression. Baseline-SUV_max was 11.18 ± 5.58 (3.1-28.0) and baseline-ADC was 0.70 ± 0.14 × 10^-3 mm²/s (0.39-0.98). There was a significant difference between responder and non-responder lesions based on interim-ADC (1.83 ± 0.34 × 10^-3 mm²/s vs. 1.01 ± 0.27 × 10^-3 mm²/s;p <.001), interim-size (3.1 cm² vs. 9.4 cm²;p = .009), and bulky (8.2% vs. 66.7%;p = .002). There was no significant difference between responder and non-responder lesions based on baseline-SUV_max (p = .713), baseline-ADC (p = .253), ADC changes (p = .058), size changes (p = .085), site (p = .209), stage (p = .290), baseline-size (p = .064).

CONCLUSIONS

Interim-ADC is helpful for identifying non-responder lesions, while size changes are not useful. Baseline-SUV_max and ADC have no predictive role. Bulky is the most useful imaging parameter to predict suboptimal response to chemotherapy.

Larotrectinib for paediatric solid tumours harbouring NTRK gene fusions: phase 1 results from a multicentre, open-label, phase 1/2 study

BACKGROUND

Gene fusions involving NTRK1, NTRK2, or NTRK3 (TRK fusions) are found in a broad range of paediatric and adult malignancies. Larotrectinib, a highly selective small-molecule inhibitor of the TRK kinases, had shown activity in preclinical models and in adults with tumours harbouring TRK fusions. This study aimed to assess the safety of larotrectinib in paediatric patients.

METHODS

This multicentre, open-label, phase 1/2 study was done at eight sites in the USA and enrolled infants, children, and adolescents aged 1 month to 21 years with locally advanced or metastatic solid tumours or CNS tumours that had relapsed, progressed, or were non-responsive to available therapies regardless of TRK fusion status; had a Karnofsky (≥16 years of age) or Lansky (<16 years of age) performance status score of 50 or more, adequate organ function, and full recovery from the acute toxic effects of all previous anticancer therapy. Following a protocol amendment on Sept 12, 2016, patients with locally advanced infantile fibrosarcoma who would require disfiguring surgery to achieve a complete surgical resection were also eligible. Patients were enrolled to three dose cohorts according to a rolling six design. Larotrectinib was administered orally (capsule or liquid formulation), twice daily, on a continuous 28-day schedule, in increasing doses adjusted for age and bodyweight. The primary endpoint of the phase 1 dose escalation component was the safety of larotrectinib, including dose-limiting toxicity. All patients who received at least one dose of larotrectinib were included in the safety analyses. Reported here are results of the phase 1 dose escalation cohort. Phase 1 follow-up and phase 2 are ongoing. This trial is registered with ClinicalTrials.gov, number NCT02637687.

FINDINGS

Between Dec 21, 2015, and April 13, 2017, 24 patients (n=17 with tumours harbouring TRK fusions, n=7 without a documented TRK fusion) with a median age of 4·5 years (IQR 1·3-13·3) were enrolled to three dose cohorts: cohorts 1 and 2 were assigned doses on the basis of both age and bodyweight predicted by use of SimCyp modelling to achieve an area under the curve equivalent to the adult doses of 100 mg twice daily (cohort 1) and 150 mg twice daily (cohort 2); and cohort 3 was assigned to receive a dose of 100 mg/m² twice daily (maximum 100 mg per dose), regardless of age, equating to a maximum of 173% of the recommended adult phase 2 dose. Among enrolled patients harbouring TRK fusion-positive cancers, eight (47%) had infantile fibrosarcoma, seven (41%) had other soft tissue sarcomas, and two (12%) had papillary thyroid cancer. Adverse events were predominantly grade 1 or 2 (occurring in 21 [88%] of 24 patients); the most common larotrectinib-related adverse events of all grades were increased alanine and aspartate aminotransferase (ten [42%] of 24 each), leucopenia (five [21%] of 24), decreased neutrophil count (five [21%] of 24), and vomiting (five [21%] of 24). Grade 3 alanine aminotransferase elevation was the only dose-limiting toxicity and occurred in one patient without a TRK fusion and with progressive disease. No grade 4 or 5 treatment-related adverse events were observed. Two larotrectinib-related serious adverse events were observed: grade 3 nausea and grade 3 ejection fraction decrease during the 28-day follow-up after discontinuing larotrectinib and while on anthracyclines. The maximum tolerated dose was not reached, and 100 mg/m² (maximum of 100 mg per dose) was established as the recommended phase 2 dose. 14 (93%) of 15 patients with TRK fusion-positive cancers achieved an objective response as per Response Evaluation Criteria In Solid Tumors version 1.1; the remaining patient had tumour regression that did not meet the criteria for objective response. None of the seven patients with TRK fusion-negative cancers had an objective response.

INTERPRETATION

The TRK inhibitor larotrectinib was well tolerated in paediatric patients and showed encouraging antitumour activity in all patients with TRK fusion-positive tumours. The recommended phase 2 dose was defined as 100mg/m² (maximum 100 mg per dose) for infants, children, and adolescents, regardless of age.

FUNDING

Loxo Oncology Inc.