Role of Metastatic Site Irradiation in Pediatric Patients With Metastatic Ewing Sarcoma

Stereotactic Body Radiation Therapy and Concurrent Targeted Therapy for Lung Metastases in Pediatric Sarcoma

Purpose

The purpose of this investigation was to evaluate the efficacy and safety of stereotactic body radiation therapy (SBRT) for pulmonary metastases from pediatric sarcomas.

Methods and Materials

This study was a single institutional retrospective chart review including patients younger than 21 years of age at diagnosis who had received SBRT for pulmonary metastasis from metastatic sarcoma. Our current electronic record system was queried for all eligible patients. Primary endpoint was tumor response as defined by Respone Evaluation Criteria in Solid Tumors 1.1 criteria. Secondarily, we analyzed factors that affected tumor response as well as toxicity of treatment. Median dose was 50 Gy ranging from 30 to 60 Gy in 5 fractions to the planning tumor volume.

Results

There were 7 patients, ranging in age from 6 to 21 years with a total of 14 pulmonary lesions treated with SBRT. Median and mean follow-up times for the 7 patients were 10.6 months and 15.9 months, respectively. The complete response rate was 50%, partial response 21%, stable disease 21%, and progressive disease 7%. Four of the 7 patients were treated with concurrent systemic therapy, 3 of which were targeted oral therapies. Additionally, we observed that patients who were on targeted therapy such as regorafenib or pazopanib seemed to have better local control compared with patients without targeted therapy.

Conclusions

With an overall response rate of 92%, SBRT provided a noninvasive effective palliative treatment option with few side effects in this small retrospective study of 7 patients. A larger prospective clinical trial is warranted to evaluate the role of SBRT in the treatment of unresectable metastatic pediatric sarcomas.

Outcomes of Pediatric Patients With Metastatic Ewing Sarcoma Treated With Interval Compression

BACKGROUND

Interval compression (IC), a regimen of alternating vincristine/doxorubicin/cyclophosphamide and ifosfamide/etoposide every 2 weeks, improves survival for localized Ewing sarcoma (ES), with uncertain effect on metastatic disease.

MATERIALS AND METHODS

We reviewed the charts of pediatric patients with metastatic ES treated with IC at our center between January 2013 and March 2020. We calculated event-free survival and overall survival (OS) and used log-rank tests for univariate comparisons.

RESULTS

We identified 34 patients 2.7 to 17.1 years of age (median: 11.6 y). Twenty-six patients (76%) had pulmonary metastases, and 14 (41%) had extrapulmonary metastases. All patients received local control therapy: surgery only (n=7, 21%), radiotherapy only (n=18, 53%), or both (n=9, 26%). The estimated 3-year OS and event-free survival were 62%±9% and 39%±9%, respectively. Patients with pulmonary-only and extrapulmonary metastasis had a 3-year OS of 88%±8% and 27%±13%, respectively ( P =0.0074). Age group (above vs. below 12 y), or primary tumor site did not affect survival, but local control therapy did (surgery only, 83%±15%; combined surgery and radiation, 30%±18%; radiation only, 15%±10%; P =0.048).

CONCLUSION

IC yielded similar outcomes for patients with metastatic ES to other reported regimens. We suggest including this approach to other blocks of therapy.

A New Proton Therapy Solution Provides Superior Cardiac Sparing Compared With Photon Therapy in Whole Lung Irradiation for Pediatric Tumor Patients

Objective

Whole lung irradiation (WLI) plays a crucial role in local control in pediatric patients with lung metastases and improves patient survival. The intention of this research was to explore the advantage of cardiac sparing between photons and protons during WLI. We also propose a new solution for cardiac sparing with proton techniques.

Methods

Eleven patients with pediatric tumors and pulmonary metastasis treated with 12 Gy WLI (all received volumetric-modulated arc therapy (VMAT)) in our institute between 2010 and 2019 were retrospectively selected. Each patient was replanned with intensity-modulated radiation therapy (IMRT), helical tomotherapy (HT), and two intensity-modulated proton radiotherapy (IMPT) plans (IMPT-1 and IMPT-2). IMPT-1 considered the whole lung as the planning target volume (PTV), utilizing the anteroposterior technique (0/180°). IMPT-2 was a new proton solution that we proposed in this research. This approach considered the unilateral lung as the PTV, and 3 ipsilateral fields were designed for each lung. Then, IMPT-2 was generated by summing two unilateral lung plans. The primary objective was to obtain adequate coverage (95% of the prescription dose to the PTV) while maximally sparing the dose to the heart. The PTV coverage, conformity index (CI), homogeneity index (HI), and dose–volume statistics of the heart and substructures were assessed by means of the averages of each comparison parameter.

Results

All treatment techniques achieved the target volume coverage required by clinical practice. HT yielded the best coverage and homogeneity for the target structure compared with other techniques. The CI from IMRT was excellent. For photon radiation therapy, the HT plan afforded superior dose sparing for the V₅, V₆, V₇, V₈, and D_mean of the heart and D_mean of the right ventricle (RV). IMRT displayed the most notable dose reductions in the V₉, V₁₀, V₁₁, and V₁₂ of the heart and D_mean of the right atrium (RA). The VMAT plan was the least effective on the heart and substructures. However, compared with photon radiation therapy, IMPT-1 did not show an advantage for heart protection. Interestingly, IMPT-2 provided significant superiority in cardiac sparing, including maximum dose sparing for the V₅, V₆, V₇, V₈, V₉ and D_mean of the heart and D_mean of the RA, RV, left atrium (LA) and left ventricle (LV) compared to all other techniques.

Conclusions

Considering the complex anatomical relation between target volumes and organs at risk (OARs), IMPT can provide a dose advantage for organs located outside of the target area rather than within or surrounding the area. It is hoped that advances in proton therapy (PT) plan design will lead to further improvements in radiotherapy approaches and provide the best treatment choice for individual patients.