Synovial Sarcoma in Children, Adolescents, and Young Adults: A Report From the Children's Oncology Group ARST0332 Study

Abstract

Purpose: Synovial sarcoma (SS) is the second most common malignant soft tissue tumor in children. ARST0332 evaluated a risk-based treatment strategy for young patients with soft tissue sarcoma designed to limit therapy for low-risk (LR) disease and to test neoadjuvant chemoradiotherapy for unresected higher-risk disease.

Methods: Newly diagnosed patients with SS age < 30 years were assigned to four treatment arms based on disease features: A (surgery only), B (55.8 Gy radiotherapy [RT]), C (ifosfamide and doxorubicin [ID] chemotherapy plus 55.8 Gy RT), and D (neoadjuvant ID and 45 Gy RT, then surgery and RT boost based on margins followed by adjuvant ID). Patients treated in Arms A and B were considered LR, arms C and D without metastases as intermediate-risk (IR), and those with metastases as high-risk (HR).

Results: Of the 146 patients with SS enrolled, 138 were eligible and evaluable: LR (46), IR (71), and HR (21). Tumors were 80% extremity, 70% > 5 cm, 70% high-grade, 62% invasive, 95% deep, and 15% metastatic. Treatment was on arm A (29.7%), B (3.6%), C (16.7%), and D (50%). There were no toxic deaths and four unexpected grade 4 adverse events. By risk group, at a median follow-up of 6.8 years, estimated 5-year event-free survival was LR 82%, IR 70%, and HR 8%, and overall survival was LR 98%, IR 89%, and HR 13%. After accounting for the features that defined risk category, none of the other patient or disease characteristics (age, sex, tumor site, tumor invasiveness, and depth) improved the risk stratification model.

Conclusion: The risk-based treatment strategy used in ARST0332 produced favorable outcomes in patients with nonmetastatic SS relative to historical controls despite using RT less frequently and at lower doses. The outcome for metastatic SS remains unsatisfactory and new therapies are urgently needed.

Trial registration: ClinicalTrials.gov NCT00346164.

Conflict of interest statement

R. Lor RandallHonoraria: Biomet, Daiichi Sankyo, Onkos Surgical, OncliveTravel, Accommodations, Expenses: Biomet, Daiichi Sankyo/Lilly James AndersonEmployment: MerckStock and Other Ownership Interests: Merck Sharp & DohmeTravel, Accommodations, Expenses: Merck Sharp & Dohme Andrew OstrengaHonoraria: Amgen Alberto PappoHonoraria: Bayer, RocheConsulting or Advisory Role: Merck, Loxo/Bayer, EUSA Pharma, Debbio Sheri L. SpuntResearch Funding: LOXO Oncology/Bayer AG/MedPace Inc, Bayer Healthcare Pharmaceuticals, Inc - USNo other potential conflicts of interest were reported.

Figures

FIG 1.

ARST0332 risk-based treatment assignment schema. HR, high-risk; IR, intermediate-risk; LR, low-risk; RT, radiotherapy.

FIG 2.

CONSORT diagram. HG, high-grade; HR, high-risk; IR, intermediate-risk; LG, low-grade; LR, low-risk; RT, radiotherapy; SS, synovial sarcoma.

FIG 3.

EFS and OS by risk group. Kaplan-Meier curves representing (A) EFS and (B) OS for patients in the LR, IR, and HR groups. EFS, event-free survival; HR, high-risk; IR, intermediate-risk; LR, low-risk; OS, overall survival.

FIG 4.

EFS and OS by treatment arm. Kaplan-Meier curves representing (A) EFS and (B) OS for patients treated on arm A (surgery alone), arm B (RT), arm C (adjuvant chemoradiotherapy), and arm D (neoadjuvant chemoradiotherapy). EFS, event-free survival; OS, overall survival; RT, radiotherapy.