Treatment at relapse for synovial sarcoma of children and adolescents: A multi-institutional European retrospective analysis.

PURPOSE

Though the prognosis for pediatric patients with localised synovial sarcoma (SS) is generally good, the chances of being cured after relapse are limited. This study describes a retrospective multi-institutional series of relapsing SS patients treated at six selected European referral centers for pediatric sarcoma.

PATIENTS AND METHODS

The study included 41 patients <21 years with relapsing SS, treated between 2002 and 2022. The analysis included patient's characteristics at first diagnosis, first-line treatments, clinical findings at relapse, and second-line treatment modalities.

RESULTS

The first relapse occurred within 3-132 months (median 18 months) after first diagnosis and was local in 34%, metastatic in 54%, and both in 12%. Treatment at first relapse included surgery in 56% of cases, radiotherapy in 34%, and systemic therapy in 88%. In all, 36 patients received second-line medical treatment, that was chemotherapy in 32 cases (with 10 different regimens) and targeted therapy in four. No patient was included in an early-phase clinical trial as second-line therapy-line therapy. Overall response rate was 42%. Median event-free survival (EFS) was 12 months, postrelapse 5-year EFS was 15.8%. Median overall survival (OS) was 30 months, postrelapse 5-year OS was 22.2%. At the Cox's multivariable regression analysis, OS was significantly associated with time and type of relapse.

CONCLUSION

Pediatric patients with relapsed SS have a poor prognosis and generally receive an individualized approach, due to the lack of a uniform standardized approach. New comprehensive strategies are needed to improve the knowledge on the biologic landscape of SS and develop tailored prospective clinical trials.