Abstract 1504P
Background
Synovial Sarcoma (SS) is a rare and biologically aggressive - generally considered high-grade - soft tissue sarcoma. With an annual incidence of 1.4 cases per million in the UK, the prognosis for SS patients is poor. There is no established standard of care for metastatic SS (mSS) beyond 1st line of therapy (LoT). This real-world study aimed to be the first to contextualise the therapeutic landscape and survival outcomes of mSS patients in England using the Cancer Analysis System, a population-level cancer database.
Methods
This study included systemic anti-cancer therapy (SACT) treated SS patients between 2011 and 2021. Metastatic SS patients were categorised as Stage IV or Stage I-III/unknown who progressed to mSS; progression was proxied by initiating a 2nd LoT, defined using a LoT algorithm. Treatment patterns were described, and Overall Survival (OS) and Time to Next Treatment or Death (TTNTD) were assessed through Kaplan-Meier methods.
Results
Of the 238 eligible SS patients identified during the study period, 133 (56%) were metastatic, with a median follow-up (IQR) of 11.9 (6.6-23.3) months. Median age at mSS diagnosis was 39.0 (5th-95th percentile: 19.0-69.4) years. Cytotoxic agents were the most common treatments across all metastatic LoTs. Doxorubicin-containing regimens dominated the 1st LoT. SACTs at 2nd LoT (N=87) were heterogeneous: trabectedin, docetaxel + gemcitabine, and ifosfamide were administered to 31%, 16% and 14% of patients, respectively. Pazopanib use was infrequent. Median OS and TTNTD were, respectively, 12.2 (6.1-23.6) and 6.0 (2.8-10.5) months from 1st LoT; 9.6 (4.1-15.6) and 5.3 (2.4-10.4) months from 2nd LoT; 5.1 (3.6-12.6) and 4.3 (2.5-7.5) months from 3rd LoT; 4.3 (2.7-7.5) and 3.7 (2.5-5.0) months from 4th LoT.
Conclusions
This study provides a key benchmark for understanding current mSS management trends in England. Over half of the eligible SS patients had mSS and an average of 13 mSS patients per year received SACT from 2011-2021. The main treatment was cytotoxic agents. Beyond the 1st metastatic LoT, there was no clear established therapy. OS and TTNTD estimates suggest diminishing benefit of treatment beyond 2nd LoT, and a need for improved therapies in this population.
Clinical trial identification
Editorial acknowledgement
Legal entity responsible for the study
Adaptimmune.
Funding
Adaptimmune.
Disclosure
S.L. McGuigan: Other, Institutional, Advisory Role: Adaptimmune. C. Lunt: Other, Institutional, Advisory Role: Adaptimmune. E. Van Winkle: Other, Institutional, Advisory Role: Adaptimmune. S. Biswas: Other, Institutional, Project Lead: Adaptimmune. All other authors have declared no conflicts of interest.