(P 318) SYNOVIAL SARCOMA REGISTRY AND BIOSPECIMEN REPOSITORY: DESCRIBING THE COHORT AND SURVIVAL OUTCOMES TO DATE

Objective: The Synovial Sarcoma Registry and Biospecimen Repository (SSRBR) aims to advance clinical and translational research in synovial sarcoma, with the ultimate goal of impacting patient care and survival. The SSRBR is established for all patients treated with synovial sarcoma in the United States to collect clinical information and serve as a biospecimen repository. With the SSRBR, we seek to characterize the patient population, create a central database of clinical information, imaging results, and genomic data, and generate a biospecimen repository, all of which can be integrated to expand research endeavors. Herein, we describe the SSRBR design and preliminary data.

Methods: The SSRBR is established at the Children’s Hospital of Philadelphia (CHOP). Informed consent is completed in person or remotely. Remote consent initially required a phone conversation with study staff and recently transitioned to a self-guided online consent. Patients are recruited through CHOP and the social media platforms of support groups. At the time of enrollment, patients complete an intake survey, and medical records are requested from all outside institutions at which registrants receive care. Data collection is ongoing, as records are reviewed at enrollment and every subsequent 6-12 months for up to 10 years.

To establish a biospecimen repository, serial blood samples are collected from patients receiving care at CHOP. Additionally, residual tumor tissue from any surgical intervention is requested for all patients. Tissue will undergo testing in a CLIA-approved lab and clinically relevant results will be returned to both patients and their physicians. Additionally, tissue may also be stored for future research and, if viable, transplanted into mice to generate patient-derived xenograft (PDX) models. Coordination is ongoing to facilitate receipt of specimens from patients receiving care at outside institutions.

Results: The SSRBR was established June 2023 and the data cut-off for this report was April 1, 2024. In the initial ten months, 46 patients consented to enrollment, and an additional 3 deceased patients were enrolled. Of these 49 patients, 48 (98.0%) were eligible, with one ineligible due to a lack of synovial sarcoma diagnosis. Medical records were obtained for 46 (93.8%) of the eligible patients. Forty patients have been in the registry for six or more months. Six patients were deceased by the time of the first follow-up. Twenty living patients have been sent their first follow-up survey, which has been completed by 15 (75% response rate). At this time, tissue from two patients has been transplanted into mice with the intent of generating PDX models.

The patient population has received medical care across 25 states and the District of Columbia. Patient demographics are summarized in Table 1. Briefly, the registry is composed of 29 (63%) female and 17 (37%) male patients. Age at initial diagnosis ranged between 0-9 years old for 2 (4.3%), 10-17 years old for 11 (23.9%), and 18 or older for 33 (71.7%) patients. Notably, 6 (13%) had metastatic disease at the time of diagnosis. The overall 5-year survival rate was 81.5% for patients with non-metastatic disease and 50% for patients with metastatic disease (Figure 1). The median survival for patients with non-metastatic disease has not yet been reached. Within the SSRBR, median follow-up time was 2.58 years in patients with non-metastatic disease and 3.24 years in patients with metastatic disease.

Conclusion: The SSRBR has been established with the successful enrollment of an initial patient population. To enhance engagement, a quarterly newsletter is sent to study participants outlining study progress and collaborations. Additionally, CHOP hosts a monthly synovial sarcoma tumor board open to medical practitioners worldwide during which the SSRBR is publicized. Dedicated staff and resources have been necessary for requesting records from multiple outside institutions. One challenge is institutions having varied legal requirements for releasing records of deceased patients which may impact ongoing patient follow-up. Intentions to recruit internationally have been impacted by legal limitations. Coordination is ongoing to optimize sample collection for the biospecimen registry, both for patients cared for at CHOP and at outside institutions.

Currently, assessment of outcomes from the registry is limited due to the small sample size. Ongoing patient enrollment will be necessary to expand analyses to include assessment of therapies utilized, survival in population subsets, and correlation with molecular alterations. Our data may be biased towards people who are living with relapsed disease, as these individuals may be more motivated to join the SSRBR. However, this may also provide an opportunity to study high-risk disease features.