Hello GLASS Data Team, I have separately contacted the Synapse Access and Compliance Team regarding data-access permissions and applicable Terms of Use. This request focuses specifically on the clinical definitions, endpoint validity, follow-up information, and cohort eligibility needed to assess scientific feasibility. I am conducting a documentation-only feasibility assessment for a research-stage glioma progression/recurrence prediction model. I have reviewed the GLASS Data Dictionary, including the clinical.cases, clinical.surgeries, analysis.tumor_pairs, analysis.blocklist, and analysis.rna_blocklist definitions. I have not accessed patient-level GLASS records or used GLASS data for model training. Before proceeding, I would appreciate clarification on the following questions. A. Confirmed recurrence or progression outcomes Does the current GLASS release provide an independently adjudicated clinical progression/recurrence endpoint, distinct from the clinical.surgeries.surgery_indication categories Progression and Relapse? If so, which table or field contains that endpoint, and what clinical criteria were used to establish it (for example, radiographic assessment, pathology, or clinical review)? B. Follow-up and censoring Does GLASS provide progression-free survival, time to first progression, date or interval of last progression-free assessment, or another way to determine that a patient remained progression-free during observation? How should patients without a documented subsequent progression-related surgery be handled? Are progression events that did not lead to surgery captured? C. Cohort eligibility and selection The Data Dictionary indicates that clinical.surgeries includes subjects with at least one sequenced recurrent tumor sample. Is there a GLASS table or approved cohort containing patients eligible at initial diagnosis regardless of whether they subsequently underwent recurrent-tumor surgery or sequencing? If not, would you recommend restricting analyses to the recurrent-sample-selected population rather than interpreting the results as diagnosis-time recurrence prediction? D. Baseline and temporal alignment For a longitudinal prediction study, which time origin is most defensible: first diagnosis, first surgery, or another defined clinical landmark? Are the dates or relative times needed to determine which clinical and molecular predictors were available at that baseline provided? E. Clinical quality-control exclusions The analysis.blocklist and analysis.rna_blocklist documentation describes clinical_exclusion values of allow, review, and block, including reasons such as interval1orless, interval2orless, differentlocation, and surgicalindication. Were these flags designed solely for molecular sample/pair eligibility, or can they support clinical recurrence endpoint adjudication? Does allow indicate only that a sample passed the applicable QC criteria, rather than an independently confirmed recurrence? F. Recommended research endpoint If independently adjudicated recurrence and progression-free follow-up are unavailable, would GLASS recommend any narrower, scientifically defensible endpoint based on longitudinal surgery information—for example, time to a subsequent progression/relapse-indicated surgery within the selected GLASS cohort? Are there relevant protocols, publications, data dictionaries, or contact persons you recommend consulting? My objective is to avoid misclassifying patients, introducing future-information leakage, or drawing conclusions beyond what the cohort design supports. I am requesting documentation and guidance only, not patient-level data or an exception to existing access restrictions. Thank you for your assistance. Best regards, Golbidi