Estimating survival in advanced cancer: A prospective single-center study on the accuracy of oncologists’ prognostic accuracy (Pre-Sur).

11133 Background: The ability to estimate survival is a cornerstone of care for patients (pts) with advanced cancer, influencing therapeutic strategies, access to clinical trials, and timing of palliative care referral. Existing evidence on clinical prediction of survival (CPS) largely derives from end-of-life pts. The Pre-Sur study addresses this gap by evaluating oncologists’ prognostic accuracy in pts with metastatic solid tumors starting first-line therapy and investigating discordance-related factors. Methods: Pre-Sur is a prospective, observational, monocentric study enrolling pts with advanced tumors prior to first-line therapy (hormonal therapy was excluded). During the baseline consultation, clinicians provided an estimated survival timeframe using categorical intervals (0-4 to >36 months). The primary endpoint was concordance between CPS and overall survival (OS). Survival estimates and outcomes were analyzed descriptively and through cross-tabulation. Secondary analyses explored factors potentially influencing accuracy, including ECOG-PS, age, comorbidities, and clinician characteristics, using Chi-square tests and multivariable models. Results: From October 2022 to December 2025, 183 pts were enrolled; 135 completed the required follow-up. 58% of pts were male and 49% were ≥75 years. Gastrointestinal (45%) and thoracic (35%) cancers were the most prevalent. Median CPS (mCPS) was 18.0 months (95%CI: 15.9–20.0), median OS (mOS) of 8.0 months (95%CI: 5.9–10.0). Prognostic estimates were accurate in 17% of cases, optimistic in two-thirds, and underestimated in less than one-quarter. No significant associations emerged for sex, tumor site, PS or target therapy use. mCPS were often more consistent with the mOS reported in randomized clinical trials (RCT); the observed real-world OS were inferior to that expected from RCT (Table 1). Conclusions: This study highlights the difficulty of predicting OS in pts with metastatic solid tumors. CPS may be influenced by expectations derived from RCT outcomes, which may not fully capture the complexity of real-world pts. Prognostic evaluation in clinical practice should integrate features such as age, PS, comorbidities, and disease burden, to improve prognostic accuracy and support informed decision-making. Overall survival and clinical prediction of survival by disease sites. Site Patients, n (%) mOS, months (CI 95%) mCPS, months (CI 95%) mOS trend in registrative RCTs, months Lung 44 (32.2) 7 (2-12) 12 (11-13) 12-26 Colorectal 24 (17.8) 9 (5-13) 18 (13-23) 25-30 Pancreas 15 (11.1) 8 (2-14) 24 (21-27) 11 Gastric 11 (8.1) 5 (2-8) 12 (7-17) 14 Head and neck 6 (4.4) 6 (0-13) 30 (NA-NA) 15 Kidney 6 (4.4) 6 (4-8) 18 (5-30) 45 Biliary ducts 5 (3.7) 2 (1-3) 18 (13-23) 12 Pleural 4 (3.0) 2 (NA-NA) 8 (NA-NA) 12 Skin 4 (3.0) 22 (NA-NA) 12 (NA-NA) 33 Bladder 3 (2.2) 11 (0-27) 18 (8-28) 21