PROgress Tracker Breast Cancer Registry: Reporting worry of illness from a longitudinal peer-led, national patient-reported outcomes (PRO) registry.

11112 Background: PROgress Tracker Breast Cancer Registry is a national, ethics approved non-interventional patient-reported outcome measure (PROMs) registry, using a peer-to-peer model directed by patient advocacy group Breast Cancer Canada. Here, initial results report breast cancer survivors nature of cancer illness worry and intensity based on age, stage and molecular subtype at diagnosis. Methods: PROgress Tracker was launched in 2023, with enrollment over 10 years of Canadians with Stage 0-IV breast cancer. Participants self-refer and complete a series of validated PROMs (demographic, socioeconomic, clinical, global wellbeing) via a digital platform, capturing current status on a quarterly basis for up to 10 years. Real-world analysis assisted by AI ( January 2026; Claude [Opus 4.5], manufacturer: Anthropic; data extraction, statistical analysis with means, percentages, patient-level aggregation, stratification by clinical variables, longitudinal pattern analysis and visualization; all outputs validated against source data ) of FACT-B PROM data capture and analysis methodology was used. Results: To date, 823 participants have enrolled with 186 participating for ≥2 years. From participation start, longitudinal worry is reported using 3 factors from FACT-B PROM; hereditary risk of family members (HR), if stress impacts illness (SI), and if participant’s condition will worsen (CW). Highest degree of reported worry scores was in HR 40.4% (n = 74), SI 31.7% (n = 59) and CW at 17.4% (n = 32). Worry intensity varied by age, stage and molecular subtype. Participants diagnosed < 50 years reported higher levels in all 3 factors (HR 51% mean 2.53; SI 46.9% mean 2.24; CW 24.5% mean 1.78) to those at > 50 years (HR 37.1% mean 1.92; SI 25.9% mean 1.63; CW 14.3% mean 1.32). Stage IV participants show 66.7% high worry (CW and HR) compared to stage I at 8.5% (CW). Molecular subpopulations show higher worry in HR- / HER2- (TNBC) n = 34 (HR 48.5% mean 2.24; SI 38.2% mean 2.00; CW 17.6% mean 1.59) compared to HR+ / HER2- n = 81 (HR 37.5% mean 2.04; SI 35.4% mean 1.90; CW 17.3% mean 1.41) and HR+ / HER2+ n = 13 (HR 30.8% mean 2.08; SI 23.1% mean 1.77; CW 7.7% mean 1.38). Non-linear trajectory over time shows 24% (n = 183) experienced high worry at registry entry, declining at 12 months to 15.8% with a secondary peak at 18 months in 21.7% of participants. Conclusions: Patient-reported outcomes show the burden of worry by breast cancer survivors for hereditary risk to family and individuals’ illness. These findings offer directional insights for psychosocial screening, care resources and tailored education throughout survivorship.