Gauging sustainable cancer (CA) prevention in Lynch syndrome (LS): Attitudes toward dietary interventions.

e15655 Background: LS is among the most common hereditary CA syndromes, characterized by autosomal dominant inheritance of mismatch repair deficiency with increased lifetime risk of multiple CA types. While intensive screening can lower risk of LS-associated CAs, additional preventive measures could be broadly beneficial for motivated patients (pts). Our recent study (Singhal S et al, JCO Precision Oncology 2024), however, found that pts with LS reported only modest uptake of daily ASA/NSAIDs, a proven prevention option. In this study, we examine perceptions of dietary interventions as an alternative CA prevention option in a multi-national cohort of pts w/LS. Methods: PREVENTLynch study recruited pts w/LS to complete an online survey about screening behaviors and perceptions of novel prevention options. Pts were recruited through the Fox Chase Cancer Center (FCCC) Risk Assessment Program Registry and invitations posted via LS advocacy websites. In addition to reporting demographic factors, personal history, and screening behaviors, pts rated five dietary interventions: resistant starch supplements (RS), vitamin supplements (VS), online nutritional feedback (ONF), intermittent fasting (IF), and low inflammatory index diet (LID) (scale 0-10, low-to-high). Pts evaluated each intervention for perceived inconvenience, concern for side effects, reassurance to reduce CA risk, and study participation interest. Perception scores were colonoscopy (CO) benchmarked. Differences were tested by rank sum testing (Wilcoxon). The study was IRB approved (FCCC #20-8014). Results: A total of 296 responses were received. Participants were diverse by age [8% < 35 yr, 74% 35-65 yr, 18% > 65 yr] and location (39 states; 15% non-US based) but predominantly female (84%) and non-Hispanic white (92%). VS (1.77), ONF (1.94) and RS (2.00) were significantly more convenient than CO (3.40) (p < 0.001). Perceived side effects of ONF (1.81) (p < 0.001) were lowest compared to CO (2.46), especially in US participants (1.73) vs non-US (2.31) (p < 0.05). In contradistinction, CO reassurance (8.25) was significantly higher than all interventions (VS 5.04, RS 4.85, NF 5.72, OF 4.95, LI 5.04, all p < 0.001). Notably, pts with neoplasia history had the lowest reassurance from IF (4.73, p < 0.001), while non-US participants rated VS (3.49 vs 5.28), IF (4.08 vs 5.10) and LI (4.4 vs 5.24) (all p < 0.001) significantly less favorably. Study participation interest was highest for RS (7.31) and NF (7.06) and lowest for IF (6.31). Conclusions: Dietary interventions show promise as low-risk adjuncts to CO surveillance with favorable perceived acceptability and side effects among LS pts. Our findings highlight the importance of considering pt preferences when developing and testing risk-reducing interventions to maximize real-world uptake and downstream effectiveness.