Background: Timing of biomarker results is critical to informing the selection of appropriate precision medicine-based treatment options for patients. Prior studies have demonstrated that low rates of biomarker testing may be driven by poor documentation. Our clinical decision support (CDS) tool aims to provide community oncology clinicians with a clear picture of the ever-growing available treatments. Evaluation of CDS data revealed an excess of biomarker results documented as “unknown” thought to be related to results availability. Methods: During treatment selection in the CDS tool, providers answer various prompts related to the patient’s disease, staging, treatment intent, and biomarker results. Prompts are aligned with NCCN guidelines for the respective cancer type. Changes were implemented to ease providers’ documentation of biomarker results. For adjuvant (adjNSCLC) and metastatic NSCLC (mNSCLC), prompts were relocated to align with when biomarker results were likely to be available. For metastatic castrate resistant prostate cancer (mCRPC), some biomarkers are only needed after a patient has received prior docetaxel and hormone therapy, thus prompts were moved to that scenario. Re-prompting of biomarker status for subsequent therapy was also implemented if the initial response was “unknown.” We report changes in percentage of known biomarkers specifically in adjNSCLC, mNSCLC, and mCRPC. Descriptive statistics were used to describe the rates of known biomarkers, and a chi-square test was used to analyze differences from pre and post changes. Results: In this evaluation, 85,493 biomarkers were documented. In adjNSCLC and mNSCLC, biomarker prompt changes increased documentation of known biomarkers from 69% to 78% and 59% to 79% pre- to post-implementation. In adjNSCLC, ALK and PD-L1 recording increased by ≥10% (P<0.00001). For mNSCLC, documentation increased for all known biomarkers (P<0.00001), including ≥15% increases for 8 of 10 biomarkers. In mCRPC, known biomarker documentation improved from 34% pre-implementation to 61% post-implementation. BRCA1/2, MSI, MMR, TMB, and PSMA biomarker recording increased by ≥20% (P<0.00001) after prompt changes. Selected biomarkers are shown in the table. Conclusions: Adjusting prompts in a CDS tool to align with the availability of biomarkers in clinical practice increased the documentation of known biomarker results for adjNSCLC, mNSCLC, and mCRPC. Based on these findings, similar changes are being implemented for other cancer types in the CDS tool.