Background: There is limited information about the clinical utility of targeted NGS panel testing to inform decision-making for patients with advanced solid tumors. The Ontario-wide Cancer Targeted Nucleic Acid Evaluation (OCTANE) is an ongoing prospective study that enrolled over 4,500 solid tumor patients for NGS panel testing. We performed a retrospective survey of 21 medical oncologists enrolling OCTANE patients at a single academic institution to evaluate the impact of NGS testing on treatment decisions. Methods: Patients and treating oncologists were identified at the Princess Margaret Cancer Centre between 2016-2021. Tumor-only sequencing was performed using a custom hybridization capture panel of 555 cancer genes (Hi5) or a commercial 161-gene amplicon DNA/RNA panel (Oncomine Comprehensive v3). Oncologists were asked to review testing results for individual patients and complete a survey indicating whether NGS testing impacted treatment decisions. Mutations were defined as actionable based on clinical judgment and compared to classifications provided by OncoKB, an FDA-recognized precision medicine knowledgebase. The primary outcome of this study was rate of treatment change based on mutation results. Patient, test, and physician factors were evaluated for association with treatment changes using univariate analyses and a mixed effects model. Results: Two cohorts were surveyed, the first between 2017-2019 and the second in 2021. Of the 582 surveys sent, 394 (67.7%) were completed. Each physician completed a median of 19 surveys (range, 9-48). We found that 188 (47.7%) patients had a mutation classified as actionable by the oncologist, of whom 134 (71.3%) had ≥1 OncoKB-defined actionable mutation(s). 62/394 (15.7%) patients were matched to a treatment, of whom 37 were enrolled in a clinical trial, 13 received an approved drug, 4 were prescribed off-label therapy and 8 avoided ineffective treatment. 127/188 (67.5%) patients with actionable mutations did not receive treatment due to lack of available therapy, stability on current regimen, clinical deterioration or patient decision. Rate of treatment change was highest for bowel (15/37, 40.5%), breast (14/52, 27.5%), biliary tract (6/22, 27.3%) and lung (4/17, 23.5%) cancers. Treatment decisions were not associated with patient age, gender, physician clinical experience, physician gender, testing experience, OncoKB mutation level or time from biopsy to sequencing. There was no difference in overall survival between patients with matched vs. no matched treatment (p = 0.55, median survival not reached). Conclusions: OCTANE testing led to a change in drug treatment in 15.7% of patients, supporting the clinical utility of NGS panel testing for patients with advanced solid tumors. Patient, test, and physician characteristics were not significantly associated with treatment change.