Purpose: The aims of this study were to compare the application of three geriatric medication screening tools to the Beers Criteria alone for potentially inappropriate medication quantification and to determine feasibility of a pharmacist-led polypharmacy assessment in a geriatric oncology clinic.Methods: Adult patients with cancer aged 65 and older underwent a comprehensive geriatric assessment. A polypharmacy assessment was completed by a pharmacist and included a review of all drug therapies. Potentially inappropriate medications were screened using the Beers Criteria, Screening Tool to Alert doctors to Right Treatment/Screening Tool of Older Persons' Prescriptions, and the Medication Appropriateness Index. Deprescribing occurred after discussion with the pharmacist, geriatric oncologist, patient, and caregiver.Results: Data were collected for 26 patients. The mean number of medications was 12. The Beers Criteria alone identified 38 potentially inappropriate medications compared to 119 potentially inappropriate medications with the three-tool assessment; a mean of 5 potentially inappropriate medications were identified per patient. After the application of the three-tool assessment, 73% of potentially inappropriate medications identified were deprescribed, resulting in a mean of 3 medications deprescribed per patient. Approximately two thirds of patients reported a reduction in symptoms after the deprescribing intervention. Healthcare expenditures of $4282.27 per patient were potentially avoided as a result of deprescribing.Conclusions: Our three-tool assessment identified three times more potentially inappropriate medications than the Beers Criteria alone. Pharmacist-led deprescribing interventions are feasible and may lead to improved patient outcomes and cost savings. This three-tool assessment process should be incorporated into interdisciplinary assessments of older patients with cancer and validated in future studies.