Background: A novel Oncology-Acute Care for Elders (OACE) unit that uses an interdisciplinary team to enhance recognition and management of geriatric syndromes in hospitalized older adult cancer patients has been established at Barnes-Jewish Hospital (St. Louis, Missouri). The OACE team includes a clinical pharmacist whose primary role is to improve the appropriateness of prescribing. Objective: Using polypharmacy as the prototypical geriatric syndrome addressed by the OACE team, the objective of this study was to document the processes of communication of an interdisciplinary team and the impact on polypharmacy when the treating physician did not participate in the daily interdisciplinary team rounds. Methods: This was a prospective, observational study of older cancer patients admitted to the OACE unit. We tracked processes and outcomes of interdisciplinary communication regarding medications by prospectively recording OACE team recommendations and evaluating the frequency of implementation of these recommendations through a chart review. Treating physicians, who did not attend team rounds, received these recommendations on a communication form placed in the patient's chart. Results: Forty-seven patients were included in the study. The mean (SD) age was 73.5 (7.5) years. Twenty-one percent (10/47) of patients were prescribed ≥1 Beers medication as part of their home-care regimen before admission to the OACE unit. The OACE team made 51 medication recommendations, and 42 of those recommendations (82%) were implemented. Twenty-five patients (53%) had an alteration in their medication regimen; 13 (28%) had a potentially inappropriate medication discontinued. A medication error was corrected in ~1 of every 8 patients (6/47 [13%]). Conclusions: We found that polypharmacy was common in older cancer patients and increased during hospitali-zation. We also found that most OACE team recommendations communicated to physicians were implemented even though the primary physicians were not members of the OACE team. Future randomized trials are needed to assess the impact of the OACE team model of care on adverse events, survival, and cost in hospitalized older adult cancer patients. © 2009 Excerpta Medica Inc. All rights reserved.