279 Background: In the last years, the introduction of immune checkpoint inhibitors (ICI) in clinical practice translated into major changes in oncology workload. We conducted a study aimed to estimate the shift in workload generated, within 1 year of first consultation, by any new metastatic cancer patient receiving ICI at the Oncology Department of the Academic Hospital of Udine, Italy. Methods: We collected from our electronic accountability system data all new cases of metastatic cancer between 01.01.2017 and 31.12.2018, leading to at least a second clinical episode (treatment sessions, unplanned presentations, hospitalizations, re-evaluations, follow-up, and inpatient oncology advices) during the following year. Patients (pts) were divided into those receiving ICI (anti-CTLA4/PD1/PDL1) versus pts receiving other treatments. Mean number per patient and standard deviation were calculated for clinical episodes, and the mean numbers in each group were compared using Student’s t-test (significance p<0.05). Follow-up continued until 31.12.2019. Results: 969 pts were included: 115 were treated with ICI, 854 received other treatments. In the first group a greater number of treatment sessions, re-evaluations and unplanned presentations was generated, with a statistically significant increased workload. On the other hand, pts receiving other treatments generated a greater workload in terms of follow-up. In detail, data are reported in Table. Conclusions: ICI have transformed the oncology landscape, leading to longer lasting treatment period with emerging toxicities. Estimating the workload generated by ICI is crucial for the implementation of more sustainable systems and for planning clinical activities. Mean number of clinical episodes in the first year of treatment with ICI for metastatic disease. Mean number per patient is represented by mean value and standard deviation (SD). Total number of clinical episodes is shown (N=). Data are reported for ICI versus other treatments group. [Table: see text]