419 Background: The 21 st Century Cures Act requires electronic health data to be available to patients. However, such data are useful to patients only if they access it. For example, imaging data can indicate the effectiveness of treatment and progression of disease and engagement with this information empowers patients to become more active in their care. While prior studies have explored the prevalence and timing of patient access to clinical notes, the timing of patient access to other data types remains unknown. We analyzed how rapidly oncology patients access the results of their imaging studies. Methods: Memorial Sloan Kettering Cancer Center (MSK) is a cancer center in New York that provides 700,000 imaging studies annually. At the time of this analysis, MSK had an internally developed patient portal, MyMSK, which notified patients via email about the presence of new data in the portal. The default timing for notifications was daily at 8 a.m. (patients could change notifications to be real-time, but very few did). We selected an arbitrary 7-day period (4/1/2023-4/7/2023) for analysis. For that week, for all imaging studies performed at MSK, we measured the time from when the report was available in the database (and thus available to the patient in MyMSK) to the time the report was read by either a patient or a proxy. The day the imaging study was performed was defined as “Day 0”. We determined (i) the proportion of imaging study reports that were read by 8 a.m. on Day 1, i.e., before any notification was sent to the patient, (ii) the proportion of reports that were read on Day 1 between 8 a.m. and 5 p.m., (iii) the proportion of reports that were read after 5 p.m. on Day 1, and (iv) the proportion not yet read by 8/23/2023 (when the data were collected). Results: In this one-week period, a total of 7,110 patients had 10,298 imaging studies. The average age of the patients was 61.4 years, 61.3% were female, 85.5% were non-Hispanic, 75.8% were White, and 95.1% reported English as their preferred language. Of the 10,298 imaging reports, 3203 (31.1%) were read before 8 a.m. on Day 1, 2090 (20.3%) were read between 8 a.m. and 5 p.m. on Day 1, 2389 (23.2%) were read after 5 p.m. on Day 1, and 2616 (25.4%) were not read as of 8/23/2023. Conclusions: This analysis indicates that a substantial proportion of cancer patients seek the results of imaging studies very soon after the tests are performed. Almost a third of the time, the patient read the report before any notification arrived. In oncology, it is easy to imagine patients frequently refreshing their portal to see if results have been posted. It is vital for provider organizations to understand the eagerness with which patients await results. Organizations may also want to develop methods to answer questions patients may have about their results prior to speaking with providers; this may be a key opportunity to leverage emerging artificial intelligence techniques.