Background: In clinical trials, the systematic collection of patient (pt) reported outcomes has been shown to improve quality of life & overall survival. To develop predictive care models for symptom management, we explored the frequency & distribution of SAEs reported by pts who reported electronic patient reported outcomes (ePRO) prior to outpatient visits to the Gastrointestinal Cancer Center (GCC) at Dana Farber Cancer Institute (DFCI). Methods: ePRO is a modified NCI Patient Reported Outcomes – Common Terminology Criteria for Adverse Events instrument distributed weekly to GCC pts with a medical/surgical/radiation oncology encounter. Responses are available to the care team in the electronic health record. ePRO consists of presence/frequency/severity/interference of 15 core SAEs (fatigue, insomnia, general pain, decreased appetite, nausea, vomiting, constipation, diarrhea, shortness of breath, numbness and tingling, rash, concentration, fever, anxiety, sadness). Responses are scored 0 to 3 (with 2 and 3 indicating moderate and severe SAEs, respectively). We examined the frequency & distribution of grade 2 and 3 SAEs in ePRO responders by age, gender, race/ethnicity. All pts had gastrointestinal cancer and an outpatient visit for treatment, symptom management, follow-up care. Results: From 9/1/2018 to 8/31/2020, 1912 unique pts responded (response rate 23%). Most respondents were age 50-69 years (58% compared to 15% age <50, 27% age ≥70; range 18-95), male (53%), white (75%). Grade 3 SAE frequencies were pain (12%), fatigue (11%), anxiety/constipation/insomnia/decreased appetite (5%), sadness/numbness and tingling/diarrhea (3%), concentration/shortness of breath (2%), nausea/rash (1%), fever/vomiting (0%). Across pts, fatigue, general pain, insomnia, anxiety were the most common grade 2 and 3 SAEs. Shortness of breath, vomiting, rash, fever were least common (Table). Conclusions: In GCC pts responding to ePRO, the most frequent SAEs were pain, fatigue, insomnia, anxiety. Shortness of breath, nausea, vomiting, diarrhea were less often severe. Pts <50 were more likely to report severe anxiety but there were no other major differences based on age, sex, race/ethnicity. Ongoing efforts will increase pt/provider engagement and develop predictive models & symptom management interventions from ePRO responses.