Understanding the magnitude and risk-factors for symptom burden of cancer patients at the end-of-life is critical to guiding effective patient- and system-level interventions.We aimed to estimate the prevalence of severe patient-reported symptoms among cancer outpatients during the six months before death and to identify patient groups at a higher risk for reporting severe symptoms.This was a retrospective cohort study of cancer decedents at regional cancer centers from 2010-2016. Patient-reported Edmonton Symptom Assessment System (ESAS) scores from the last six months-of-life were linked to administrative databases. The proportion of patients reporting severe symptom scores (>7) for anxiety, depression, drowsiness, lack of appetite, nausea, pain, shortness of breath, tiredness, and overall wellbeing during the six months before death was described. Multivariable modified Poisson regression analyses were used to identify risk-factors for reporting severe symptom scores.22,650 of 39,084 cancer decedents had ≥1 symptom record in the last six months of life, resulting in 92,757 ESAS assessments. Severe scores were highest for tiredness (56%), lack of appetite (46%), and impaired wellbeing (45%). The proportion of patients reporting severe symptom scores was stable before progressively increasing at 3 months prior to death. Elderly, women, patients with high comorbidity, immigrants, living in urban areas or with high material deprivation were at increased risk of reporting severe scores.Despite an integrated symptom screening program, rates of severe patient-reported symptom scores prior to death were high for cancer outpatients. Patient subgroups at increased risk of severe symptom burden may benefit from targeted interventions. Ongoing review of routinely collected symptom data may be used to assess the supportive care needs and guide targeted interventions at the health-system level.