BackgroundOver the last decades, a decrease in short-term mortality in cancer patients admitted to the ICU has been described in literature. However, it is unclear whether this decrease also results in a decrease in long-term mortality. Therefore, we examined the 1-year mortality of cancer patients (either haematological or solid) with an unplanned ICU admission.Methods and dataAll adult patients registered in the National Intensive Care Evaluation registry with an unplanned ICU admission in the Netherlands between 2008 and 2017 were included. The primary outcome was 1-year mortality, analysed with a mixed-effects cox-proportional hazard regression. We examined the trend in mortality rates over the inclusion period. Furthermore, we compared the 1-year mortality of cancer patients to that of patients without cancer. ResultsWe included 470,305 patients: 10,401 with haematological cancer, 35,920 with solid tumours, and 423,984 without cancer. The 1-year mortality rates were 60.1%, 46.2%, and 28.3% (p<0.01), respectively. While no statistically significant trend was found (p=0.58), a visual inspection of the graph showed a slightly decreasing trend in 1-year mortality over the inclusion period. Although we found a statistical significant difference in 1-year mortality in patients with a solid tumour (p<0.01), visual inspection showed a wide variety per year. We found a decreasing trend in 1-year mortality in ICU patients without a malignancy (p<0.01). Cancer patients surviving their critical illness and hospital admission had a 30% mortality at 1 year. ConclusionThe 1-year mortality in cancer patients with an unplanned ICU admission (either haematological or solid) was significantly higher than that of patients without cancer. A visual inspection showed a slight decrease in 1-year mortality in haematological patients, while the 1-year mortality in patients with a solid tumour varied per year. After hospital discharge, a considerable part of the patients with a malignancy died within 1 year. Physicians should discuss the long-term prognosis after an ICU admission with patients and relatives in order to manage treatments and expectations. Future research should focus on identifying cancer patients who will benefit from an ICU admission.