This study is one of the largest single-center studies of ICU patients with HM and includes a considerable proportion of patients with HSCT. To the best of our knowledge, this is the first study in Taiwan to report the prognostic factor related to short-term outcomes in critically ill patients with HM.
The ICU and hospital mortalities in our study were 54.1% and 67.8%, respectively. A recent single-center study from Germany reported ICU mortalities rates of 45.2% (in 2009–2012 cohort) and 66.7% (in 2013–2016 cohort) at different time periods (23). To a wider extent, the previously published ICU and hospital mortality rates in patients with HM who were admitted to the ICU ranged from 24.8–66% and from 43–77%, respectively (15). The differences in mortality observed between studies including ours may be explained by variations in disease severity, admission and discharge criteria, treatment decisions, and the implementation of end-of-life decisions. Notably, the disease severity at ICU admission was higher in our patient than those reported in previous studies. With persisting high overall mortality, the ICU mortality decreased during the years of observation (Fig. 3), which may be attributable to better supportive care, improved management of sepsis (24), and acute respiratory distress syndrome (ARDS) (25). Although this finding was not statistically significant, the trend of decreased ICU mortality was consistent with previous studies (4–6).
Several prognostic factors for critically ill patients with HM were published by previous studies, and some were considered “classical” risk factors. Neutropenia, poor performance status, advanced cancer status, invasive mechanical ventilation, vasopressors, renal replacement therapy, HSCT, and increasing time in hospital before ICU admission have been shown to be useful predictors of ICU and hospital mortality rates in previous studies. Scoring systems such as the APACHE II and SAPS II were widely validated in previous studies. However, in our study, only the initiation of renal replacement therapy in the ICU and SOFA scores were independently associated with ICU mortality. The area under the ROC curve to predict ICU mortality increased to 0.81 (95% CI, 0.75–0.0.87) when the two variables were combined. This result was consistent with previous results that the presence of organ failure was the major factor of poor outcome (10, 14, 17, 20, 22, 26). In previous studies, the SOFA score was less validated in predicting the ICU outcome of critically ill patients with HM than the APACHE II and SAPS II. However, the SOFA scoring system is a less cumbersome tool in clinical practice and had been applied in determining the duration of time-limited trials of intensive care for critically ill patients with cancer (27). Our result encourages clinicians to use the SOFA score for triage decisions and time-limited trial in the patient group.
Early ICU admission of patients identified as being at risk of multiorgan failure had been recommended (4), and early intervention before ICU admission in critically ill cancer patients was proved to decrease in-hospital mortality (28). In our study, 68 patients (29.2%) were admitted to the ICU directly from the emergency department, of whom 49 survived the ICU stay. Time in hospital before ICU admission was significantly higher in the non-survivor group. Although we could not clarify the relationship between time in hospital before ICU admission and delayed ICU admission, our data supports the concept that early and timely admission to the ICU in patient identified as high risk of severe organ dysfunction (29). Thus, underlying HM disease, neutropenia, and even post HSCT status should not be considered as a reason for delayed endotracheal tube intubation or ICU admission.
Thirty-one patients (13.3%) had pathologically confirmed HMs in the ICU, and in 15 patients, administration of antineoplastic agents was initiated as a first-line treatment in the ICU. Of all the patients, 11 survived the ICU stay and 6 were still alive 180 days after ICU discharge. It is crucial that a hematologic specialist is involved in the ICU management (30). With the emergence of novel agents for treating HMs, specific therapies under the recommendation of a hematologic specialist may lead to improved outcome and long-term survival (31).
This study has several limitations. First, this was a retrospective single-center study. However, it analyzed data collected over 40 months from one of the largest medical centers in Taiwan and enrolled a considerable number of patients. Second, the mortality rate was higher in our patients than in those in previous studies (15). However, the severity index was higher in our patients, and the crude mortality was difficult to compare from those in other studies because of the variations in admission and discharge criteria. Third, we could not demonstrate the impact of time-limited trials, which was a widely known concept in the management of critically ill patients with cancer (27). The decision of whether to treat these patients in the ICU remains difficult and needs evaluation on a patient-to-patient basis. A recent multicenter retrospective cohort study with 1097 patients in the Netherlands suggested that even in multiorgan failure, it should not be used as a criterion for excluding patients with HMs from admission to the ICU (8).
Future studies should focus on ICU-acquired infections in this patient group; further clarifying the relationship between time in hospital before ICU admission and delayed ICU admission; long-term outcomes after ICU discharge, including quality of life; and new epidemiology and challenges in ICU admission in the era of immunotherapy.