We have developed a new cancer-specific scoring system for solid cancer patients with suspected infection. This new system had a strong discriminative power to predict 30-day mortality, showing a C-statistic of 0.799 in the development cohort and 0.793 in the validation cohort. In comparison with existing scoring systems, the new scoring system was superior to SOFA (C-statistic, 0.723), qSOFA (C-statistic, 0.596), and SIRS (C-statistic, 0.547). To our knowledge, our new prognostic model is the first cancer-specific scoring system to predict mortality for cancer patients with suspected infection.
This new scoring system was developed and validated in two groups of similar size, recruited at different times in the same hospital. There was no significant difference in baseline characteristics except anti-cancer treatment between the two development and validation cohorts. In our study, the overall 30-day mortality rate was 22.5%. There was a difference in 30-day mortality between development and validation cohorts (19.3% vs. 25.6%, P = 0.024). However, the C-statistic (0.799 in the development cohort, 0.793 in the validation cohort) of our new scoring system showed a good discriminative capability to predict 30-day mortality in both groups. The Hosmer–Lemeshow goodness to fit test suggested that predicted mortality reflects true mortality, and thus our scoring system is well-calibrated. Several prognostic scoring systems have been used to predict prognosis in patients with infection.14–16 SOFA is one of the most frequently validated systems and is an excellent predictor of mortality.17 However, most of the SOFA studies were on non-cancer patients, and studies on those with cancer were limited with inconsistent results8,9,18. In a recent study, SOFA had good discriminative power in patients with cancer and was superior to qSOFA.8 In two previous studies, both SOFA and qSOFA showed weak discriminative ability with a C-statistic of < 0.7 in predicting mortality for cancer patients with infection.9,18 As shown in this study, our new scoring system can be a good alternative to predict mortality in cancer patients with suspected infection.
The new cancer-specific scoring system consisted of six components: ECOG PS, SpO2, creatinine, total bilirubin, CRP, and lactate. These six components reflect the underlying condition of patients with cancer and acute responses to infection. The ECOG PS of these patients has been considered as an essential prognostic factor.19,20 ECOG PS had the highest score distribution among the new scoring system variables in our study. Performance status is affected by many factors such as the patients’ age, cancer stage, and side effects of anti-cancer treatment. Patients who have a poor PS and limited functional capacity tend to have more difficulty tolerating rigorous cancer treatments. These patients have less favorable outcomes than those with a better PS, regardless of distant metastasis or treatments given.21 In this study, ECOG PS was a significant prognostic factor in cancer patients with suspected infection, whereas advanced stage or anti-cancer treatment were not. Lactate represents tissue hypoperfusion, and lactate > 2 mmol/L was introduced as diagnostic criteria of septic shock.22 Furthermore, lactate has been shown to have prognostic power in cancer patients with sepsis.8 Increased CRP is an indicator of inflammation in patients with sepsis. A recent study reported that CRP carries significant independent prognostic information.23, which was consistent with the results of our study; elevated CRP was associated with increased 30-day mortality in cancer patients with suspected infection. Creatinine and total bilirubin are indicators of hepatic and renal function, which are also components of SOFA.24 SOFA included PaO2/FiO2 as a respiratory indicator. We used SpO2 in place of PaO2/FiO2 given the ease to continuously and noninvasively obtain at the ER without drawing arterial blood. A previous study reported that SpO2 was consistently associated with mortality in patients with septic shock.25
This study has several limitations. First, it was conducted in a single hospital, which was a tertiary referral cancer center. There may have been a high proportion of severe disease. In our study, the 30-day mortality rate was 22.5%; however, in the US population report, cancer-related sepsis hospitalizations had high in-hospital mortality of 27.9%.1 Second, this study used a retrospective design. However, there was very few missing data. In our hospital, there is a separate ER for patients with cancer26, in which data collection and the treatment process are standardized. Lastly, we included only solid tumors and excluded hematologic malignancies in this study. Generalization of applying the new scoring system to patients with hematologic malignancies is therefore difficult. Many studies have shown that prognosis of patients with solid tumors and hematologic malignancies is quite different.27,28 We consider that the prognostic model would have to be different to assess these two groups appropriately.
In conclusion, the new scoring system had a robust discriminative capability to predict prognosis in cancer patients with suspected infection. This new scoring system can be a good alternative for patients with cancer compared with existing scoring systems.