Developing a multimorbidity prognostic score in elderly patients with solid cancer using administrative databases from Italy

Aims: To develop and to validate a Cancer Multimorbidity Score (CMS) predictive of mortality in elderly patients affected by solid tumor, by using population-based administrative Italian databases. Methods: Through administrative databases of Lombardy Region (Northern Italy), a cohort of patients aged ≥65 years with a new diagnosis of solid tumor during the period 2009–2014 was identified. Sixty-one conditions and diseases, measured from hospital inpatient diagnosis and outpatient drug prescription within 2 years before cancer diagnosis in a training set randomly including 70% of the cohort patients were tested to predict 5-year mortality using a Cox regression model. Regression coefficients were used for assigning a weight to the predictive conditions, selected by the LASSO method. Weights were summed up in order to produce an aggregate score (the CMS). CMS performance was evaluated on a validation set, including the remaining 30% of the cohort patients, in terms of discrimination and calibration. Results: The study cohort included 148,242 cancer patients. Thirty conditions were selected as independent predictors of 5-year mortality and were included in the computation of the CMS. The area under the receiving operating characteristics curve was 0.68, becoming 0.71 when considering 1-year mortality as outcome and reaching values of 0.74 and 0.81 when focusing on patients with breast and prostate cancer, respectively. A strong increasing trend in mortality was observed with increasing CMS value. Conclusions: CMS represents a new useful tool for identifying high-risk elderly cancer patients in everyday clinical practice, as well as for risk adjustment in clinical and epidemiological studies.