External Validation of Risk Factors for Unplanned Hospitalization in Older Adults With Advanced Cancer Receiving Chemotherapy

Background: Older adults (age >= 65 years) receiving chemotherapy are at risk for hospitalization. Predictors of unplanned hospitalization among older adults receiving chemotherapy for cancer were recently published using data from a study conducted by the Cancer and Ag-ing Research Group (CARG). Our study aimed to externally validate these predictors in an independent cohort including older adults with advanced cancer receiving chemotherapy. Methods: This validation cohort included patients (n=369) from the GAP70+ trial usual care arm. Enrolled patients were aged >= 70 years with incurable cancer and were starting a new line of chemotherapy. Previously identified risk factors proposed by the CARG study were >= 3 comorbidities, albumin level <3.5 g/dL, creatinine clearance <60 mL/min, gastrointestinal cancer,>= 5 medications, requiring assistance with activities of daily activities (ADLs), and having someone available to take them to the doctor (ie, presence of social support). The primary outcome was unplanned hospitalization within 3 months of treatment initiation. Multivariable logistic regression was applied including the 7 identi-fied risk factors. Discriminative ability of the fitted model was performed by calculating the area under the receiver operating characteristic (AUC) curve. Results: Mean age of the cohort was 77 years, 45% of patients were women, and 29% experienced unplanned hospitalization within the first 3 months of treatment. The proportions of hospitalized patients with 0-3, 4-5, and 6-7 identified risk factors were 24%, 28%, and 47%, respec-tively (P=.04). Impaired ADLs (odds ratio, 1.76; 95% CI, 1.04-2.99) and albumin level <3.5 g/dL (odds ratio, 2.23; 95% CI, 1.37-3.62) were significantly associated with increased odds of unplanned hospitaliza-tion. The AUC of the model, including the 7 identified risk factors, was 0.65 (95% CI, 0.59-0.71). Conclusions: The presence of a higher num-ber of risk factors was associated with increased odds of unplanned hospitalization. This association was largely driven by impairment in ADLs and low albumin level. Validated predictors of unplanned hospi-talization can help with counseling and shared decision-making with patients and their caregivers.