The main aim of the experiment was to estimate unplanned hospitalization rates and to describe the reasons for hospitalization in a population-based cohort recently diagnosed with cancer. Reducing acute care use is an important strategy for improving value in cancer care. However, little information is available to describe and compare population-level hospital use across cancer types. California Cancer Registry data linked with administrative inpatient data were used to examine unplanned hospitalization among individuals diagnosed with cancer between 2009 and 2012.

Approximately 67% of hospitalizations in the year after diagnosis were unplanned, 35% of newly diagnosed individuals experienced an unplanned hospitalization, and 67% of unplanned hospitalizations originated in the emergency department (ED). Non Malignancy principal diagnoses most frequently associated with unplanned hospitalization included infection (15.8%) and complications of a medical device or care (6.5%). We excluded individuals who were younger than 18 years of age at diagnosis (1.1%), who were diagnosed with in situ disease (9.7%), who did not have an OSHPD ID number for linkage (either because they had never had an OSHPD encounter or because they lacked a valid SSN; 9.5%), or who had multiple values of the variables needed for uniquely identifying individuals and hospital encounters (< 1%). The final eligible sample included n = 412,850 adults with cancer.

Many unplanned hospitalizations originate in the ED and are associated with potentially preventable admission diagnoses. Efforts to reduce unplanned hospitalization might target subgroups at higher risk and focus on the ED as a source of admission.