Chronic comorbid conditions associated with risk of febrile neutropenia in breast cancer patients treated with chemotherapy.

Chemotherapy-induced febrile neutropenia (FN) is associated with increased patient mortality and health care costs. Comorbid conditions such as liver and renal dysfunction have been linked to increased risk of FN. However, the effects of other chronic comorbid conditions on risk of FN have not been well studied. To examine the association between chronic comorbid conditions and FN in breast cancer patients, we identified incident breast cancer patients from 2000 to 2009 treated with chemotherapy at Kaiser Permanente Southern California, a large managed care organization. Patients who received primary prophylactic granulocyte colony-stimulating factor (G-CSF) were excluded. We assessed history of comorbid conditions prior to cancer diagnosis using ICD-9 codes and disease registries. FN events were identified in the first chemotherapy cycle using a combination of ICD-9 codes and hospital discharge diagnoses. For each comorbid condition, propensity scores that included patient characteristics and other predisposing comorbid conditions were calculated and adjusted for in Cox models to determine associations between that comorbid condition and FN. We also evaluated secondary models that additionally adjusted for cancer stage, baseline absolute neutrophil count (ANC), chemotherapy regimen, and dose reductions. A total of 7,127 breast cancer patients were included; median age was 55 years, and the majority had localized (47 %) or regional (49 %) disease at diagnosis. In the first chemotherapy cycle, 335 (4.7 %) patients developed FN. Congestive heart failure (HR = 3.0; 95 % CI: 1.3-5.9), osteoarthritis (HR = 2.0; 95 % CI: 1.4-2.8), previous cancer (HR = 3.4; 95 % CI: 1.2-7.5), and thyroid disorder (HR = 1.6; 95 % CI: 1.1-2.3) were associated with increased risk of FN. These estimates were similar to those from secondary models that also adjusted for additional cancer and treatment-related covariates. Our findings suggest that several chronic comorbid conditions may be associated with risk of FN. This information, if confirmed by others, may aid clinical decision making with respect to use of prophylactic G-CSF during chemotherapy treatment.