A validated risk model for early neutropenic events in older cancer patients receiving systemic chemotherapy
9036 Background: A prospective, nationwide study was undertaken to develop and validate a risk model for early neutropenic events (NE) in older cancer patients undergoing chemotherapy. Methods: 1,386 patients =65 years of age with lung, breast, colorectal, ovarian cancer or lymphoma were prospectively registered at 117 randomly selected sites. Data on up to 4 cycles were collected upon initiation of chemotherapy. A logistic regression model for cycle 1 NE consisting of febrile neutropenia (FN; fever/infection and absolute neutrophil count nadir <1x109/L) or severe neutropenia (SN; neutrophils <.5x109/L) was derived on 1,378 patients with available data. Validation was performed using a split sample random selection process. Results: No significant differences in distribution of NE or predictive factors were observed between derivation dataset (n=922) and validation dataset (n=464). Major independent baseline clinical risk factors for cycle 1 NE in the derivation model (DM) included: anthracycline based regimens (p<.001), non-chemotherapy immune-modulatory agents (p=.003), elevated bilirubin (p=.016), reduced glomerular filtration rate (p<.001), cancer type (p=.02), planned relative dose intensity =85% (p=.027), and regimens containing cyclophosphamide (p<.001), etoposide (p=.002) or ifosfamide (p=.032). Reduced risk of cycle 1 NE was associated with myeloid growth factor (MGF) prophylaxis (p<.001). DM R2 was 0.478 and c-statistic 0.88 [95% CI 0.86–0.91; p<.001]. At median predicted risk of cycle 1 NE of 7%, model test performance (MTP) showed: sensitivity 90%; specificity 59%; and predictive value positive and negative of 32% and 97%, respectively. Cycle 1–4 FN risk in the DM was 16.6% and 3.3% among high and low risk patients, respectively. The validation model (VM) R2 was 0.508 and c-statistic 0.89 [95% CI: 0.86–0.93; p<.001]. MTP in the VM demonstrated: sensitivity 90%; specificity 65%; predictive value positive and negative of 36% and 97%, respectively. Cycle 1–4 FN risk in the VM was 16.8% and 1.6% in high and low risk patients, respectively. Conclusions: This validated risk model demonstrated good discrimination between older cancer patients at decreased risk for NE, and those at increased risk who may benefit from targeted prophylaxis with MGF. No significant financial relationships to disclose.