Introduction

Febrile neutropenia (FN), infection, death, and chemotherapy dose-reduction or delays are major consequences of myelosuppressive chemotherapy. The risk of FN is even greater for those who are 65 years and older, resulting in older patients being treated with lower doses of chemotherapy for cancers that typically respond well to treatment. Granulocyte growth stimulating factors (G-CSF), like filgrastim and pegfilgrastim, are FDA approved methods of reducing the risk of neutropenia and preventing dose reduction in those receiving chemotherapy. Current guidelines recommend that patients 65 years and older receiving chemotherapy with an intermediate to high (>10%) risk of developing FN should receive prophylactic G-CSF. With the population expected to age and cancer rates expected to rise, it is important to describe the trends and predictors of G-CSF use between the youngest old (65 to 75 years), middle old (75 to 85 years), and oldest old (> 85 years) cancer patients. Here, the G-CSF use in Texas from 2010 to 2019 and the personal characteristics associated with difference of use were assessed using retrospective Medicare data.

Methods

An all-cancer type cohort using 2010 to 2019 Texas Medicare data was selected. The primary outcome was whether the patient received G-CSF treatment at the initiation of chemotherapy to three days after the last dose of chemotherapy. Patient characteristics (ex: gender, race/ethnicity, metropolitan/non-metropolitan), G-CSF status, year of diagnosis, and type of cancer were analyzed using chi-squared tests and multivariable logistic regression models to estimate odds ratios (OR) and 95% confidence intervals (95% CI).

Results

The study cohort included 38,222 patients with cancer and 13.7% of those received G-CSF. When considering only breast, colorectal, esophageal/gastric, lung, ovarian, pancreatic, and prostate cancer or non-Hodgkin lymphoma (NHL), 25.0% of the patients received G-CSF. The proportion of patients receiving G-CSF for all cancers decreased over time (18.02% in 2010, 17.55% in 2014, 8.20% in 2019, p-value <0.0001). When looking at individual cancers, G-CSF use decreased across all types from 2010 to 2019, except for pancreatic and prostate cancer.

The oldest old and middle old had 69% (95% CI: 63% to 75%) and 25% (95% CI: 19% 31%) decreased odds, respectively, of receiving G-CSF compared to the youngest old patients when considering all cancers. This trend was not consistent across individual cancer types. Odds of G-CSF administration decreased with age for breast, colorectal, and pancreatic cancer, and increased with age for NHL and ovarian cancer (ref: Other Cancers). Males were less likely to receive G-CSF compared to women [OR (95% CI): 0.83 (0.76 to 0.89)], and black patients were more likely to receive G-CSF compared to white patients [OR (95% CI): 1.15 (1.01 to 1.31). No significant difference was found between those living in metropolitan versus non-metropolitan areas.

Conclusion

Only 13.7% of all patients with cancers received G-CSF, with the use rate decreasing over time across all cancer types except pancreatic and prostate cancer. The oldest old had the lowest odds of receiving G-CSF despite having the highest risk of FN. It is unclear if the declining rate, especially in the oldest old, reflects G-GSF underuse in the geriatric population or the use of new bone-marrow-sparing chemotherapy.