Background: Prescribing drugs outside of the label indication is legal and may reflect standard practice; however, some off-label use may be inappropriate. This study measured the prevalence and safety of off-label use both in accordance with practice guidelines and inconsistent with practice guidelines in older patients with breast cancer. Patients and Methods: The SEER-Medicare data set was used to identify women diagnosed with breast cancer. Intravenous chemotherapy was identified using Medicare claims and classified as either on-label, off-label but included in the NCCN Clinical Practice Guidelines in Oncology (NCCN Guidelines) for Breast Cancer (“off-label/supported”), or off-label and not included in the NCCN Guidelines (“off-label/unsupported”). Hospitalization/emergency department (ED) admission rates were compared. Results: A total of 13,347 women were treated with 16,127 regimens (12% of women switched regimen); 64% of regimens were off-label/supported, 25% were on-label, and 11% were off-label/unsupported, and hospitalization/ED admission occurred in 27%, 25%, and 32% of regimens, respectively (P<.0001). Drugs never included in the NCCN Guidelines for Breast Cancer accounted for 19% of off-label/unsupported use (1% of total use). Conclusions: Off-label use without scientific support was not common, whereas 64% of use was off-label/supported, reflecting the fact that widely accepted indications are often not tested in registration trials. Off-label/supported use will likely increase as more drugs are expected to have activity across cancer sites, and therefore understanding the implications of such use is critical.
Correspondence: Anne A. Eaton, MS, Memorial Sloan Kettering Cancer Center, Department of Epidemiology and Biostatistics, 485 Lexington Avenue, 2nd Floor, New York, NY 10017. E-mail: email@example.com