Association of driving distance to clinic with treatment route and dosing for metastatic breast cancer.

e13077 Background: High travel burden is associated with worse cancer outcomes. Travel distance also influences cancer treatment; for example, women who travel further for radiation therapy less often have breast conserving surgery. For women with metastatic breast cancer, we tested the hypothesis that the route and dosing frequency of systemic therapies, which set the cadence of clinic visits, vary with the distance traveled for care. Methods: The Stanford University Cancer Institute (SCI) is an NCI-designated cancer center, serving a catchment area of 7.8 million people over 35,000 square kilometers (km). We used the Oncoshare database, which integrates data from electronic medical records and the California Cancer Registry, to identify those with metastatic hormone receptor (HR)-positive, HER2-negative breast cancer (MBC) treated at the SCI from 2010-2024. Eligibility criteria were >3 medical oncology outpatient visits and receipt of first line metastatic treatment at the SCI. The first line regimen was categorized as low- or high-contact, defined by the route of administration (oral vs non-oral) and the dosing interval (high >21 days) of non-oral therapies. Using propensity score weighting with covariate balancing propensity scores, we assessed the association of driving distance from home to clinic with the route of administration (oral vs non-oral) and dosing frequency (high vs low) of the initial metastatic treatment. This model included age at metastatic diagnosis, year of metastatic diagnosis, de novo metastatic presentation, insurance status, rurality quintile, body mass index, race and ethnicity. Results: Of 399 patients who met eligibility, 204 were non-Hispanic White (51%), 27% Asian, 11% Hispanic, and 3.5% Black. Most (238, 60%) had private/commercial insurance and half (209, 52%) resided in census tracts that ranked at the highest socioeconomic quintile (Q) statewide. Driving distance from home to oncology clinic ranged from 0 to 3,949 km, with median (Q1, Q3) of 33 (15, 87) km; 223 patients (55.9%) resided within 40 km and 310 (77.7%) within 100 km. Of the 165 patients (41%) who started oral therapy, subsequent treatments were: high-frequency non-oral (n=35), low-frequency non-oral (n=25), oral only (n=68), and unknown (n=37). Patients with a driving distance ≥100km were more likely to receive oral (vs non-oral) systemic therapy (OR=1.58, 95% CI: 1.06-2.35, p=0.025) and low (vs high) frequency non-oral therapy (OR=3.06, 95% CI: 1.07-9.26, p=0.045). The median breast cancer-specific survival was 39.9 (range: 0.72-130.3) months and did not vary significantly with driving distance (HR 1.14 95% CI: 0.63-2.04, p=0.668). Conclusions: In those with MBC, greater driving distance from home to clinic was associated with lower-contact treatment, suggesting that oncologists tailor therapy to reduce travel burden. This may guide patient-centered treatment selection to reduce travel burden.