The impact of site of care (office clinic versus hospital outpatient) on treatment patterns in HER2-positive breast cancer.

Abstract

e11077 Background: This study examines treatment (tx) patterns in patients (pts) with breast cancer (BC) receiving trastuzumab (T) in a physician clinic (MD) & outpatient hospital (HOSP) setting. Methods: Pts ≥18 yrs with BC (≥2 claims with ICD-9-CM 174.xx, ≥30 days apart) and ≥2 T claims from 1/1/2006 to 12/31/2010 were identified from a large US commercial insurance claims database. Pts continuously enrolled for ≥ 6mths before & after index date (date of 1st T claim) were included. Pts receiving T at both sites of care, receiving T before the index date &/or pts with > 1 primary cancer were excluded. Metastatic (mBC) vs. early stage (ESBC) tx was identified by presence of ≥2 claims of metastases after index date. Pts were followed from index date to 30 days after the last infusion prior to a gap of ≥ 90 days, death, disenrollment, or end of study period. Pts were stratified by site of care- MD or HOSP. Descriptive & multivariate analyses were conducted to examine differences in tx patterns (duration and doses/mo) & number of missed doses during the tx period. Results: 2,823 BC pts receiving T were identified; 480 (17%) were treated for mBC. Most patients received T in the MD setting (94% ESBC pts and 87% of MBC pts). Compared to the MD setting, pts treated in the HOSP were more likely to be older (ESBC: 61 vs 53 yrs; MBC: 64 vs 54 yrs; each p <0.001) & have Medicare benefits (ESBC: 54% vs 7%; MBC: 63% vs 9%; each p <0.001). There was no difference in mean baseline Charlson comorbidity index in any group. Mean T duration in HOSP was significantly shorter vs MD among ESBC pts (303 & 333 days, p<0.05) but not MBC pts (313 for HOSP vs 355 days for MD, p>0.05). Compared to the MD setting, HOSP treated patients had more treatment gaps of 30-59 days (ESBC: 58% vs 25%; MBC 56% vs 27%; each p<0.001) and fewer infusions/month (ESBC: mean 1.45 vs 1.99; MBC 1.54 vs 2.07; each p<0.001). In multivariate analyses, infusion counts remained lower among HOSP treated patients (ESBC: IRR 0.74, CI 0.67-0.79; MBC: IRR 0.76, CI 0.66-0.87). Conclusions: MBC and ESBC pts treated in the MD setting were younger and received more infusions with fewer treatment gaps than HOSP pts. Further research assessing the impact of these differences in tx patterns on clinical outcomes is needed.