Health care utilization and costs by site of service for nonmetastatic breast cancer patients treated with trastuzumab.

Background: Adjuvant trastuzumab treatment is administered to early stage breast cancer patients in physician office (POV) or hospital outpatient (HOP) settings.

Objective: To identify treatment patterns, utilization, and costs by site of care (POV vs. HOP) of patients with adjuvant treatment of breast cancer with trastuzumab.

Methods: This retrospective analysis identified adult, female breast cancer patients who initiated trastuzumab treatment (index date) from a large U.S. claims database. Inclusion criteria also required ≥ 2 claims for both trastuzumab (from July 1, 2006, to July 31, 2012) and breast cancer (during 6-month pre-index baseline period), no evidence of metastatic breast cancer or other cancers in the baseline period, and continuous enrollment with commercial or Medicare Advantage coverage 6 months pre- and post-index, except that patients who died during follow-up were retained. Patients with evidence of trastuzumab receipt during the baseline period or more than 1 site of care during follow-up were excluded. Patients were stratified by site of care and were followed from index date to 30 days after the last trastuzumab infusion prior to a gap ≥ 90 days, death, disenrollment, or end-of-study period. Differences in treatment patterns between the POV and HOP cohorts were assessed by t-test and chi-square test. The relationship between site of care and health care costs was modeled with a generalized linear model with gamma distribution and log link, and the number of trastuzumab infusions was modeled with negative binomial regression controlling for log follow-up time. All models were adjusted for age, baseline comorbidity score, and insurance type.

Results: Of the 3,439 breast cancer patients identified, 77.6% (2,669) received adjuvant trastuzumab in the POV setting. Mean age (53.7 years) and baseline comorbidity score (3.91) were similar among cohorts; a higher percentage of POV versus HOP patients had commercial insurance (91.1% vs. 86.4%, P < 0.001). Compared with the POV cohort, HOP patients had a shorter mean duration of trastuzumab treatment (324.8 vs. 343.0 days, P < 0.001); more treatment gaps (30-59 day gap: 67.4% vs. 24.1%, P < 0.001); and fewer trastuzumab infusions per month (1.37 vs. 1.98, P < 0.001) during follow-up. In multivariate analysis, the monthly count of trastuzumab infusions in the HOP cohort was lower than the POV cohort (incidence rate ratio = 0.693; 95% CI = 0.672-0.715). Adjusted per patient per month total health care costs were 53.6 % higher in the HOP setting (cost ratio = 1.536, 95% CI = 1.472-1.604).

Conclusions: Breast cancer patients treated with adjuvant trastuzumab in the HOP setting had a shorter duration of trastuzumab treatment and fewer trastuzumab infusions but incurred higher monthly total costs than patients treated in the POV setting.