P5-18-08: A Comparative Effectiveness Analysis of Trastuzumab Persistence between Two Adjuvant Breast Cancer Treatment Regimens among US Health Plan Enrollees.
Authors: D Lalla, EM Pelletier, S Goodman, M Brammer, VF Schabert
Journal: Cancer Research (2011)

Abstract Background Approved US indications for trastuzumab include adjuvant treatment of HER2−overexpressing breast cancer in anthracycline-based (ACTH) or non-anthracycline-based (TCH) regimens. The objective of this study was to compare trastuzumab persistence across adjuvant breast cancer treatment regimens for US health plan enrollees. Materials and Methods: This retrospective cohort study using the IMS LifeLink™ Health Plan Claims Database included adjuvant breast cancer patients, defined as those with a mastectomy or lumpectomy and a primary breast cancer diagnosis (index diagnosis) from 1/1/2006 to 12/31/2008. Additional inclusion criteria were: aged ≥18 years; a second primary breast cancer diagnosis ≤90 days of the first; no other primary or secondary neoplasms ≤180 days before or ≤90 days after the index diagnosis; a first trastuzumab claim (index claim) and ≥1 carboplatin, cyclophosphamide, taxane, or anthracycline claim ≤210 days of the index diagnosis; and no trastuzumab claim before the index diagnosis. Regimens were classified as ACTH (doxorubicin, cyclophosphamide, a taxane, trastuzumab) or TCH (docetaxel, carboplatin, trastuzumab) from therapies observed after the index claim. Trastuzumab persistence (days from the index claim to earliest of trastuzumab discontinuation, a new malignant neoplasm, end of plan enrollment, 360 days after the index claim, or end of available data) was reported for patients with ≥2 trastuzumab claims and compared across regimens using the Kaplan-Meier estimator and Cox proportional hazards models. Results: 550 breast cancer patients met all study criteria (291 ACTH, 259 TCH, 46 unassigned); patients receiving TCH were older (median 52 vs. 50 years; P=0.018). For years 2006–2008, the annual share of the cohort initiating ACTH decreased from 69.3% to 35.2%; patients initiating TCH increased from 26.7% to 56.5%. Patients receiving ACTH were treated with trastuzumab for fewer days (mean=256, median=334) versus patients on TCH (mean=282, median 344, P=0.018). Fewer patients on ACTH remained on trastuzumab at day 90 (83% vs. 91%), day 180 (71% vs. 79%), day 270 (61% vs. 72%), and day 360 (20% vs. 26%). Compared to patients on TCH, patients on ACTH continued to be treated with trastuzumab for a shorter duration post-index after adjusting for age, region, plan type, prescriber specialty, and comorbidities (HR=0.77, 95% CI [0.63, 0.95]; P=0.016). Discussion: The share of adjuvant breast cancer patients initiating TCH increased from 2006 to 2008, while use of ACTH decreased over the same time period, and patients treated with TCH remained on trastuzumab for a longer period of time. From a clinical standpoint, patients derive maximum benefit from their medications when they are persistent long-term, which can lead to economic benefits with regards to lower overall healthcare costs. Further analyses will evaluate whether adjuvant breast cancer regimens differ in weight-adjusted cumulative trastuzumab doses received during therapy. Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P5-18-08.