Treatment of early-stage human epidermal growth factor 2-positive cancers among medicare enrollees: age and race strongly associated with non-use of trastuzumab.

Adjuvant trastuzumab for human epidermal growth factor receptor-2 (HER2)-positive breast cancer is highly efficacious regardless of age. Recent data suggested that many older patients with HER2-positive disease do not receive adjuvant trastuzumab. Nevertheless, some of this 'under-treatment' may be clinically appropriate. We used Surveillance, Epidemiology and End Results (SEER)-Medicare data to identify patients aged ≥ 66 with stage ≥ Ib-III, HER2-positive breast cancer diagnosed during 2010-2011 (HER2 status available) who did not have a history of congestive heart failure. We described all systemic treatments received and sociodemographic and clinical characteristics associated with treatment patterns. Among 770 women 44.4 % did not receive trastuzumab, including 21.8 % who received endocrine therapy only, 6.3 % who received chemotherapy (±endocrine therapy) and 16.2 % who did not receive any systemic therapy. In addition to age and grade, race was strongly associated with non-use of trastuzumab (64.4 % of Non-Hispanic blacks vs. 43.6 % of whites did not receive trastuzumab, adjusted ORNon-Hispanic black vs. white = 3.14, 95 %CI = 1.38-7.17), and many patients with stage III disease did not receive trastuzumab. Further, 16.2 % of patients did not receive any systemic treatment and this occurred more frequently for black patients. Over 40 % of older patients with indication to receive adjuvant trastuzumab did not receive it and nearly 20 % of these patients did not receive any other treatment. Although treatment omission may be appropriate in some cases, we observed concerning differences in trastuzumab receipt, particularly for black women. Strategies to optimize care for older patients and to eliminate treatment disparities are urgently needed.