Continued use of trastuzumab beyond disease progression in the national comprehensive cancer network: should we practice ahead of the evidence?

BACKGROUND: The role of continued trastuzumab after progression in women with human epidermal growth factor receptor (HER)-2+ metastatic breast cancer is controversial. Controlled clinical trials that establish a benefit from continued trastuzumab have been difficult to complete.
METHODS: In the National Comprehensive Cancer Center Network (NCCN) Breast Cancer Outcomes Database, we identified women treated with trastuzumab for metastatic or relapsed HER-2+ breast cancer at eight NCCN centers who subsequently progressed. Patients were eligible for this analysis if they initiated treatment at an NCCN institution between July 1997 and December 2004, received trastuzumab-containing treatment, and progressed while on therapy. We calculated the proportion of patients who received trastuzumab after progression, and in a multivariate analysis assessed the association of patient and provider characteristics with continued trastuzumab therapy.
RESULTS: Our final cohort consisted of 218 women who experienced disease progression while on trastuzumab-containing therapy. Of these, 168 (77%) continued trastuzumab. Of these, 36 patients (17%) received therapy as part of a clinical trial. The only factors significantly associated with continuation of trastuzumab beyond progression were the presence of bone metastases and more recent year of development of progressive disease.
CONCLUSIONS: Prior to the availability of any high-quality evidence supporting this practice, over three quarters of patients treated with trastuzumab for HER-2+ metastatic breast cancer at eight NCCN centers continued therapy beyond progression. Further work is needed to understand how physicians adopt new treatments when there is ambiguity surrounding their benefit.