Objectives: Evidence suggests that continued trastuzumab therapy beyond progression (TBP) may provide additional survival benefit. Within the framework of an observational prospective study of patients with advanced/metastatic breast cancer receiving trastuzumab in routine clinical practice, we had the opportunity to examine the effect of TBP in a large population.
Patients and methods: Among a total of 1843 trastuzumab-treated patients, a sub-cohort of 418 fulfilled the selection criteria for the TBP analysis: 261 continued trastuzumab and 157 discontinued. Logrank tests and Cox models were used to compare survival and identify prognostic factors.
Results: Survival from progression was significantly longer in those patients continuing trastuzumab treatment beyond disease progression (TBP: median 22.1 months; no TBP: median 14.9 months; HR = 0.64; P = 0.00021). In addition to TBP, a positive endocrine receptor status, a longer relapse-free interval, no visceral metastasis, no concomitant chemotherapy during first-line treatment, and first-line response were independently significant prognostic variables for longer survival on multivariate analysis.
Conclusion: The hitherto limited evidence for TBP benefit from randomized studies was confirmed. While a number of strong disease-related predictors for survival after first progression could be identified, the positive effect of trastuzumab continuation retained statistical significance in a multivariate model.
Keywords: Breast cancer; Trastuzumab; Treatment beyond progression.
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