Abstract
We addressed trastuzumab emtansine (T-DM1) efficacy in HER2+ metastatic breast cancer patients treated in real-world practice, and its activity in pertuzumab-pretreated patients. We conducted a retrospective, observational study involving 23 cancer centres, and 250 patients. Survival data were analyzed by Kaplan Meier curves and log rank test. Factors testing significant in univariate analysis were tested in multivariate models. Median follow-up was 15 months and median T-DM1 treatment-length 4 months. Response rate was 41.6%, clinical benefit 60.9%. Median progression-free and median overall survival were 6 and 20 months, respectively. Overall, no differences emerged by pertuzumab pretreatment, with median progression-free and median overall survival of 4 and 17 months in pertuzumab-pretreated (p=0.13), and 6 and 22 months in pertuzumab-naïve patients (p=0.27). Patients who received second-line T-DM1 had median progression-free and median overall survival of 3 and 12 months (p=0.0001) if pertuzumab-pretreated, and 8 and 26 months if pertuzumab-naïve (p=0.06). In contrast, in third-line and beyond, median progression-free and median overall survival were 16 and 18 months in pertuzumab-pretreated (p=0.05) and 6 and 17 months in pertuzumab-naïve patients (p=0.30). In multivariate analysis, lower ECOG performance status was associated with progression-free survival benefit (p<0.0001), while overall survival was positively affected by lower ECOG PS (p<0.0001), absence of brain metastases (p 0.05), and clinical benefit (p<0.0001). Our results are comparable with those from randomized trials. Further studies are warranted to confirm and interpret our data on apparently lower T-DM1 efficacy when given as second-line treatment after pertuzumab, and on the optimal sequence order.
Highlights
HER2 is overexpressed/amplified in about 15-20% of breast cancers, and is related to poor prognosis [1, 2]
We retrospectively identified 250 HER2+ metastatic breast cancer (MBC) patients treated with trastuzumab emtansine (T-DM1) from February 2013 through July 2016 at 23 Italian cancer centers
Median overall survival (OS) was 20 months (95%CI, 13-27) as first-line, 26 months (95%CI, 15.6-36.3) in second-line, and 17.8 months (95%CI, 14-29) when T-DM1 was administered in more advanced lines (Table 2) (p=0.60)
Summary
HER2 is overexpressed/amplified in about 15-20% of breast cancers, and is related to poor prognosis [1, 2]. One-hundred and twenty-five pertuzumab-naïve patients receiving T-DM1 beyond the second-line had a mPFS of 6 months (95%CI, 4-7), and a mOS of 17 months (95%CI, 12-22), with no relevant statistical differences (p=0.05 and p 0.30, respectively) (Figure 2, Supplementary Table 4).
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