Disparities of Trastuzumab Use in Resource-Limited or Resource-Abundant Regions and Its Survival Benefit on HER2 Positive Breast Cancer: A Real-World Study from China.

BACKGROUND: Trastuzumab is a key component of therapy for human epidermal growth receptor 2 (HER2) positive breast cancer. Because real-world data are lacking, the present research was conducted to evaluate the actual use of and the effectiveness of trastuzumab in the real world in China.

METHODS: Inpatients with HER2 positive invasive breast cancer from 13 hospitals in Eastern China (2010-2015, n  = 1,139) were included in this study. We aimed to assess the actual use of trastuzumab and to evaluate potential efficacy from trastuzumab in real-world research.

RESULTS: Of 1,017 patients with early stage breast cancer (EBC), 40.5% (412/1,017) received trastuzumab therapy. Patients with EBC in resource-abundant regions (gross domestic product per capita >$15,000 and trastuzumab included in Medicare) are more likely to receive trastuzumab than those in resource-limited regions (37.3% vs. 13.0%, p  < .05). After metastasis, 50.8% (366/720) patients received trastuzumab as their first-line therapy. More than 10% of patients with metastatic breast cancer (MBC) continued trastuzumab therapy after twice progression in resource-abundant regions, whereas more than 40% of patients never received any trastuzumab therapy during the whole course of therapy in resource-limited regions. Overall, the improvement in survival for trastuzumab versus non-trastuzumab was substantial in EBC (hazard ratio [HR] = 0.609, 95% confidence interval [CI]: 0.505-0.744) and in MBC (HR = 0.541, 95% CI: 0.418-0.606). This association was greater for patients with MBC who had never received trastuzumab (HR = 0.493, 95% CI: 0.372-0.576) than for those who had received adequate trastuzumab therapy in EBC stage (HR = 0.878, 95% CI: 0.506-1.431).

CONCLUSION: This study showed great disparities in trastuzumab use in different regions and different treatment stages. Both EBC and MBC patients can benefit from trastuzumab, as the survival data show; however, when trastuzumab is adequate in the early stage, a further trastuzumab-based therapy in first-line treatment of MBC will be ineffective, especially for those with short disease-free survival, and a second line of anti-HER2 therapy will be recommended. (Research number: CSCO-BC RWS 15001).

IMPLICATIONS FOR PRACTICE: This article explores the disparities in the rates of trastuzumab use due to the inequitable allocation of medical resources in China. The irrational use can be found both in resource-abundant regions and in resource-limited regions. Although trastuzumab-based therapy improved survival, the actual use of trastuzumab in the early stage of breast cancer may influence the subsequent therapeutic effect after metastasis. These findings from real-world research could help to optimize HER2 therapy after metastasis, especially in regions with limited access to these expensive targeted drugs.